Mobile Package 2010

TRAINING SECTOR GENERAL DEPARTMENT FOR

PLANNING & DEVELOPING PROGRAMS

Contents

- GSM Introduction

- CDMA Overview

- GPRS Introduction

- UMTS Introduction

- HSDPA for WCDMA



Sub-sections

GSM Introduction

Introduction 1

Transmission Principles 2

GSM PLMN 3

Procedures 4

Radio Interface 5

Appindex 6

GSM Introduction

Sub-section reference

Sub-section identification Pages1 Introduction 1 - 44 2 Transmission Principles 1 - 37 3 GSM PLMN 1 - 32 4 Procedures 1 - 38 5 Radio Interface 1 - 31 6 Appendix 1 - 14

This document consists of 196 pages.

Chapter 1

Introduction

Introduction

Introduction

Contents

2History 1 15 GSM 2 27Current Situation, Market & Trends 3

Introduction Siemens

1 History

Introduction

History

Fig. 1

2

Siemens Introduction

History of Mobile Communications

“Mobile Communication” is much older than many people think. There have beendiverse "acoustic and optic means of remote information transfer" in the most variedcultures and stages of civilization on all populated continents. The range ofinformation transfer was very limited and the quality of the messages was affected byouter conditions such as the weather. In order to increase the range of informationtransfer in these times, transit stations were in part systematically constructed.

Beginnings of Electronic Communications

� Telegraph: S.F.B. Morse: 1843 First experimental telegraph line: Washington -Baltimore

� Telephone: Phillip Reis 1861: First speech transmission by cable / A. G. Bell: 1876World Exhibition, Philadelphia

At first electronic communications was possible only via wire i.e. by means of fixed(immobile) connections, forerunners of today's Fixed Network Connections. Initiallyan operator ("switchboard girl") was needed to establish these fixed physicalconnections for the caller manually at the central office. The first automaticexchanges were first put into service in the mid-1920s.

Radio Communications

Radio connections were first used for Wireless Communications in the late 19thcentury; information was sent via "ether".

� 1873: J.C. Maxwell - electromagnetic wave theory

� 1887: H. Hertz - experimental proof of the existence of electromagnetic waves

� 1895: A. Popow - first receiver with antenna for weather reports

� 1895: G. M. Marconi - first wireless transmission using spark inductor generatedHF waves (Morse code)

� 1897: “Marconi Wireless Telegraphy Company" founded

� 1901: First transatlantic transmission (Marconi)

� 1903: "Deutschen Telefunken GmbH" founded by AEG and Siemens & Halske

� 1906: First speech & sound transmission (Lorenz AG / Deutsche TelefunkenGmbH)

� 1909: First radio broadcast (New York, Caruso)

3



The beginnings: "archaic mobile communication"

• visual transmission (smoke/light signals,...)

• audible transmission (drums, horns,...)

Electronic

communication:

"terrestrial network"

• Telegraph 1st telegraph line 1843

Washington - Baltimore

• Telephone

P. Reis 1861

A.G. Bell 1876 World Exhibition Philadelphia

Radio transmission:1873 Maxwell‘s theory of electromagn. waves

1887 H. Hertz: experimental proof1895 Marconi: 1st wireless transmission1901 1st transatlantic transmission

1903 Dt. Telefunken GmbH: AEG, Siemens& Halske1906 1st speech and sound transmission1909 1st radio broadcast

1917 1st mobile transmission: radio station - train

History of Mobile Communications

Fig. 2

4


Connection Types

There are two principles for radio connections:

Simplex Connection

Simplex connections are a "one-way street" for communication in the form of (mostlyfixed) transmitters and mobile receivers. This has been realized as e.g. (broadcast)radio and television. But simplex connections are also used for direct communicationexchange i.e. two-way communication using stations which can be used both as atransmitter and a receiver (e.g. walkie-talkies). However the equipment (transmitting /receiving stations) cannot transmit and receive simultaneously. The call cycles or callintervals are determined by prior agreement or personal code words ("over").

Duplex Connections

Duplex connections signify two-way communication. Users can transmit and receivemessages simultaneously. An example of an early duplex connection is radiotelegraphy.

Simplex Connection:transmit or receive

Duplex Connection:simultaneous

transmission and reception

Over

Fig. 3

5



Single Cell Systems

The first Mobile Telephone Service to offer duplex connections comparable to fixednetwork based telephone services started in 1946 as a car phone service in St.Louis, Missouri. Comparable mobile telephone services appeared in post-war Europesome years later.

Problems in early mobile (car) telephone services (late 1940s/early 1950s):

� An operator was needed to connect calls within the wireless network.

� The equipment required was extremely heavy, bulky (therefore only feasible as acar phone service) and expensive.

� The service range was limited to the area that could be covered by a singletransmitting or receiving station (single cell system).

� The HF frequency range available was (is) very limited; it had to be (and still hasto be) distributed among competitors (e.g. the military, radio, and television).

The result was limited capacity, rapid market saturation, high equipment costs andlow service quality.

• Car telephone service

• Since the late 40‘s

• Low service and speech quality

• Heavy, bulky and expensive equipment

• Small coverage area

• No handover

• Manual exchange

• Low capacity

First Mobile

Services:

Single Cell Systems:

Fig. 4

6



Innovations in Mobile Radio Communications

Technical Innovations / Equipment

Fast development of new technologies such as semiconductor technology, diodes,transistors, integrated circuitry, microprocessors,...

� automatic switching

� reduction of hardware costs

� reduction of size and weight of equipment (in the 1950s/1960s a car phone tookup half of a car trunk; 1988: introduction of the mobile phone)

but:

� very limited telephone network capacity.

During the 1970s large-scale integrated, electronic applications and the developmentof microprocessors made the configuration of more complex systems possible. Oneresult of this was the development of single-cell transmitter systems with multiplereceiving stations. This made it possible to extend the range of the supply area, i.e.the operational range of the subscriber because the mobile station's transmitterpower limits the size of the cell in Single Cell Systems. However no increase incapacity resulted from this.

Cellular Mobile Radio Systems

The breakthrough in capacity, which resulted in a significant increase in the numberof subscribers, was achieved with the introduction of the Cellular Radio System in thelate 1970s/early 1980s. The coverage of the supply area of a mobile communicationoperator involves many radio cells with cellular radio systems, in which theaforementioned limitation of the available HF frequency range is neatly circumventedthrough the repeated use of the HF channels.

7



Quantum Leap in Mobile Communications:

Single Cell Systems �� Cellular Systems

radius

r

re-use distance

r

Single Cell

System

Cellular

System

Fig. 5

8


First Generation (1G) Cellular Mobile Radio Systems

Information transmission of first generation cellular mobile radio system takes placevia analogue radio interface. These systems were tested in many countries in the endof the 70s.

In 1979, mobile services were introduced for commercial operation; in the USA,AMPS (Advanced Mobile Phone Service), and in Japan, NTT-MTS (NipponTelegraph & Telephone Co.).

In the early 80s, the NMT (Nordic Mobile Telephone) was introduced in Scandinavia,in 1985 TACS (Total Access Communication System) was introduced in England andthe C450 System in Germany.

First Generation Cellular Mobile Radio Systems

Country System Frequency range[MHz]

Introduced

in year

USA AMPS 800 1979

Japan NTT-MTS 800 1979

Sweden, Norway,Finland, Denmark

NMT 450, 900 1981 - 86

Great Britain TACS 900 1985

Germany C450 450 1985

France Radiocom2000

NMT

450

900

1985

1989

Italy RTMS

TACS

450

900

1985

1990

Fig. 6

9



Second Generation (2G) Cellular Mobile Radio Systems

A further and very significant innovation in mobile radio communications took placewith the introduction of the second generation cellular mobile radio system (e.g.GSM) in the early 90s. Transmission via radio interface is now digital. Along with asignificant improvement of transmission quality and expansion of services, there hasbeen a considerable increase in capacity. The increase in subscribers led to moreconvenient, lighter and less expensive equipment with a wide range of possibilitiesfor use.

Portable Mobile Equipment

Mobile phones were first introduced in 1988. The weight of the equipment decreasedfrom 1 kg to less than a

100 g within few years. At the same time, mobility clearly improved despitedecreasing weight owing to improvements in rechargeable batteries. Standby timesof more than 5 days can be achieved.

2nd Quantum Leap:

Analog (1st Generation) �� Digital (2nd Generation)

Different Generations of Mobile Stations

Second generation

GSM mobile telephones Second generationGSM mobile telephones

Digital GSM technology.Terminal devices are handier

and have greater battery capacity.

Digital GSM technology.Terminal devices were less

bulky, but still too heavy(battery capacity problems).

Analog technology.Terminal devices were

bulky and heavy.

First generation

mobile telephones

for fixed vehicle installation and

analog mobile telephones

Fig. 7

10



Example: Mobile Subscriber in Germany

Since the early 50s there have been several regional networks at 30, 80, 100 MHz.They were allocated only to public authorities and organizations with security tasks.The regional networks (DBP) were combined in the so-called A-network in 1958 al-lowing private use for the first time.

A-network: in operation: 1958 - 1977; frequency range: 156 - 174 MHz; in thebeginning 16, later 37 radio carrier; analogue transmission, manual switching; max.11,000 users (1971); closed in 1977; its frequencies were transferred to the B-network.

B-network: in operation: 1972 - 1994; frequency range: 146 - 164 MHz; from 1977 to174 MHz (from A-network); in the beginning 38, later 75 radio carrier; analoguetransmission, automatic switching; max. 27,000 users (1986); problem: max.capacity, no further channels; closed in 1994.

C-network (C450): in operation: 1985 - 2000; frequency range: 451.3 - 455.74 MHz& 461.3 - 465.74 MHz; 222/287 radio charier; system technology: Siemens. TheC450 system was the first German cellular system and led to an enormous increaseof subscribers (max. 850,000 users). The C-network was similar in structure tomodern digital networks.

D-networks (GSM900): Introduction in 1992 (D1 & D2); 900 MHz frequency range (+minor extensions in the 1800 MHz range from 1999 on; system technology partlyfrom Siemens (D900).

E-networks (GSM1800): Introduction in 1994 (Eplus) and 1998 (E2); 1800 MHzfrequency range; System technology partly from Siemens (D1800).

The digital D and E networks, being GSM900 / GSM1800 networks, led to a rapidand steady increase of the number of subscribers in Germany. In 12/2000, a total of46 million mobile subscribers were registered in the 4 networks, D1, D2, Eplus & E2.

11



0,01

0,1

1

10

100

Su

bs

cri

be

r [M

.]

1978

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

Year

Germany

Subscriber trends (Example): Germany 1978 - 2000

B-n

etw

ork

in

tro

du

ctio

n

C-n

etw

ork

in

tro

du

ctio

n GS

M (

D1,

D2)

intr

odu

ction

GS

M (

Ep

lus)

intr

odu

ction

GS

M (

E2

) intr

odu

ction

Fig. 8

12


Limits of the First Generation Mobile Radio Systems

1. Capacity: The capacity limits of analogue technology are reached quickly evenwith cellular networks. The demand increases with the offer and the sinkingprices. A number of 850,000 subscribers, i.e. the maximum capacity of theanalogue C-network, corresponds to less than 7 % of the mobile subscribers in1998 (only 6 years after introducing digital networks). The capacity of digitalnetworks has not yet been exhausted.

2. Quality: A second problem was the often inadequate transmission quality of theanalogue systems, which increased with the distance of the mobile subscriber. Adetailed description and discussion of the problems regarding the transmissionquality or the disadvantages of the analogue system in comparison to digital onecan be found in the next chapter.

3. Incompatibility: One or more analogue networks on frequency bands 450/900MHz existed in most European states in the late 1980s. Every one of thesenetworks formed a mobile communication island since the individual standards ofthese networks were incompatible in most cases (or still are, as far as they stillexist); they prevented mobile phone traffic across borders (InternationalRoaming). Europe thus looked liked a rag rug of incompatible systems.

The limits of existing analogue systems

1. Capacity: the number of potential mobile phone customers is larger than theexpected capacity of analogue systems,

2. Quality: insufficient transmission quality with increasing distance between themobile station and the base station,

3. Incompatibility: between different national standards,

were already recognized since the early 80s and were discussed on an internationalEuropean level. The need to develop a new, standard cellular system for Europe wasacknowledged.

The GSM Standard was developed for this purpose.

13



� Capacity� Quality� Incompatibility

European mobile

communication marketearly 90‘s

1G Limitations

Fig. 9

14


2 GSM

Introduction

GSMGlobal System for

Mobile Communications

Fig. 10

15


The GSM History

The foundation for the GSM Standard was laid already in 1978, four years before thename GSM was established. In 1978 the CEPT reserved a frequency range round900 MHz for mobile communications in Europe. The limits of analog mobilecommunications in Europe were recognizable in the early 80s. At that time the firstanalog cellular networks were just beginning their operation and were still far fromtheir maximum capacity. Despite this a group of experts was formed to establish thelonger-term challenges of mobile communications and to develop a new bindinginternational standard for digital mobile communications in Europe. Thus the GSMStandard became undoubtedly one of the most successful European products of thepast decades; its sphere of influence is extended far beyond the originally plannedEuropean scope.

Milestones of the GSM Standard

� 1982: The CEPT forms a team of experts, the Group Special Mobile (GSM) withthe purpose of developing a binding international standard for mobilecommunications in Europe.

� 1984 – 86: Various technical possibilities are compared in order to achieve anoptimal utilization of the predefined frequency ranges.

� 1986: A permanent core of experts is employed.

� 1987: Main transmission principles are selected; 13 countries agree in the MoU(Memorandum of Understanding) to start GSM networks until 1991.

� 1988: The ETSI (European Telecommunication Standards Institute) is founded;most of the standardizing activities of the CEPT, including GSM, are assumed bythis new body. Along with state-owned operators, industry, private networkoperators and consumer groups participate in the ETSI, too.

� 1989: GSM is renamed from "Group Special Mobile" to "Global System for MobileCommunications".

� 1990: GSM900 Standard (Phase 1) is adopted. DCS1800 Standard (Phase 1) isdeveloped as first GSM adaptation. The first GSM systems are in test operation.

� 1992: Commercial introduction of many large GSM900 networks.

� 1993: Work begins on updating the GSM900/DCS1800 standards: GSM Phase 2.

� 1995: GSM-R (Railway): The ETSI reserves further frequency range for a railwaynetworks; first test projects are started. GSM Phase 2 work is completed.

� 1996: Worldwide success of GSM Standard; used in more than 50 countries.PCS1900 (Public Cellular Systems) as further GSM adaptation in the USA.

16



GSM Milestones

1978 CEPT reserves 2 x 25 MHz in 900 MHz range

1982 CEPT founds "Groupe Special Mobile" GSM

1984-86 Comparison of technical possibilitiesGoals: - free roaming

- international accessibility under 1 number (international roaming)- large network capacity (bandwidth efficiency)

- flexibility � ISDN- broad service offering- security mechanisms

1986 Core of experts meets continuously

1987 Selection of central transmission techniques

Memorandum of Understanding: MoU

1988 ETSI founded

1989 GSM � Global System for Mobile Communication

1990 GSM900 Standard (phase 1)

1991 DCS1800 adaptation

Trials / "friendly user" operation

1992 Start of commercial operation

1993 Beginning of work on phase 2

1995 Completion of work on phase 2 (GSM900/DCS1800)

Reservation of GSM-R frequencies (ETSI)

1996 PCS1900 adaptation (USA)

Fig. 11

17


� 1997: GSM Phase 2+ Annual Release ‘96: CAMEL Stage 1, ASCI for GSM-R.DCS1800 / PCS1900 are renamed to GSM1800 / GSM1900. Dual bandequipment for GSM900 / GSM1800; 10 years of MoU: 109 countries; 239operators; 44 million GSM subscribers; 28 % share of the world market.

� 1998: Phase 2+ Annual Release ‘97: HSCSD, GPRS Stage 1, CAMEL Stage 2,...08/98: 100 million GSM subscribers in 120 countries; 35 % share of the worldmarket; GSM is quasi world standard. GSM-R networks in operation. World-wideservicing through co-operation with mobile satellite systems (IRIDIUM).

� 1999: Phase 2+ Annual Release '98; 250 million subscriber; 130 countries

� 2000: Phase 2+ Annual Release '99: GPRS Stage 2, CAMEL Stage 3, EDGE,Virtual Home Environment VHE, Adaptive Multirate speech AMR,...GSM Rel. '99services identical to UMTS Rel. '99 (first UMTS release); 410 million subscriber;161 countries; approx. 60% of world-market

1997 Phase 2+: Annual Release `96

DCS1800 / PCS1900 � GSM1800 / GSM1900

Dual-band devices

GSM: practical world standard (109 countries/regions; 28 % market share)

1998 Phase 2+: Annual Release `97: GPRS, CAMEL,....

First GSM-R networks

World-wide accessibility using dual mode GSM/IRIDIUM

35 % of world market

1999 Phase 2+: Annual Release ‘98

250 M. subscriber, 130 countries

2000 Phase 2+: Annual Release ‘99: AMR, VHE,... identical to UMTS Rel. ‘99

60% of world market; 410 M. subscriber, 161 countries

GSM Milestones

Fig. 12

18



The GSM Technical Guideline

Objective (1982): Development of a unified, international standard for mobilecommunications. Guideline from the start:2 x 25 MHz frequency bands at 900 MHzare reserved by the CEPT for mobile communications in Europe in 1978. 1982:Roaming; the user can change location, keep the connection and be reached in theentire range of a PLMN and in the entire GSM range (International Roaming) as longas roaming agreements have been made. One user - one number; the subscribercan be reached at a single personal number in the entire GSM range, i.e. in variouscountries and PLMNs.

Late objectives: Maximum flexibility to other services, e.g. ISDN (Integrated ServicesDigital Network; 1984) Vast service offers, i.e. technical possibilities of the PSTN/ ISDN and special features of mobile communications Safeguarding frominterception and subscriber license fraud; data protection.

The GSM Recommendations

The GSM Standard is a consistent and open standard for cellular mobilecommunication systems established by the ETSI. All aspects of the realization of theGSM Standard have been established in now more than 150 recommendations(technical specifications). Subsystems, network components, interfaces, signaling,tests and maintenance aspects etc. are described. This allows a harmoniousinteraction of all elements of a mobile communication network designated as PLMN(Public Land Mobile Network). At the same time the Recommendations are flexibleenough for the different realizations of various vendors. The Recommendations areorganized into 12 series according to different aspects. This structure reflects thestructure of the PLMN system and its interfaces.

19



GSM Recommendation

MSC

PSTN

ISDN BSS MS

Series 01: General

Series 02: Service Aspects

Series 03: Network Aspects

Register

Series 04:

MS/BS Interface

& Protocols

Series 05:

Um Radio

Transmission

Series 06:

Speech Coding

Series 067:

Terminal

Adaptors for MS

Series 08:

MSC-BSS Interface

Series 09:

Network Interworking

Series 10:

Service Interworking

Series 11: Equipment & Type Approval Specifications

Series 12: Operation & Maintenance

12 Series; each max. 100 Rec.:e.g. GSM Rec. 08.07

Fig. 13

20


The Evolutionary Concept

The GSM Standard consists of multiple of recommendations. They are organized byvarious aspects and already comprised 5230 pages when the first phase wasadopted in 1990. It was originally planned to comprise every specification in the GSMStandard (with the exception of “half rate speech") from the start, i.e. when thestandard was adopted. In 1988 it was recognized that not all of the planned servicescould be specified in the expected time frame. This led to the important decision toleave the GSM Standard incomplete and to leave space for further modifications andtechnical developments. This evolutionary concept secures for GSM the possibility ofpermanently adapting to the requirements of the market and thus ensures of notbecoming old-fashioned within a couple of years owing to the extremely fastdevelopment in this market sector.

GSM Phase 1

The Phase 1 standardization was closed in 1990 for GSM900 and in 1991 forGSM1800. The implementation of GSM systems Phase 1 comprises all of the mostimportant prerequisites for digital information transmission. Speech transmission is ofthe greatest importance here. Data transmission is also defined by data transmissionrates of 0.3 to 9.6 kbit/s. GSM Phase 1 comprises only a few supplementary servicessuch as call forwarding and barring.

GSM Phase 2

The Phase 2 standardization work started shortly after completion of Phase 1 andwas closed in 1995. In Phase 2 Supplementary Services comparable to ISDN(Integrated Services Digital Network) were included in the standard. Technicalimprovements have been specified, e.g. the Half Rate Speech. In Phase 2, thedecision on future downward-compatibility with older versions is of high importance.

GSM Phase 2+

GSM Phase 2+ refers to a “smooth” transition in contrast to Phase 2. A new completeupdate of the GSM Standard is not planned. Individual topics are discussedseparately and the update is added to the GSM standard in Annual Releases. Maintopics are new Supplementary Services as the ASCI services (Advanced SpeechCall Items). Furthermore, the IN feature Customized Applications for Mobile networkEnhanced Logic CAMEL and Virtual Home Environment VHE are very important.Especially the introduction of features to achieve higher data rates, i.e. HSCSD (HighSpeed Circuit Switched Data), GPRS (General Packet Radio Service) and EDGE(Enhanced Data rates for the GSM Evolution) has received much attention. GSMPhase 2+ thus paves the way to 3G (UMTS).

21



Phase 1Phase 2

Phase 1

Phase 2+

Phase 2

Phase 1

Services

Year1991 1995 1997

Full Rate Speech (FR),

Standard services

Data: max. 9.6 kbit/s

New services e.g.

MTPy, CUG, AoC;

Half Rate Speech (HR)

New services e.g.

ASCI, SOR, UUS

EFR;

IN: CAMEL

Data: HSCSD, GPRS,

EDGE (> 100 kbit/s)

Annual Releases !

GSM: Evolutionary Concept

Downward compatibility

MTPy:

CUG:

AoC:

ASCI:

SOR:

UUS:

EFR:

IN:

CAMEL:

HSCSD:

GPRS:

EDGE:

Multiparty Service

Closed User Group

Advice of Charge

Advanced Speech Call Items

Support of Optimal Routing

User to User Signalling

Enhanced Full Rate Speech

Intelligent Network

Customized Applications for

Mobile network Enhanced Logic

High Speed Circuit Switched Data

General Packet Radio Service

Enhanced Data Rates for the GSM

Evolution

Fig. 14

22


Adaptations of the GSM Standard

The GSM adaptations GSM900, GSM1800, GSM1900, GSM-R and GSM400 differ inthe frequency ranges used and the resulting different technical implementations.

GSM900 (GSM, E-GSM)

Originally 2 x 25 MHz in the frequency range around 900 MHz (890 - 915; 935 - 960MHz) were provided for mobile communication applications. In an extension of thisrange, called E-GSM (Extended GSM) these ranges will be increased to 2 x 35 MHz(880 - 915; 925 - 960 MHz) on a national level when further operation licenses expire.

GSM1800 (DCS1800)

As an adaptation of the GSM900 Standard the DCS1800 Standard (Digital CellularSystem) was introduced in 1991. The DCS1800 was a British initiative with theintention of opening mobile communications to all sections of population as a “massmarket”, especially in urban areas. The GSM1800 has 2 x 75 MHz in the frequencyrange around 1800 MHz (1710 - 1785; 1805 - 1880 MHz). In 1997 the designationDCS1800 was changed to GSM1800 in order to clarify the common standard.

GSM1900 (PCS1900)

The PCS1900 Standard (Public Cellular System) is the American branch of the GSMStandard since 1995/96 in the frequency range around 1900 MHz. The frequencyrange available between 1850 - 1910; 1930 - 1990 MHz in the USA was split up in1995 and auctioned off to different net-work operators. In 1997 the PCS1900 wasrenamed GSM1900 in order to clarify the common standard.

GSM-R (Railway)

For mobile communication of railway operators 2 x 4 MHz in the frequency range of876 – 880 MHz & 921 – 925 MHz have been reserved.

GSM400

With Rel. '99 the frequency ranges between 450.4 – 457.6 MHz & 460.4 – 467.6 MHzrespectively the ranges (of former 1G systems) between 478.8 – 486 MHz & 488.8 –496 MHz are foreseen for GSM400. The GSM400 frequency range enables largearea cells for rural environment.

23



876 880

890

GSM

900

915 921 925

935

960 1710 1785 1805 1850

1880

1910 1930 1990[MHz] [MHz]

GSM

900

E-GSM E-GSM

GSM

1800

GSM

1800

GSM

1900

GSM-R GSM - Adaptations

GSM

1900

Frequency Range[MHZ]

Useable HFchannels

Application Area

GSM400 450.4 – 457.6 / 460.4 – 467.6

478.8 – 486 / 488.8 - 496

35 rural environment

GSM900E-GSM

890 - 915 / 935 - 960880 - 915 / 925 - 960

124174

Worldwide exceptAmerica

GSM1800 1710 - 1785 / 1805 - 1880 374 Worldwide exceptAmerica

GSM1900 1850 - 1910 /1930 - 1990 299 America

GSM-R 876 - 880 / 921 - 925 19 Railway systems

Fig. 15

24


The GSM-PLMN

In the GSM System there must be a distinction between network operator, provider oftelecommunication services, supplier of terminal equipment and manufacturer ofnetwork components. Especially the sale of telecommunication services and terminalequipment differs from the conventional fixed network and mobile communicationnetwork of the first generation, in which state-owned network operators, serviceproviders and equipment suppliers usually form a monopoly. In GSM the actualnetwork operator often transfers services to private providers who supply theservices to the mobile subscribers under different conditions. With the wide range ofproducts there is also great competition in the field of mobile equipment as well as ofmobile communication network components which should force further technicaldevelopment and keep the prices down.

PLMN - Public Land Mobile Network

A PLMN is a terrestrial mobile communication network set up and run by public andprivate operators. It is used to provide public mobile communication services.

General Objectives of a GSM-PLMN (with respect to service aspects):

a) Provision of a wide range of speech and non-speech services andcompatibility to those services offered in fixed telecommunication networkssuch as PSTN, ISDN and PDN;

b) Additional provision of specific services for mobile access environment;

c) Compatible access for mobile subscribers in all countries where the GSMSystem is operated;

d) Provision of roaming (roaming agreement) and automatic updating;

e) Location registration of mobile subscribers in these countries;

f) Provision of sufficient quality of service;

g) Provision of services with a wide range of mobile stations, e.g. permanently in-stalled in vehicles, so-called portables and hand stations (mobile phones).

General Objectives of a GSM-PLMN (with respect to performance aspects):

a) Guarantee of a high spectrum efficiency;

b) Provision of a system concept which will lead to attractive costs regardinginfra-structure and mobile equipment

25



GSM-PLMN(Public Land Mobile Network)

Example:

Germany

Competition concept:different network operators,

providers and manufacturers

D1Telekom

D2Mannesmann

Eplus

E2Viag Intercom

Fig. 16

26


3 Current Situation, Market & Trends

0,01

0,1

1

10

100

1000

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

Introduction

Current Situation,

Market & Trends

Fig. 17

27


Overview: Systems/Standards

At the time there is a wide spectrum of mobile communication systems of the first andsecond generation along with the GSM Standard and its adaptations. Importantexamples include:

� Paging Systems

� Cordless Telephone

� Wireless Local Loop

� Private Mobile Radio

� Cellular Mobile Systems

� Mobile Satellite Systems

These different systems differ in:

� Target groups

� Services offered

� Prices

� Coverage

� Degree of mobility

� Technical principles / realization

28



analogue cordless telephone systems

e.g. CT1, CT1+

digitalpaging systems

e.g. ERMES

analoguepaging systems

e.g. Citycall

Cordless

telephone booth

digital cordless telephone systems

e.g. DECT, PACS, PHP

analoguePrivate Mobile Radio

PMR

Wireless Local Loop

WLL

digitalPMR

e.g. TETRA

digital cellular systems

e.g. GSM, D-AMPS,

PDC, IS-95

digital satellite systemse.g. IRIDIUM, ICO,

Globalstar

analoguecellular systems

e.g. C450, NMT, AMPS

analoguesatellite systemse.g. INMARSAT

Current

Mobile

Communication

Systems

Differences:• target groups

• services offered

• prices

• coverage

• degree of mobility

• transmission technique

• ...

1G 2G

Fig. 18

29


1G Systems

C450: closed 12/2000

TACS (Total Access Communications System): closed 2001.

NMT (Nordic Mobile Telephone): closed 2001.

AMPS (Advanced Mobile Phone Service): The AMPS system was introduced in 1979in the USA. The system, operated in the frequency range of 800 MHz, was the mostsuccessful mobile radio system in the world until 1997. It still has an increasingnumber of subscribers, because of its large coverage in the USA. 12/2000, more than75 million AMPS subscribers were registered.

2G Systems

GSM (Global System for Mobile Communications): The GSM Standard wasadopted as the first digital mobile communication standard, as planned since theearly 80s. Commercial operation started in 1992. This led to the world-wide use ofGSM net-works, which were originally planned for the European system, in more than120 countries and regions. GSM uses a hybrid solution of FDMA and TDMA as anaccess technique. GSM used currently 900 / 1800 /1900 frequency ranges.

D-AMPS (Digital Advanced Mobile Phone System): The D-AMPS was conceivedas a supplementary system to the successful analogue AMPS in the USA andCanada. The commercial start was 1991/92. D-AMPS as IS-136 standard is basedon a combined FDMA/TDMA access technique. It shares the 800 MHz range withAMPS (824 - 849; 869 - 894 MHz). It expanded to the 1900 MHz range in 1995.Multimode / multiband equipment is used for AMPS/D-AMPS.

PDC (Personal Digital Cellular): With the influence of D-AMPS, PDC (originallycalled JDC - Japanese Digital Cellular) was standardized for the Japanese market.The commercial start was 1993/94. A combined FDMA/TDMA procedure, similarly tothe D-AMPS, is used as an access procedure. Mobile stations transmit at the higherfrequency with PDC, in contrast to all other systems. Frequencies around 900 MHz

(810 - 826; 940 - 956 MHz) & 1500 MHz (1429 - 1453; 1477 - 1501 MHz) are used.

IS-95 CDMA IS-95 CDMA was developed in the early 90s based on CDMA spreadspectrum digital technology and was declared IS-95 standard in 1993. Thecommercial start was 1995/96. IS-95 CDMA networks are emerging world-wide withemphasis on North America and Eastern Asia. Frequencies in the 800 MHz and 1900MHz range are used world-wide, and also in the 1700 MHz range in Korea.

30



Cellular Systems

First generation:C450

NMT - Nordic Mobile Telephone

TACS - Total Access Communications SystemAMPS - Advanced Mobile Phone System

Second generation:

GSM D-AMPS PDC IS-95

Start 1992 1991/92 1993/94 1995

Coverage worldwide especiallyUSA, Canada

Japan especially USA,Canada, EasternAsia

Frequency

ranges [MHz]

900 / 1800 /1900 (America)

800 / 1900 900 / 1500 800 / 1700 (Korea) /1900

Multiple

Access

TDMA / FDMA TDMA / FDMA TDMA / FDMA CDMA

Speech [kbit/s] 13 / 5.6 7.95 6.7 9.4 / 13

Data (max.)

[kbit/s]

9.6(n•14.4; n = 1...8)

4.8 4.8 9.6 / 14.4

Subscribers

(02/2001)

~ 410 million ~ 35 million + 75 million (AMPS)

~ 55 million ~ 85 million

Fig. 19

31


Mobile Satellite Systems MSS

Large areas of the earth's surface can not be covered by fixed or mobile networks.Mobile Satellite Systems MSS are offered for supplying scarcely populated regionsand areas with weak infrastructure. Satellite supported mobile communicationsystems are useful for high-sea ship transport, for catastrophe regions, and foremergency supply.

Satellite systems can be distinguished with respect to their orbits:

� GEostationary Orbit - GEO, with approx. 36,000 km altitude;

� High Elliptic Orbit - HEO;

� Medium Earth Orbital - MEO, from 10,000 - 20,000 km;

� Low Earth Orbital - LEO, from 700 - 1,500 km.

1G MSS

MARISAT (Maritime Satellite): MARISAT went into operation in 1976 as the firstmobile satellite system, initiated by the USA.

INMARSAT (International Maritime Satellite Organization): INMARSAT is taking adominant role in 1G MSS. Founded in 1979, it is used by more than 100 membershipcountries. The four INMARSAT (operation) satellites are in a geostationary orbit(about 36,000 km altitude). With the exception of a the pole caps, a globaltransmission to the world is achievable. Digital transmission is via INMARSATsatellites since 1995., i.e. INMARSAT has turned over to a 2G MSS system

2G MSS

Digital information transmission and a larger number of satellites in lower orbits (LEOand MEO satellites) allow considerably higher capacity. Several services similar tothose of GSM should be possible. A problem of the 2G systems is the comparablehigh price and fast extension of 2G terrestrial networks

� Iridium (closed 2000)

� Globalstar

� ICO

� Ellipso

� ORBCOMM

� Teledesic

� Skybridge

32



Supply to/ in case of:

- inaccessible, underpopulated areas

- poor infrastructure- high seas- catastrophe areas

- failure of other supplies

Supply to/ in case of:Supply to/ in case of:

- inaccessible, underpopulated areas- poor infrastructure

- high seas- catastrophe areas- failure of other supplies

GEOGEostationary Orbit

10,000- 20,000 km

700- 1,500 km

MEO MediumEarth Orbit

approx.36,000 km

LEOLow Earth Orbit

Mobile Satellite Systems MSS

HEOHigh Elliptic

Orbit

1G:

MARISAT (USA) since 1976

INMARSAT (International Maritime

Satellite Organisation):• since 1979; > 80 member countries• 4 GEO satellites;• global access

2G:• Iridium, ICO, Globalstar

• private MSS operator• speech- & low data rate services

Earth

Fig. 20

33


The Mobile Market: Subscriber Trends 1980 - 2000

Before the introduction of first generation of cellular mobile communication systems,the mobile communication market was unimportant. One-cell systems had only a fewthousand subscribers and slow annual growth rates in Europe, North America, andJapan. Until the introduction of the first cellular systems in 1979 (AMPS: USA, NTT-MTS: Japan) fewer than a million subscribers were registered worldwide.

The introduction of the first generation (analog) cellular mobile communicationsystems led to a quantum leap on the mobile communication market. There wereannual growth rates of 10 to more than 50 %. In the early nineties, there were morethan a million subscribers registered in both the USA (AMPS) and Great Britain(TACS) each. Several hundreds of thousands of subscribers were registered in othercountries with systems such as NMT, C450, NTT-MTS. The number of worldwidesub-scribers exceeded 10 million in 1990. Simultaneously the limits of analoguecellular systems were apparent in many countries owing to capacity problems,especially in densely populated urban regions.

The introduction of GSM as the first mobile communication standard of the second(digital) generation allowed an improved transmission quality, a larger offer ofservice, various technical / organizational improvements, and a considerably moreefficient use of radio interface resources. A significant increase of capacity and thusfurther growth of the mobile communication market became possible. Already shortlyafter the start of GSM in 1992, subscriber numbers exceeded the million mark inmany countries. Other digital systems such as IS-95 followed. A development to agenuine mass market has been evident since the introduction of the secondgeneration of mobile communications.

34



0,01

0,1

1

10

100

1000

Su

bs

cri

be

r [M

.]

1980

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

Year

Germany

World

Subscriber trends:

1980 - 2000

1G

IntroductionSingle cell

systems

2G

Introduction

Fig. 21

35


Trends & Outlook

The mobile communication market will expand greatly in the future as well. Incontrast to the fixed network sector, which has developed slowly in the past decadesand has only recently become more dynamic, many predict unhindered growth for themobile communication sector beyond the year 2000. Only the growth of the Internetis expected to exceed the growth of the mobile communication sector. It is generallyexpected that the number of the mobile communication subscribers will rapidlyapproach that of the fixed subscribers, and that in regions with a poorly set up infra-structure, the number of mobile communication subscribers will clearly exceed that offixed subscribers within the foreseeable future.

Almost three billion mobile communication subscribers world-wide are expected by2015. This growth is apparent in the currently developing countries and newlyindustrialized countries of the Asian / Pacific region. A 50 % share of the worldwidemobile communication market is expected for the Asian / Pacific region by 2015; forindustrial nations in North America and Europe (EU15), a share of only about 7 % -11 % is expected.

0'

500'

1000'

1500'

2000'

2500'

1995 2000 2005 2010 2015

RoW

As ia / P ac ific

North A m eric a

EU 15

UMTS Forum

Report #1

Trends & Outlook

Su

bscri

ber

[M.]

Year

Fig. 22

36



Mobile Trends

The mobile radio systems of the second generation have been optimized for speechtransmission. Data transmission is possible, but has previously been consideredsecondary. Taking the increasing mobility in the professional world (work outside theoffice, telework) into consideration, the need for mobile transmission of data is in-creasing. Comparatively user-unfriendly terminals (adapter solution) and relativelylow data transmission rates are problems for data transmission of the secondgeneration of mobile communications. The data rates for GSM are between 0.3 - 9.6kbit/s, the transmission rates of other cellular standards are comparable or less. Thefirst mobile satellite systems of the second generation also have only low datatransmission rates (Iridium max. 2.4 kbit/s, Globalstar max. 9.6 kbit/s). These ratesare considerably lower than those of ISDN (64 kbit/s).

A large variety of demands are being placed on future mobile communications. Alongwith improved world-wide service, user friendliness and cost reduction, mobile PCInternet connection with a high data transmission rate is required.

Many of these demands are taken into account in GSM Phase 2+.

In this way bearer services were standardized with transmission rates in order to in-crease data transmission rates as well as to realize “mobile computing” and accessto the Internet. Data transmission rates can be adapted to the transmission rates ofISDN and can be increased significantly further (up to more than 100 kit/s) by meansof these bearer services. User friendly equipment and cost-reduced features are alsoplanned, such as improvements in speech quality and world-wide availability bymeans of satellite roaming. Furthermore flexible services adaptable to customer re-quests and intelligent network services are planned.

37



Trend:

Voice �� Data

Mobile Trends

Source:

UMTS Forum

0

20

40

60

80

100

Tra

ffic

[%

]

1996 2001 2005 2007

Year

Voice

DataRequirements:• high data rates

• user-friendliness

• improved service offering

• cost reduction

• worldwide accessibility

GSM Phase 2+• data rates > 100 kbit/s

• mobile computing, Internet

• new, integrating ME

• new flexible services + IN

• satellite roaming

• & much more

Fig. 23

38


Mobile Forecast (Europe)

10 % of the traffic is expected to be on the data transport radio interface already in2001, 30 % in 2005.

If further capacities and higher data transmission rates are achieved, there are hardlyany limits to a further growth of the mobile communication market even after thenumber of subscribers reaches saturation.

The market share of speech transmission is as of 2007 expected to be less than 50% in the entire volume of traffic.

An enormous change in the proportion of speech transmission to data transmissionhas thus been predicted in the use of mobile communications in the first decade ofthe 21st century.

It will be expected

� change from speech to data transmission

� high data rate multimedia applications.

Predictions assume a minor but slowly increasing share of multimedia users inEuropean mobile communications after the implementation of GSM Phase 2+features, HSCSD and GPRS (as of 2000).

This is also the limit of GSM. Although the performance capacity of GSM Phase 2+far exceeds the original expectations for the second generation of mobilecommunications, neither the frequency ranges available nor the narrow-bandfrequency use in GSM suffice for the predicted increases and demands regardingdata transmission, especially multimedia use.

The third generation of mobile communications with GSM's successor, the UMTS(Universal Mobile Telecommunications System) is to deal with these applications anddemands as of 2002.

A considerable increase in multimedia use is expected with a wide-range expansionof UMTS as of 2005. Predictions of the UMTS forum assume that of the approx. 260million European mobile communication subscribers in 2010, approx. 90 million couldbe multimedia users, while the rest of the users use only speech and low data rateservices. Multimedia users will produce more than 50 % of the entire traffic rate.

39



Mobile subscriber

(total)

Mobile subscriber

all applications from

voice to Multimedia

Mobile subscriber

Speech only/

low data rates

Mobile communication

forecast (Europa)

mobile Multi Media:

• Start with GSM Ph2+

• Breakthrough:

3G (UMTS)Source: UMTS-Forum

0'

50'

100'

150'

200'

250'

300'

1995 2000 2005 2010

Year

Su

bs

cri

ber

[M.]

Fig. 24

40


The Third Generation (3G)

There are at the time many mobile communication standards of both the second and(still) first generations. Cellular mobile networks of the most different standardscomplement one another or compete with private mobile radio systems, cordlessstandards, paging systems and satellite systems, etc. Every one of these standardshas specific features, advantages and disadvantages, applications and user circles.Many of these systems exist only on a national level and/or are incompatible. To acertain extent this scenario reassembles on a world-wide level the situation of thecellular systems in Europe before the introduction of GSM.

IMT-2000 (International Mobile Telecommunications 2000)

The third generation of mobile communications represents a world-wide system ofcompatible standards, in which the most various current and future demands ontelecommunications have to be dealt with. The main task is to provide services to thecustomer, independently of his location and the specific available infrastructure.Smooth mobility should be guaranteed over all operator-dependent, national andgeographic borders at any location.

The demands on the third generation mobile communication systems have beendiscussed since the early 90s under the term FPLMTS (Future Public Land MobileTele-communications Systems). The term FPLMTS was changed into a term easierto pronounce, IMT-2000, in the mid 90s for countries in which English is not a nativelanguage. IMT stands for International Mobile Telecommunications 2000 indicatesboth the approximate date of introduction and the frequency range.

The International Telecommunications Union - ITU - is responsible for the IMT-2000specification. IMT-2000 is planned as the world-wide guideline of all standards of thethird generation of mobile communications. All of the "regional" standardization unitsfor developing standards must fulfil the ITU stipulations for IMT-2000. This ensures acompatibility of the standards to be specified without hindering innovative individualdevelopment and competition.

Many regional standardization committees create their own standards under the IMT2000 "roof". Nevertheless, UMTS (Universal Mobile Telecommunication System) asGSM successor system is expected to dominate the 3G market

41



e.g. UMTS, cdma2000, UWC-136

2G(digital)

Paging Systems

e.g. ERMES

Cordless Telephonee.g. DECT, PACS, PHS

WirelessLocal Loops

WLL

PMRe.g. TETRA

Cellular systems

e.g. GSM, D-AMPS,IS-95, PDC

MSS

e.g. IRIDIUM, ICO, Globalstar

1G(analog)

Cordless Telephonee.g. CT1, 1+

Paging Systems,

e.g. City Call

wirelessTelephone cell

Private Mobile RadioPMR

Cellular systems


MSS

e.g. INMARSAT

3G

1 family of

standards

for all

• applications

• countries

different, incompatible standards for

different applications, countries & regions

IMT-2000

Fig. 25

42


UMTS - Universal Mobile Telecommunications System

The ETSI (European Telecommunication Standards Institute) has specified UMTS asthe successor of GSM; a forum call Third Generation Partnership Project 3GPP, co-operating with the most important standardization organizations of the world isresponsible since 12/98. UMTS will fulfil the requirements for IMT-2000.

With UMTS world-wide multimedia access is possible at any time to all ranges whichare currently operated by various mobile communication systems of the first andsecond generations.

Data rates of 8 kbit/s to 2 Mbit/s are to be supported. UMTS will support zone 1 – 3 ofthe four zones of the IMT-2000 concept:

� Zone 1 Indoor: for offices, private households,...; for low speed (stationary / up to10 km/h) max. data rates up to 2 Mbit/s are theoretically possible.

� Zone 2 Urban: for city, shopping malls, railway stations, subways, airport halls forlow speed (stationary / up to 10 km/h) max. data rates up to 2 Mbit/s aretheoretically possible.

� Zone 3 Suburban/Rural: For wide range mobility (car, train) with higher / highspeeds (up to 120 / 500 km/h), 384 kbit/s 144 kbit/s should be possible. (Remark:for UMTS only the lower speed value is currently planed)

� Zone 4 Global: For rural, thinly populated areas with low user densities. All speedsfrom stationary (individual buildings, measuring stations), to intermediate speeds(car, train, ship), to 1000 km/h (airplanes). Mobile satellite systems (e.g.INMARSAT: Horizons) which ensure up to 144 kbit/s are planned for servicing.

For IMT-2000 the frequency ranges from 1885 - 2025 MHz and from 2110 - 2200MHz should be reserved (requested by ITU).

UMTS uses in Europe the frequency ranges of 1900 - 1980 MHz, 2010 - 2025 MHzand 2110 - 2170 MHz.

The frequency ranges of 1980 - 2010 MHz and 2170 - 2200 MHz are reserved for 3GMSS.

43



Zone 4: Global

Zone 3:

Suburban / Rural

Zone 2:Urban Zone 1:

IndoorPicoCellMicro

CellMacro

CellMSS

max.

data rate144 kbit/s 384 kbit/s 2048 kbit/s144 kbit/s

UMTS - Universal Mobile Telecommunications System

1 8 5 0 1 9 0 0 1 9 5 0 2 0 0 0 2 0 5 0 2 1 0 0 2 1 5 0 2 2 0 0 2 2 5 0

cellular MSS cellular MSS

1885

2010

2110

1980

2025

2170

2200

Frequency range [MHz]

Fig. 26

44

Chapter 2

Transmission Principles



Contents

2GSM Network Structure 1 14 Duplex Transmission & Multiple Access 2 21 GSM - Fixed Network Transmission 325GSM Air Interface 4

Transmission Principles Siemens

1 GSM Network Structure


GSM Network Structure

Fig. 1

2

GSM: The Network Structure

The international GSM service area covers all countries in which there is a GSMnetwork.

Networks provisioned by an operator on a national level for public mobilecommunication are called Public Land Mobile Networks PLMN. PLMNs builttogether with public fixed networks, i.e. "conventional" PSTN (Public SwitchedTelephone Network) or ISDN (Integrated Services Digital Network) networks thetelecommunication infrastructure of a country.

A Public Land Mobile Network is divided into mobile and fixed network components.They are connected via air interfaces.

Fixed Network Components of the PLMN

The fixed network components of a GSM-PLMN consist of:

� Base Station Subsystem BSS: The BSS is the fixed network part of the PLMNradio access (Radio SubSystem RSS). It realizes the radio transmission via theradio interface. Several fixed radio station, so-called Base Stations BS are co-ordinated by one control unit.

� Network Switching Subsystem NSS: The NSS forms the interface between theradio subsystem and the public fixed networks (PSTN, ISDN, PDN). It executes allsignaling functions for setting up connections from and to mobile subscribers. It issimilar to the exchanges of fixed network communication systems, but itfurthermore fulfils important mobile communication specific functions, e.g. keepingtrack of the users / mobile stations location.

Mobile components of the PLMN

The Mobile Stations MSs are regarded as mobile part of the PLMN. The air or radiointerface represents the connection between the MS and the PLMN fixed networkcomponents BSS and NSS. The organization of the radio interface is decisive foradvantages and disadvantages of different mobile systems.

3



Mobile

terminal device

BSSBase Station

Subsystem

NSSNetwork Switching

Subsystem

control/switching of

mobile services

BSSBase Station

Subsystem

BSSBase Station

Subsystem

PLMNPublic Land Mobile Network

PSTNPublic Switched

Telephone Network

ISDNIntegrated Services

Digital Network

PDNPublic Data

Network

MSMobile

Station

Mobile

components

Fixed network

components

UmAir Interface

Fixed

network

GSM Network Structure: Concept

Fig. 2

4

Mobile Components

Mobile components are the Mobile Stations MS which transmit the users speech anddata to the PLMN. The Mobile Station MS consist of:

� ME: Mobile Equipment,

� SIM: Subscriber Identification Module,

The MS is not necessarily the termination point for the users data transmission. ATerminal Equipment TE, e.g. laptop, fax machine,... can be connected to the MS forfinal data handling.

The Mobile Station MS

An important difference between fixed network communications and mobilecommunications is the separation of equipment and subscriber identity. It is possiblefor the mobile subscriber to use various mobile terminal equipment with a personalidentity by means of the SIM card, which includes his subscriber identity. The mobilestation is defined as: MS = ME + SIM.

The SIM card is allocated and activated by the provider upon completion of thecontract. It is realized by means of a chip which contains a variety of permanent andtemporary information for the subscriber (e.g. personal telephone register) and abouthim/her. Along with the personal (secret) ID numbers (IMSI - International MobileSubscriber Identity, TMSI - Temporary Mobile Subscriber Identity) these storedinformation are for example algorithms and keys for ciphering the transmission.

The PIN (Personal Identity Number) is important for the subscriber; it must beentered by the mobile subscriber before the start of the conversation in order toprevent fraud by unauthorized intruders. As a rule, calls cannot be made without aSIM card in the ME and without the PIN being entered. Emergency calls are anexception.

5



SIMSubscriber Identification Module

MS = ME + SIM

Mobile Components

SIM card: „the heart of MS“

• Different equipments, one SIM (one bill)

• Security: PIN (exception: emergency call)• Chip with subscriber identification,

security algorithms,

personal phone book,...

Fig. 3

6

The Cellular Network

The breakthrough in mobile communications with regards to subscriber numbers andcapacity was made possible by the introduction of the cellular radio system. Thecellular communication system was tested in various countries during the 1970s.

Cellular networks of the first generation were introduced, e.g.:

� 1979 in the USA: AMPS (Advanced Mobile Phone Service)

� 1981 in Scandinavia: NMT (Nordic Mobile Telephone)

� 1985 in Germany: C-450 (Siemens)

� 1985 in Great Britain: TACS (Total Access Communications System)

The successive digital systems of the second generation, and therefore GSMsystems, are structured as cellular communication systems in the same way as theanalogue systems.

Principle of the Cellular Communication System

PLMNs operating on a national level are divided by location into servicing areas, so-called cells, in which a Base Transceiver Station BTS supplies the mobile subscribersof the area concerned. The cells represent the smallest service area in the PLMNnetwork.

A variety of cells ensures service of the total PLMN service area. The cells aretheoretically arranged in a so-called honeycomb pattern. Adaptations to thepopulation/ traffic density and the topography of the service area lead to a moreirregular pattern.

The service areas of the individual cells partially overlap. In order to avoidinterference of different subscribers in surrounding cells the cell structure isorganized according to the principle of cellular systems, frequency re-use. Thenarrow available frequency range is divided into individual frequencies (channels).Only some of these channels are used in a certain cell, the remaining channels areused in the adjacent cells. The same frequency is used again in cells which aresufficiently far apart from each other to avoid interchannel interference. This meansthat any area can be covered and thus an enormous increase in network capacitycan be achieved with a small supply of channel frequencies.

7



The Cellular

Network

Principle:• Many cells (BTS)

• Full coverage

• Partial overlap of cells

• Distribution of frequency resources

• Only a few frequencies per cell

• Frequency re-use

Solution:

cell,

radio cell

r = cell radius(cell parameter)

Principle:

~ 4 r

channels

u, v, w

channels

x,y,z

r

channels

x,y,zco-channel interference zone

= cluster area

re-use distance

for HF channel frequency

re-use distancefor

HF channel frequency

Fig. 4

8

Cluster

A certain minimum distance must be maintained between cells using the samefrequencies in order to prevent interference or at least keep it to a bare minimum.This minimum distance, the so-called frequency re-use distance, depends on theconcrete network planning and corresponds to approximately 4 times the cell radius.On this principle, the available channels can be divided e.g. into 7 parts anddistributed over the PLMN area in such a way that each cell contains one of these 7sets of frequency channels. The minimum area in which the whole range of HFchannels is used is described as a cluster. Planning a concrete network implies thatthe population/traffic density, the topography of the area to be supplied, etc. must betaken into account. This network planning is an extremely difficult process; there isspecial network planning software for this purpose.

• Frequency re-use distance: avoid inter-channel interferences

• Cluster: smallest domain within which all frequency resource is used

(GSM900: typ. 7/9 cells)

• Network planning: difficult

The Cellular Network / Principles of Network Planning

Fig. 5

9


The GSM Cell

The higher the traffic density, the smaller the cell area since a limited number of HFchannels can only cope with a limited traffic volume. This can be carried out via areduction of the cell radius or by dividing the cells into sectors.

Cell Size / Hierarchical Cellular Structures HCS

The size and shape of the cell depend on:

� The range of the MS radio contact (MS output peak power); topography (e.g.mountains, buildings, vegetation etc) and climate play a role here.

� Traffic density

The maximum radius of a cell broadcast channel is 35 km in the GSM900 system, 8km in the GSM1800 system. The possibility of setting up "extended range cells" witha radius of up to 100 km has been integrated into GSM Phase 2+ for GSM900systems. This should allow coverage of sparsely populated areas and especiallycoastal regions. The extended cell concept results in a reduced capacity.

Transmit power is limited for higher traffic densities in order to achieve a high degreeof re-use of frequencies over smaller cells: The size of clusters is inverselyproportional to the capacity of the radio system.

A Hierarchical Cell Concept (Rec. 05.22) is planned for towns, with an extremely highdensity of mobile subscribers.

� Macro-Cell: The "normal" cells are called Macro Cells. They have ranges fromapproximately one km to several (extended cell concept: 100 km).

� Micro Cell: Cells for the support of restricted areas with very high mobile userdensity, e.g. shopping malls, railway and subway stations, airport terminals. Theirradius ranges from some 100 meters to approximately 1 km.

� Pico Cell: Cells for the support of indoor applications, e.g. offices. Their rangeshould be several 10m.

Velocity dependent Handover are necessary in the Hierarchical Cellular Structures.

Cell Coverage

� Omni Cells: The BTS is equipped with omni-directional antennae and serves a360° angle.

� Sector Cells: The BTS supplies the cells with directional antennae. The cell shapeis a circular segment. Sectors of e.g. 180° or 120° are covered.

10



Cell Size and Coverage

Maximum cell size

GSM90035 km

(100 km)

8 kmGSM1800

Cell coverage

360°

180°180°

cell 1

cell 2

120°120°

cell 1

cell 2

cell 3

120°

omni cell

180°

sector cells

120°

sector cells

(extended cell)

Hierarchical Cellular Concept:

• Macro cells: min. 500 m

• Micro cells: some 100 m

• Pico cells: some 10 m

speed-dependent allocation

Fig. 6

11

Roaming / Location Registration / Handover

Roaming

A further innovation of the cellular system was so called Roaming. This means that asubscriber can move freely within the PLMN and remain reachable on a singlepersonal telephone number anywhere in this area. With GSM this concept of roamingcan be expanded to the international area (international roaming). A subscriberwhose home PLMN has a roaming agreement with other countries' GSM-PLMNs canalso be reached in these PLMNs (Visited PLMN - VPLMN) without dialing thecorresponding VPLMNs code; calls can also be made from that VPLMN. Aprerequisite is of course that subscriber’s authorization for international roaming.

Location Registration / Location Update / Location Area

The subscriber has to be located in the respective cellular network. A procedureknown as Location Registration or Location Update Procedure LUP carries outthis function. It is important that the subscriber's temporary location area is recorded /registered with this procedure when the subscriber's mobile station is switched onand checked in, to forward calls to him. The temporary Location Area LA is the areain which the MS can move freely without having to carry out a location update. As arule, the location area consists of a multiple cells and is configured by the operatoraccording to the traffic or population density.

Handover

In cellular networks, it is not necessary for the subscriber to have his call interruptedwhen changing from one cell's service area to the area of a surrounding cell, as longas the cell areas overlap. This overlapping should be guaranteed with good planning.If the MS can receive better supply from another cell than the one currently in useduring a call, the MS connection will be diverted to the relevant cell. This proceduredesigned for system quality maintenance ideally takes place without the user beingable to notice and is known as handover.

12



Roaming, Location Update

& Handover

BS

BS

Location Update:• Location Area: most precise location information

stored in the network

• Location Registration: initial registration

• Location Update: update of registration

MS

Handover

Fig. 7

13


2 Duplex Transmission & Multiple Access


Duplex Transmission

& Multiple Access

FDD TDD

UL DL

Duplex

transmission

Multiple

Access

FDMA

TDMA CDMA

Fig. 8

14

Duplex Transmission and Multiplex Procedure

In a cell for access to a network two different principles have to be co-ordinated: Theway of co-ordinating UL and DL, i.e. the Duplex Transmission, and the way ofenabling the simultaneous access of several user to the same Base Station, i.e. themultiple access principle.

Duplex Transmission: FDD & TDD

Modern cellular mobile radio systems of the first (1G) and second generation (2G)enable full duplex transmission. Simultaneous communication on both sides, i.e.(virtually) simultaneous transmission and reception is thus possible.

The transmission directions are designated as Uplink UL (MS to BTS) and DownlinkDL (BTS to MS).

There are two duplex transmission principles:

� Frequency Division Duplex FDD: Transmission and reception take place indifferent frequency ranges. The distance between the Uplink UL and Downlink DLfrequency range is designated as duplex distance.

� Time Division Duplex TDD: Transmission and reception take place in the samefrequency band. Uplink UL and Downlink DL transmission take place at differenttimes. There is fast switching between UL and DL transmission, so that the userhas the impression of simultaneous transmission and reception.

receive

transmit receive

transmit

transmit

transmitreceive

receiveMS

BS

UL ULDL DL

time t

T

frequency f

Duplex distance

UL / DLseparated by

frequency !

Same

frequency

UL / DLseparated by

time!

FDDFrequency

Division Duplex

Uplink UL

Downlink DL

Base Station BS Mobile Station MS

TDDTime

Division

Duplex

Fig. 9

15


Multiplex Access: FDMA, TDMA and CDMA

Several subscribers in one cell must be able to use the frequency range available formobile communications together. Thus there must be procedures for regulatingsimultaneous access of different subscribers without disturbances. There are threedifferent general procedures, partially in combination, which are used for co-ordinating the frequency resources:

� FDMA - Frequency Division Multiple Access

� TDMA - Time Division Multiple Access

� CDMA - Code Division Multiple Access

FDMA - Frequency Division Multiple Access

FDMA is a multiple access principle used widely in the first (analogue) generation 1Gof mobile communications. It is however also used in the second (digital) generation2G of mobile communications, usually in combination with TDMA and in the thirdgeneration 3G together with CDMA.

The available frequency reserves are divided into channels of the same bandwidthfor FDMA. A certain frequency uplink and downlink is made available to an individualsubscriber. Simultaneous calls and information transmissions of various subscribersthus take place on different frequencies. The transmitter and receiver must have acommon knowledge about the channel frequencies to use.

FDMAFrequency Division

Multiple Access

Multiplex Access

TDMATime Division

Multiple Access

CDMACode Division

Multiple Access

Co-ordination

of limited frequency resources

for different subscribers

Fig. 10

16


TDMA - Time Division Multiple Access

The allocation of the available frequency range is made with respect to time forTDMA. A frequency band is not permanently available to one mobile station; it isused by several different mobile stations. Time is therefore split into individual timeslots. The individual mobile stations are assigned the frequency range for theduration of a TDMA time slot in a periodically exclusive manner.

A certain number of subscribers can use a certain frequency range virtuallysimultaneously with TDMA. The message information of a subscriber is taken apartand transmitted piece by piece to the corresponding time slots. The informationcarrying HF transmission in an individual time slot designated as a "burst".

CDMA - Code Division Multiple Access

In CDMA systems the users of one cell are not separated by frequency or time.Different to FDMA or TDMA simultaneously they take place in the same frequencyrange. The users are separated by unique Codes. The Base Station and MobileStation must have common knowledge of the Codes used. The information of asingle user is spread up from a narrowband signal to a wideband signal using a high-frequency code (high so-called "chiprate"). This spread information is transmitted viaradio interface. After receiving the information, it is de-spread using the same code toregenerate the original information.

The Codes in principal have orthogonal properties.

frequency f

time t

power

TS 1

TS 2

TS 3

TDMA

frequency f

time t

power

1 2 3

FDMA

frequency f

time t

power

1

2

3

CDMA

Multiple

method

BS & MS share

knowledge about

FDMA

TDMA

CDMA

Frequency

Time

PN code

P

P P

Multiple Access methods

Fig. 11

17


Transmission via GSM Radio Interface Um

A combination of FDMA and TDMA is used for GSM. The GSM physical channels aredefined by a pair of frequency bands (for UL and DL) and a Time Slot TS.

FDMA in GSM

In the GSM system, a band width of 200 kHz is defined for one frequency band.These HF channel widths are perfectly suited to the demands for speechtransmission.

Allocation to (E-) GSM900, GSM-R, GSM1800 and GSM1900 is as follows:

� GSM900: (880) 890 - 915 MHz; 925 (935) - 960 MHz; 124 (174) channel pairs ;with a duplex distance of 45 MHz

� GSM-R: 876 - 880 MHz; 921 - 925 MHz; 19 channel pairs; with a duplex distanceof 45 MHz

� GSM1800:1710 - 1785 MHz; 1805 - 1880 MHz; 374 channel pairs; with a duplexdistance of 95 MHz

� GSM1900: 1850 - 1910 MHz; 1930 - 1990 MHz; common use along with otherstandards (e.g. IS-95; D-AMPS); with a duplex distance of 80 MHz

In GSM for DL the higher and for UL the lower frequency range is used in general.

Remark: In co-ordination with the frequency plan regulation, there is a 200 kHzprotective band inserted between the lower limit frequency and the first carrier ofevery sub-band, i.e. the corresponding channels are not used. This protective bandknown as the "guard band" is an accepted, virtually "unavoidable loss" for preventinginterference between different applications in the totally filled frequency range.

18



FDMA in GSMGSM900 / 1800 Frequency Allocation

C - Radio Frequency Channel (RFC)200 kHz

UPLINK (UL) DOWNLINK (DL)

Guard band

(880) 890 MHz

1710 MHz

915 MHz

1785 MHz

(925) 935 MHz

1805 MHz

960 MHz GSM900

1880 MHz GSM1800

Duplex distance 45 MHz resp. 95 MHz

25 (35) MHz

75 MHz

25 (35) MHz

75 MHz

Transmit bandof the Base Station

C

124

(174)

374

C

124'

(174')

374'

C

1

C

2

C

3

C

1'

C

2'

C

3'

Transmit bandof the Mobile Station

Fig. 12

19

TDMA in GSM

Each of the 200 kHz frequency bands is further sub-divided by TDMA into 8 so calledTime Slots TS. This produces 8 physical channels within one frequency band. InGSM a physical channel is thus defined by a determined frequency channel UplinkUL and Downlink DL and a determined time slot TS

In the GSM system, up to 8 (with half-rate transmission even 16) calls can betransmitted "simultaneously" on one frequency band.

A sequence of 8 time slots TS in one radio channel is referred to as a TDMA frame. ATDMA frame has a duration of 4.615 ms, an individual time slot a duration of approx.0.577 ms. The users data are transmitted virtually "piece by piece" on one specifictime slot every TDMA frame.

GSM:combined

FDMA/TDMA

TDMA

frame

FDMA

time

frequency200 kHz

0

1

3

2

4

5

7

6

1

0

1TS = 577 �s

1 TDMA frame =8 TS = 4.615 ms

1TS = 577 �s

1 TDMA frame =8 TS = 4.615 ms

Fig. 13

20



3 GSM - Fixed Network Transmission

PCMPulse Code

Modulation

speech band 1

speech band 3

speech band 2common line

Multi-

plexerband

3 2 1

1 0 1 1

0 0 1 1

A/D conversion

1 1 0 0

GSM - fixed network transmission


Fig. 14

21

PCM30: Transmission in GSM fixed network part

Information (conversations, data, signaling) is exclusively transmitted digitally viaPCM30 lines in the GSM-PLMNs fixed network part.

Pulse Code Modulation - PCM

Sampling values of a speech information are transmitted using binary code words(digitally) in PCM.

Due to the digital structure of the message, the PCM signals are less susceptible tointerference than analogue signals. Regenerators reconstruct the original digitalsignal at the receiving end. Analogue signals, on the other hand, can only beamplified (including noise peaks).

Amongst other things, during Pulse Code Modulation (PCM) an analogue oscillationis converted into a digital signal. A PCM signal can be transmitted alone or beembedded in a TDMA frame with other PCM signals (multiplexing).

The conversion of an analogue telephone signal into a digital signal is carried out inthree steps:

1. Band limitation: A bandpass filter restricts the incoming signal to the audiblefrequencies, i.e. to 300 to 3400 Hz.

2. Sampling: Sampling values are taken at fixed intervals from the limited telephonesignal. The sampling frequency must be greater than twice the highest frequencywithin the analogue signal (Shannon Theorem). Internationally specified: 8000 Hz.

3. 8-bit coding: Every amplitude value of the sampled (Pulse Amplitude Modulated -PAM) signal is transformed into an 8-bit word. The 8-bit word enables the analoguesignal to be represented in 256 quantization intervals.

Since the transmission of an 8-bit word requires only a portion of the sampling

interval (125 �s) of the analogue signal, the 8-bit information is temporallymultiplexed (TDMA-procedure). 8 bits are transmitted in each time slot.

Using PCM30 transmission systems, a total of 30 digital user values can betransmitted in the time frame of the sampling period of an analogue value, i.e. in 125

�s.

22



1. Band limitation

(300-3400 Hz)

2. Sampling (8000 Hz)

3. 8-bit coding

Generation of a PCM Signal

transmission of the coded

sample value of signal 1

coded sample value

signal 2

time slot

0 1 0 0 1 1 0 1

signal 1

Fig. 15

23

PCM30

PCM30 transmission systems use digital transmission lines or radio relay. A PCM30frame consists of 32 time multiplexed time slots.

The 32 time slots can contain pulse code modulated message information (speech,data) or signaling information in the form of 8-bit words.

The total bit rate of a PCM30 line is 2048 kbit/s

� Time slot 0: alternately frame identification word and service word (alarms)

� Time slots 1-15 and 17-31: calls or data

� Time slot 16: signaling channel

The pulse frames are transmitted in a direct sequence.

PCM30: TDMA Principle

telephone channels 1 - 15 telephone channels 17 - 31

frame alignment/

service word channelsignaling channel

time

slot

PCM30PCM30

pulse frame pulse frame pulse frame

Fig. 16

24



4 GSM Air Interface

GSM Air Interface

Advantage:

mobility

Single cell systems Cellular mobile communication systems

Limits:

1st generation 2nd generation incl. satellite roaming

cell national GSM service area unlimited

GSM (Ph1/2) (GSM Ph2+)


Fig. 17

25

Radio Interface: Advantages, Problems and Solutions

The air or radio interface, i.e. the connection between the MS and fixed networkcomponents, represents the fundamental difference to a fixed networktelecommunication system. The radio interface has its specific advantages, but alsoshows problems and disadvantages inherent to mobile communications.

Advantage: Mobility

The main advantage of mobile communications is the unrestricted mobility which canbe achieved only via a radio interface. Mobility was extremely restricted, especially inthe early years of mobile communications (one-cell systems). Mobility only reachedas far as the radio coverage between the MS and the transmission/receivinginstallations would allow. These limits were stretched significantly by cellular mobilecommunication networks of the first generation (since the early 1980s). Nationalborders and the degree of area coverage of a PLMN within a country formed theborders. In the GSM system, national borders no longer represented restrictions tomobility owing to “inter-national roaming”. It is still the case that nation-wideconnectivity is only offered around urban areas and along main traffic routes in largeareas of central Europe. Unlimited world-wide mobility is possible in co-operationbetween GSM and MSS such as Iridium, Globalstar and ICO.

Problems & Solutions on the Radio Interface

� Cost Aspect: Problem - The need to built up a new network architecture withthousands of BTS. But: Compared with the costs for a fixed network ISDN / PSTNinfrastructure, a GSM PLMN is comparable cheap, because there is no need formillions of lines into every private household.

� Capacity: The capacity of transmission via radio interface is a great problem inmobile communications. Optimized usage of radio resources reducing the cellsizes, introducing sector cells and introducing the Hierarchical Cellular Structureswith Macro, Micro and Pico Cells solves this problem.

� Data Rate: GSM (Phase 1/2) offers a maximum 9.6 kbit/s, compared to the 64kbit/s of ISDN. Introduction of HSCSD, GPRS and EDGE enhances the GSM datarates significantly.

� Security Aspect: The radio interface can be intercepted with comparatively littletechnical expenditure. 1G could be intercepted without any problem, while thedigital transmission of the second generation offers protective measures againstinterception; the transmission is coded.

� Health Aspect: The mobile radio frequencies lie near the resonance frequency ofwater (2.45 GHz). In order to keep thermal exposure to the mobile radio user aslow as possible there are maximum power limitations for mobile phones, 2 W forGSM900 and 1 W for GSM1800.

26



The Air Interface Um:Problems of radio transmission and possible solutions

Cost Aspect:

Capacity:

Data Transmission Rate:

Security Aspect:

Health Aspect:

Construction of mobile

communication network

cheaper than terrestrial network

GSM900 / E-GSM: 124 / 174 frequency bands

GSM1800: 374 frequency bands

increasing subscriber numbers, data transmission

�� Resource optimization / protection !!!

GSM Ph1/2: � 9.6 kbit/s

Ph2+: HSCSD, GPRS, EDGE > 100 kbit/s

Eavesdropping easy!

GSM offers encryption

H2O resonance frequency (2.45 GHz)

Thermal load

� Pmax

= 2 / 1 W (GSM900/1800)

Fig. 18

27

Problems of Physical Transmission

� Screening: If there are hindrances between transmitter and receiver, the signalswill weaken. A connection can thus become problematic or impossible. In GSMthere is therefore the possibility of regulation of the transmitting power (PowerControl - PC) from mobile and base stations over several orders of magnitude.

� Multipath Propagation: Multipath propagation through reflection and dispersionof radio waves leads to phase-shifted reception of signals of different paths. Theinterference can distort, amplify or erase the signal. An attempt to compensate fornegative effects of multipath propagation is given by power control, frequencyhopping, two antenna receivers for the base station (antenna diversity) andredundancy of the transmitted information.

� Distance MS - BTS: The distance between MS and BTS has proved to beproblematic in several ways. The receive power sinks with increasing distancebetween transmitter and receiver theoretically with the square of the distance.Various physical effects such as atmospheric attenuation (weather-dependent)reduce the receive power even more. This attenuation depends on the frequencyand increases with increasing frequency in mobile radio relevant frequencyranges. The distance furthermore causes a reception de-lay, which may lead tointerference between neighboring time slots in TDMA. GSM responds to this delayby means of a regulation of the transmission time (Timing Advance TA). GSM900cells (GSM Phase 1/2) are limited to maximum 35 km, GSM1800 cells tomaximum 8 km radius as a result of the distance-related problems. There is thepossibility in GSM Phase 2+ to realize "Extended Range Cells" with a maximumradius of 100 km for GSM900.

� MS Speed: Moving mobile stations can cause transmission distortions due toDoppler effect. A compensation for this effect up to a maximum speed of 250 km/h(130 km/h), for GSM-R a more powerful compensation for speeds of up to 450km/h was deloped.

� Interference with external systems: The receive quality can also be disturbed byelectromagnetic waves from outside systems (e.g. car ignition, generators, PCs).A compensation is being tried out by means of the mechanisms described undermultipath propagation.

28



Radio Transmission: Physical Disturbances

Mobility

• Screening

• Multipath propagation

• Distance MS-BS

• MS speed

• External system interferencetransmitted signal

received

signals

signal to

antenna

Digital systems offer manyerror recognition and

correction mechanisms( � redundancy)

�� signal attenuation (Power Control PC)�� interference (PC, f-hopping, diversity, regeneration)�� power loss (f-dep.); delay (PC, TA, cell size)�� Doppler effect (corrections)�� quality loss (PC, f-hopping, regeneration)

Fig. 19

29

Frequency Resources: Optimized Utilization

In order to be able to keep up with the increasing demands on mobilecommunications despite the limited resources of the radio interface differentapproaches are being pursued.

� Additional Frequency Ranges: The simplest way to cope with the growingdemand for mobile communications is to expand the available frequency range.This approach was pursued with E-GSM and GSM1800. Any further futureexpansion would be problematic as other frequency ranges are already reservedfor other applications.

� Speech Compression: Speech compression in GSM allows a reduction of voiceinformation from 64 kbit/s to 13 kbit/s in the so-called Full Rate FR speech and to5.6 kbit/s with the Half Rate HR speech. HR speech thus leads to a considerableincrease in capacity. Central aspects of HR speech are described in the GSM Rec.06.02, 06.20 - 22, 06.41 and 06.42.

� Cell Size Reduction/Coverage: The most important measure for increasing thecapacity of GSM networks lies in a reduction of the cell size. The resources of aradio cell are available to a small geographical area through the reduction of thecell radius or through the limitation of the cell coverage (sector cell). By doing so,the density of mobile communication subscribers and consequently the systemcapacity can be considerably increased. By halving the cell radius, its capacity isincreased by a factor of four. Nevertheless the size of a (normal = macro) cell cannot be reduced indiscriminately. Hierarchical Cell Concepts (Rec. 05.22) withmacro, micro and pico cells are significantly enhancing efficiency.

� OACSU (Off Air Call Set Up): Traffic channels are allocated only after a success-full call setup, that is after the called subscriber (delayed allocation). The OACSUprocedure thus serves to improve the frequency efficiency; it can be used foroverload handling.

� Tariffs: Introduction of day- & night time tariffs can help to level down peak loads.

� Discontinuous Transmission DTX: For a conversation, this will mean that justspeech phases are transmitted. Background noise, or so called comfort noise istransmitted with a greatly reduced bitrate (500 bit/s instead of 13 kbit/s as withspeech phase) in phases in which a subscriber is silent. The other subscribershould thus not worry that connection has been broken off. In order to makediscontinuous transmission possible, the presence of "useful" information fortransmission must be determined by means of Voice Activity Detection VAD. DTXaspects are included in GSM-Rec.06.31 and 06.41, VAD aspects in Rec. 06.32and 06.42.

30



Frequency Resources: Expansion / Optimized Utilization

GSM900: 2 x 25 MHz

• Extension of frequency range:

E-GSM: 2 x 35 MHz

GSM1800 2 x 75 MHz+��

Fixed network: 64 kbit/s

• Speech compression:

��FR:

13 kbit/s

Digital speech information

HR:5.6

kbit/s

Half Ratespeech

Full Ratespeech

• Cell size

reduction:

��(Radius reduction

and sectorization)

35 / 8 km 500 m

omnicell

180° / 120°

sector cell

• OACSU (Off Air Call Set Up)

• Time Balance / Tariffs

• DTX (Discontinuous Transmission) / VAD (Voice Activity Detection)

Fig. 20

31

Advantages of Digital Transmission

Digital transmission has many advantages over analog transmission:

� Network Capacity: The capacity of mobile communication networks can beconsiderably increased by the possibility of compressing digitalized speechinformation. The disadvantage of speech compression is a loss of information(reduction of speech quality).

� Service Offer: Digital data transmission simplifies the transmission of signalinginformation. This makes the introduction of a wide, quickly growing range ofservices possible in GSM beyond pure speech or data transmission.

� Cost Aspect: Digital equipment is less expensive to manufacture owing to betterpossibilities for use in highly integrated microelectronics. Purchase costs as wellas operation and maintenance costs are thus less expensive and have allowedGSM's breakthrough onto the mass market.

� Miniaturization: Microelectronics used for digital information transmission allowsa relatively simple reduction of the hardware (in comparison to analogtransmission), especially of the mobile stations. Mobile phones have been usedwith GSM since the start; their weight has been reduced from over 500 g to some50g within a couple of years.

� Security Aspect: Digital information can be ciphered much more easily thananalog information. Transmission via radio interface is protected from fraud andunauthorized interception in GSM by the ciphering the digital user data (speech,data) and signaling data.

ENCRYPTION

MODULE

Input data

(plain text)

Output data

(coded text)

Code

sequence

Advantages of Digital Information Transmission

• Network capacity � speech compression

• Service offer � signaling

• Cost aspect � manufacture, operation, maintenance

• Miniaturization � microelectronics

• Security aspect � easily coded

• Transmission quality � regenerability

Fig. 21

32


� Transmission Quality: Signal transmission via radio interface leads to consider-able distortions and weakening of the transmitted signals. Digital signals arefundamentally less susceptible to interference than analog signals and are bettersuited to regeneration. Analog speech connections become increasingly worsewith increasing distance from the transmitter until they eventually disconnect.Digital transmissions on the other hand maintain a constant good quality over along distance and then disconnect almost suddenly.

S / N

signal

quality

distance to transmitter r

analog signal

digital signal

Quality of Digital & Analog Signal Transmission

Fig. 22

33


Reliable Transmission via Um: Channel Coding

Various measures are taken in GSM to protect transmissions via radio interface frominterference, distortions and loss of information. These measures are taken by meansof channel coding.

The transmission is protected in such a way that a certain number of transmissionerrors can be corrected by the error correction procedure, the so-called ForwardError Correction (FEC). By means of FEC the Bit Error Rates (BER) of the radiointerface transmission are reduced to a rate of 10-5 to 10-6 from an unacceptablevalue of 10-3 to 10-1. Redundancy is added to the information to be transmitted inorder to al-low recognition and correction of transmission errors.

Channel coding of information on the transmit side comprises three steps:

1. Adding of parity check bits and fill bits

2. Error protection (redundancy) with convolutional coding

3. Spreading by time: interleaving

The same steps are carried out in reverse order at the receiving side.

The added parity check bits serve to recognize incorrigible errors on the receivingside. The parity check bits are of special use in speech transmission. If incorrigibleerrors are indicated, the corresponding speech information is rejected and an attemptis made to interpolate the information from the preceding speech information.

Convolutional coding serves to create redundancy. The original information (speech,data, signaling) is coded along with the parity bits. Important information runs throughmathematical algorithms, where redundancy is added and the arrangement of theinformation is changed.

Interleaving serves to temporally spread information. Information is collected up to adetermined number of bits and is spread by time. The interweaving of the redundantinformation has the effect that information loss due to frequent short disturbances canbe compensated by means of temporal spreading of the information.

34



Reliable Transmission via Um:

Channel Coding

Addition of:

parity

and filler

bits

transmission side

Convo-

lutional

coding

redundancy

Inter-

leaving

temporalspreading

Parity

check

Convo-

lutional

decoding

De-inter-

leaving

reception side

Um

Fig. 23

35

Speech Coding: FR, HR and EFR

Speech transmission is of central importance in GSM. Speech information is handledespecially by the radio interface for secure and resource-preserving transmission.Speech information is compressed and then redundancy is added (channel coding).There are three different speech codecs available in GSM for compression of speechinformation: the Full Rate (FR) Speech Codec was specified for GSM Phase 1, i.e.from the start, in Phase 2 the Half Rate (HR) Speech Codec and in Phase2+ theEnhanced Full Rate (EFR) Speech Codec were added.

Full Rate FR and Enhanced Full Rate EFR Speech Codecs compress speechinformation from 64 kbit/s - used in digital line connected telephone networks such asISDN - to 13 kbit/s respectively 12.2 kbit/s. So 13 kbit/s / 12.2 kbit/s are the net datarate for speech transmission via the radio interface. The gross data rate after addingredundancy in channel coding is 22.8 kbit/s with FR and EFR.

� Half Rate HR Speech Codec compresses speech information from 64 kbit/s to 5.6kbit/s. The gross data rate after adding redundancy is 11.4 kbit/s. The connectionsof two Half Rate speech using subscribers can be realized in one physical channeltogether, with a gross data rate of 22.8 kbit/s.

Models for speech generation are generally used for speech coding. Periodically re-turning elements of speech are identified as phonemata; redundancy is removedfrom the speech information. Even the attributes of hearing, especially the spectralcovering effect, are taken into account in different ways.

More efficient speech recognition mechanisms are of use for the HR introduced inGSM Phase 2 and EFR introduced in Phase 2+. The HR codec delivers a somewhatlower speech quality in comparison to the FR codec if transmission is undisturbed. Itis more robust against radio specific disturbances owing to the relatively strong errorprotection. The EFR codec offers a significant increase in quality in comparison to theFR codec. It sounds more natural and "smoother" according to subjective test results.

36



Speech Coding: FR, HR, EFR

Speech coding � models of speech and hearing• Removal of redundant information (periodic)

• Transmission of central speech information

• Reduction of speech information: 64 kbit/s � 13 / 5.6 kbit/s (net data rate)

Full Rate (FR) CodecGSM Ph1;

13 kbit/s

Redundancy (channel coding)

9.8 kbit/s

Enhanced Full Rate (EFR) CodecGSM Ph2+;

12.2 kbit/s

Redundancy (channel coding)

10.6 kbit/s

Gross data rate via Um: 22.8 kbit/s

Half Rate (HR)Codec; GSM Ph2;

5.6 kbit/s

Redundancy

5.8 kbit/s

Gross data rate via Um: 11.4 kbit/s

HR & EFR: improved, acoustically optimized

speech coding

HR, FR almost the

same quality

Fig. 24

37

Chapter 3

GSM PLMN

GSM PLMN

GSM PLMN

Contents

2Overview1 7 Network Elements 2

GSM PLMN Siemens

1 Overview

PLMN Public Land Mobile Network

PSTNPublic Switched

Telephone Network


Digital Network

PDNPublic Data

Network

MSMobile

Station

fixed

network

GSM-PLMN

BSSBase Station

Subsystem


Subsystem

OSSOperation SubSystem

RSSRadio

SubSystem

Overview

Fig. 1

2

Siemens GSM PLMN

GSM PLMN: Subsystems

A GSM-PLMN is subdivided into the following subsystems:

� Radio SubSystem RSS

� Network Switching Subsystem NSS

� Operation SubSystem OSS

Network Elements

The subsystems functions are grouped into functional units or network elements.Functional units may be realized either as standalone Hardware HW units orassociated with other GSM functional units in one HW unit.

The Radio SubSystem RSS consists of the Mobile Stations MS and the BaseStation Subsystem BSS, which is composed of the following functional units:

� Base Station Controller BSC

� Base Transceiver Station BTS

� Transcoding and Rate Adaption Unit TRAU

The Network Switching Subsystem NSS (Phase ½) consists of the followingfunctional units:

� Mobile services Switching Center MSC

� Visitor Location Register VLR

� Home Location Register HLR

� Authentication Center AC

� Equipment Identity Register EIR.

The Operation SubSystem OSS consists of Operation & Maintenance CentersOMC; in the Siemens solution:

� Operation & Maintenance Center for the Base Station Subsystem OMC-B

� Operation & Maintenance Center for the Switching Subsystem OMC-S.

3

GSM PLMN Siemens

GSM PLMN Siemens

OMC- B OMC- S

MSC

HLR VLR

EIRAC

BSC

BTST

R

A

U

Mobile

Station

MS

Radio

SubSystem

RSS =

Base Station

Subsystem

BSS

Network

Switching

Subsystem

NSS

+

other

networks

Operation SubSystem OSS

PSTN

ISDN

Data

NetworksMS =

ME + SIM

GSM-PLMN

Fig. 2

4

Siemens GSM PLMN

Interfaces

The individual network elements are connected to each other for user data and/orsignaling transfer. Some of the interfaces are specified by ETSI as open interfaces,allowing to connect equipment of different network manufacturer. Others are notspecified or "weakly" specified, so that only proprietary solutions are possible.

The following GSM Phase 1/2 interfaces are open interfaces:

� Um: MS - BSS (Air interface)

� A: MSC - BSS (BSC)

� B: MSC - VLR

� C: MSC - HLR

� D: HLR - VLR

� E: MSC - MSC

� F: MSC - EIR

� G: VLR - VLR.

The following interfaces are proprietary solutions:

� Asub: BSC - TRAU

� Abis: BSC - BTS

� T: BSC, BTS, TRAU - Local Maintenance Terminal LMT

� O: BSC - OMC-B

� HLR - AC (no name)

5

GSM PLMN Siemens

GSM PLMN Siemens

T

MS BTS

BSC

TRAU

VLR

AC

other networks

MSC/xxx interworking interface

LMT

LMT

LMT

OMC - B

Um Abis A

sub

C

B

F G

E DT T

O

A

GSM (Phase 1/2)

Interfaces

not specified

EIR VLR

HLRMSC

MSC

Fig. 3

6

GSM PLMN Siemens

2 Network Elements

GSM-PLMN


PSTNPublic Switched

Telephone Network


Digital Network

PDNPublic Data

Network

MSMobile

Station

fixed

network

BSSBase Station

Subsystem


Subsystem


RSSRadio

SubSystem

Network Elements

Fig. 4

7

Siemens GSM PLMN


The Mobile Stations represent the mobile network components. They consist of theMobile Equipment ME and the Subscriber Identity Module SIM: MS = ME + SIM

The SIM card

The SIM consists of a microchip, which uses either a check card or a plate made of asynthetic material as a carrier. Without a SIM card, the use of an MS is normally notpossible. An exception is the emergency call, which should always be possible with afunctioning ME. The SIM card carries the subscriber-related information and codes,so that a GSM subscriber with a SIM card can use different ME. The main task of theSIM is the storage of data: permanent and temporary administrative data as well asdata concerning security. Personal telephone lists may be stored and using the SIMtoolkit with enhanced memory space, it is possible to enable applications such asMobile Banking, etc.

Important stored codes are e.g.:

� Personal Identity Number - PIN

� PIN Unblocking Key - PUK

� Mobile Station ISDN number - MSISDN

� International Mobile Subscriber Identity - IMSI

� Temporary Mobile Subscriber Identity - TMSI

Important data relating to security are, e.g.:

� the individual key - Ki

� the cipher key - Kc

� the algorithms for authorization and ciphering (A3, A8).

8

GSM PLMN Siemens

GSM PLMN Siemens

ME:Mobile Equipment

•Hardware & Software for radio transmission•Cipher algorithm

SIM cardSubscriber Identity Module:


MS = ME + SIM

� Subscriber license

� Personal Identities

� (e.g.MSISDN, IMSI, TMSI, PIN,...)

� Subscriber key (Ki, Kc)

� Algorithms (A3, A8)

� Personal phone book

� SIM toolkits,...

MSISDN: Mobile Subscriber ISDN no.

IMSI: International Mobile Subscriber Identity

TMSI: Temporary Mobile Subscriber Identity

PIN: Personal Identity Number

Ki: individual key

Kc: cipher key

Fig. 5

9

Siemens GSM PLMN

The Mobile Equipment ME

The Mobile Equipment ME unites the tasks of many functional elements of the fixedGSM-PLMN network.

By using the data of the SIM card, the speech is digitalized, compressed, securedagainst loss of data (redundancy + interleaving), encrypted to prevent interceptionand modulated onto the Radio Frequency (RF) created by the mobile station. Directlyafter, the signal is amplified and transmitted.

In the opposite direction, the process runs inversely, beginning with the reception ofthe radio frequency (RF).

The MS represents the counterpart to BSC, MSC, HLR, VLR and EIR as regardssignaling. As a whole, ME and SIM cards are almost a complete GSM system asregards their functionality.

GSM Mobile Station

speechconversion

block diagram

Subscriber Identity Module SIM

Mobile Equipment ME

• securing• interleaving• burst block formation

ciphering

• HF generation• modulation• amplification

reverse speech conversion

• security check• de-interleaving• reformation

de-ciphering

• filtering• amplification• de-modulation

�

• Radio transmission counterpart to

BTS, BSC & TRAU

• Signaling counterpart to

BSC, MSC, HLR/AC, VLR & EIR

Fig. 6

10

GSM PLMN Siemens

Siemens GSM PLMN

The Base Station Subsystem BSS

The BSS consists of the following network elements:

� BSC: Base Station Controller

� BTS: Base Transceiver Station

� TRAU: Transcoding and Rate Adaption Unit

� LMT: Local Maintenance Terminal

The BSS architecture shall be selected to achieve maximum flexibility with regards tothe various operator requirements. All BSS components can be installed in the samegeographical location or in different locations where the transmission paths can beused via public networks. The ability of the BSC to manage several BTSs in differentcell locations enables optimal adaptability to the traffic requirements in urban andrural areas.

In terms of function, the main task of the BSC is the handling of the call connections(switching), sampling of operational/maintenance information of all BSS (BSC, BTSsand TRAUs), as well as their transfer to OMC-B. The BTS handles the radio specificaspects.

BSCTRAU

LMT

BTS

BTS

BTS

TRAU

Base Station Subsystem BSS

Architecture

MSC

OMC-B

Fig. 7

11

GSM PLMN Siemens

Siemens GSM PLMN

Base Station Controller BSC

The Base Station Controller BSC is, as the controlling element, the heart and centerelement of the BSS.

BSC Location: between the interfaces Asub and Abis

BSC Functions:

� switching of the user traffic between individual TRAUs and BTSs

� control and monitoring of the connected TRAUs and BTSs

� sampling of operation and maintenance information of BSC, TRAUs and BTSs aswell as transfer to OMC-B

� evaluation of signaling information from MSC via TRAU and MS via BTS

� Radio Resource Management for all connected BTSs

� storage of the BSS configuration

� back-up storage of the total BSS Software for fast system restart

TRAU

TRAU

TRAUBSC

BTS

•

•

•

BTS

BTS

Base Station Controller BSC

•

•

•

• BSS control

• Switched between TRAU � BTS

• Radio Resource Management

• Collecting error messages in BSS

• Contact to OMC-B

• Database storage, SW of BSS

• BSS control

• Switched between TRAU � BTS

• Radio Resource Management

• Collecting error messages in BSS

• Contact to OMC-B

• Database storage, SW of BSS

OMC- B

Asub

Abis

Fig. 8

12

GSM PLMN Siemens

Siemens GSM PLMN

Base Transceiver Station BTS

A BTS is the module which operates an individual cell and realizes the radiointerface. A BTS encompasses all applications concerning radio transmission(sending, receiving), as well as the air interface specific signal processing. The BTSis connected via the Abis interface with the BSC and via Um interface to the MSs.

Functions:

� Channel coding: To protect the transmission, incoming information is provided withparity check bits and redundancy (convolutional coding) and spread in time overseveral HF bursts (interleaving).

� Ciphering: After channel coding, the transmission of message information and thesubscriber data is coded to prevent illegal interception.

� Burst block formation: The information is organized in blocks of a particular length(burst blocks). A so-called training sequence is added for synchronization andanalysis of transmission quality.

� Modulation: The carrier frequency is created in the 900/1800/1900 MHz range andthe information is modulated upon this carrier.

� Power Control PC: Control of the power level of the BTS and MS.

� Timing Advance TA: Calculation of the distance of the MSs from the BTS; the MSsare informed of necessary transmission advance.

� Frequency Hopping: a feature which enhances the reliability of information transfer

� Synchronization: Providing of mobile stations with frequency and timesynchronization information.

13

GSM PLMN Siemens

GSM PLMN Siemens

Um

parity

bits

convolutional

coding

inter-

leaving

channel coding

burst blocks

formation

burst

multiplexing

transmitHF generation modulation

modulation

user and signaling

information

Abis

receive

max. 16 carrier/cell

• Frequency hopping

• Synchronization

(time and frequency)

• Monitoring & optimization

of transmission quality

• Power Control PC

• Timing Advance TA

ciphering

Base Transceiver Station

BTS

+

Fig. 9

14

Siemens GSM PLMN

Transcoding and Rate Adaptation Unit TRAU

The TRAU is used for speech compression (Transcoding) and adaptation of data tothe requirements of the air interface (Rate Adaptation). It lies between A and Asubinterface.

Functions:

� Transcoding TC defines speech compression: compresses / decompresses theincoming speech data from 64 kbit/s to 13 kbit/s, 12.2 or 5.6 kbit/s (embedded in16 or 8 kbit/s channels).

� Rate Adaptation RA filters out the useful data (0.3 – 9.6 kbit/s in Phase 1/2)coming from the MSC (64 kbit/s) signal and forms a 16 kbit/s signal toward theBSC

� The user data are sub-multiplexed into 16 kbit/s subslots on the Asub interface

Remarks:

� TC and RA are implemented as algorithms in the same hardware unit as theTRAU (Siemens solution).

� The TRAU is logically allocated to the BSC. Consequently, it belongs to the BaseStation Subsystem (BSS), but is generally installed at the MSC node in order tokeep line costs to a minimum.

� In contrast to user information signaling information passes the TRAUtransparently.

� The users information (data / speech) is embedded into 16 kbit/s channels. Theadditional space is filled with proprietary inband-signaling (i.e. information, whichare directly exchanged between BTS and TRAU)

15

GSM PLMN Siemens

GSM PLMN Siemens

TRAU

64 kbit/s64 6464

64 kbit/s64 6464

64 kbit/s64 6464

64 kbit/s64 6464

16

16

16

16

B

S

C

M

S

C64 kbit/s64 6464

16161616

submultiplexer

• speech compression: 64kbit/s � 13 or 5.6 kbit/s + inband signaling

• data transmission: "64 kbit/s" � 0.3 - 9.6 kbit/s + inband signaling

• signaling: transparent

• speech compression: 64kbit/s � 13 or 5.6 kbit/s + inband signaling

• data transmission: "64 kbit/s" � 0.3 - 9.6 kbit/s + inband signaling

• signaling: transparent

TRAUTranscoding & Rate Adaptation Unit

Asub

A

Fig. 10

16

Siemens GSM PLMN

The Network Switching Subsystem NSS

The NSS comprises the following functional elements:

� MSC: Mobile services Switching Center

� VLR: Visitor Location Register

� HLR: Home Location Register

� AC: Authentication Center

� EIR: Equipment Identity Register

Mobile services Switching Center MSC

The MSC is concerned with the central tasks of the NSS and covers the serviceareas of several BSSs. These tasks can be compared to those of an exchange in afixed network. These tasks are supplemented by mobile specific tasks of the sub-scriber administration. The MSC handles connection tasks in the PLMN, i.e. set-up ofcircuit connections to the BSS, between each other and other networks (e.g. PSTN).The MSC visited by a customer is described as a VMSC (Visited MSC). A MSC,which represents an interface to other networks, is called GMSC (Gateway MSC).

MSCs connect the other networks with the Base Station Subsystem BSS, as well asthe other NSS units with the BSS via the signaling highways.

The MSC is a stored program controlled switching system for national andinternational GSM-PLMN applications. The MSC is a switching center that carries outall switching for the mobile stations which are actually located in the MSC area.

Other functional units of the NSS (e.g. HLR, VLR, AC,...) can be associated to theMSC.

17

GSM PLMN Siemens

GSM PLMN Siemens

other

networksMSC

Mobile services

Switching Center

other

MSC/VLRs

VLRVisitor Location

Register

EIREquipment Identity

Register

HLRHome Location

Register

ACAuthentication Center

NSSNetwork &

Switching

Subsystem

Fig. 11

18

Siemens GSM PLMN

Overview of call processing functions

The MSC follows the functions of a fixed network exchange as regards itsfunctionality. Consequently, varied proven call handling functions form the basis formobile specific supplementary services.

� Switching of user connections

� Routing functionality (path selection)

� Signaling with other MSCs and external network exchanges

� Evaluation of available signaling information for destination routing:

� Digit translation

� Legal interception

� Coping with abnormal signaling conditions, e.g. loss of signaling information

� Supplementary Service support

� Processing of transmission path attributes, e.g. echo compensation

� Call supervision

� Overload protection

� Control of priority calls, e.g. emergency call

� Charging

� Traffic measurement and traffic observation

� Support of maintenance and administration functions, e.g. connection cut off, trunktest and measurement

19

GSM PLMN Siemens

GSM PLMN Siemens

MSC

Mobile services

Switching Center

call processing functions(similar to fixed network exchange)

mobile communication -

specific functions

• NSS “heart & center”

• Nodes between NSS registers, BSS,

other MSCs and external networks

• Serves several BSS (BSC)

• Set-up & switching of user traffic & signaling

• Always associated with VLR

• Association with HLR/AC and EIR possible

• Gateway MSC: Gateway to external networks

• Visited MSC: MSC serving certain MS

• NSS “heart & center”

• Nodes between NSS registers, BSS,

other MSCs and external networks

• Serves several BSS (BSC)

• Set-up & switching of user traffic & signaling

• Always associated with VLR

• Association with HLR/AC and EIR possible

• Gateway MSC: Gateway to external networks

• Visited MSC: MSC serving certain MS

Fig. 12

20

Siemens GSM PLMN

Mobile specific functions

Additional to normal fixed network exchanges, the MSC has many mobile specificfunctions due to the users mobility.

Mobile specific functions are for example:

� Signaling with BSC, MS & NSS databases (EIR, HLR, VLR)

� Processing of mobile-specific services

� Mobility Management, e.g. Paging, Inter-MSC Handover, Location Update,...

� Overload handling, e.g. OACSU

� Interworking Function for data services

� Mobile specific Announcements

� ...

MSC

Mobile services

Switching Center

call processing functions(similar to fixed network exchange)

• Set-up of signaling / user connections

• Signaling evaluation � destination determination• Connection path selection

• Processing of abnormal signaling information• Supplementary Service support

• Call monitoring

• Traffic monitoring & measurement

• Overload protection

• Billing

• Priority control (e.g. emergency call)

• Support of O&M functions

mobile specific functions

• Signaling with BSC, MS & NSS databases

• Processing of mobile-specific services

• Mobility Management, e.g. Paging, Inter-MSC Handover, Location Update,...

• Overload handling, e.g. OACSU

• Interworking Function for data services

• Mobile specific announcements

Fig. 13

21

GSM PLMN Siemens

Siemens GSM PLMN

Visitor Location Register VLR

The Visitor Location Register VLR is responsible to aid the MSC with information onthe subscriber, which are temporarily in the MSC service area. Therefor, in praxis it isalways associated with an MSC.

The VLR request the subscriber data of user with activated MS on the MSC servicearea from the HLR and stores them temporarily. Temporarily means as long as thesubscriber is not registered in a new MSC/VLR, even if he deactivated the MS.

Additional to the semipermanent subscriber data received from the HLR the VLRstores temporary data, e.g. information on the subscribers current location (theLocation Area), the state of activation (Attached / Detached),...

Furthermore, the VLR is responsible for the initiation of security functions, e.g. theAuthentication procedure, the start of ciphering and the TMSI re-allocation.

Examples of subscriber data in the VLR:

� MSISDN: Mobile Subscriber ISDN number

� IMSI: International Mobile Subscriber Identity

� TMSI: Temporary Mobile Subscriber Identity

� HON: Handover Number

� LMSI: Local Mobile Subscriber Identity

� MSRN: Mobile Station Roaming Number

� Triples (Authorization parameters )

� ....

22

GSM PLMN Siemens

GSM PLMN Siemens

MSC

Mobile services

Switching Center

VLRVisitor Location Register

Tasks:

• Subscriber management in MSC area

• Associated with MSC

• Authentication co-ordination

• commands start of ciphering

Subscriber data:• Subscriber data from HLR (MSISDN, IMSI, services (BS, TS, SS), service restrictions,..) • Temporary subscriber information (LMSI, TMSI, LAI,

IMSI attach/detach, MSRN, HON, triples,...)

Entries valid until re-registration in another VLR!

Fig. 14

23

Siemens GSM PLMN

Home Location Register HLR

The Home Location Register HLR is the main data base of the mobile subscriber.The subscription of a user / his subscription data is stored in one HLR only. Theremay be one or more HLRs in a GSM PLMN.

The HLR is always associated with an Authentication Center AC.

The HLR performs the following important tasks:

� It sends all necessary data to the VLR.

� It supports the call setup in case of Mobile Terminating Calls MTC by sendingrouting information to the Gateway MSC (Interrogation).

� It transmits the Triples from AC to VLR on request

An HLR contains different semi-permanent mobile subscriber data, e.g.:


� MSISDN: Mobile Station International ISDN number

� Bearer Services BS

� Tele Services TS

� Supplementary Services SS

� Restrictions

An HLR contains different temporary information of the mobile subscriber, e.g.:

� VLR address

� Local Mobile Subscriber Identity LMSI

� Mobile Station Roaming Number MSRN

� SMS flags

24

GSM PLMN Siemens

GSM PLMN Siemens

HLRHome Location Register

Tasks:

• Central storage/management of subscriber data

• Delivery of data to VLR

• Routing information at MTC

• Associated with AC

Subscriber data:

• Semipermanent data: MSISDN, IMSI,

services (BS, TS & SS), service restrictions,...

• Temporary subscriber information: VLR address,

LMSI, MSRN, SMS flags,...

ACAuthentication Center

Tasks:

• Security data storage (Ki)

• Generation of triples (VLR request)

• Associated with HLR

Data / algorithms:

• Ki, IMSI, A3, A8

Fig. 15

25

Siemens GSM PLMN

Authentication Center AC

An Authentication Center AC contains all necessary means, keys and algorithms forthe creation of security related authorization parameters, the so-called Triples. TheTriples are created on VLR request and delivered via HLR to the VLR. An AC isalways associated with an HLR.

Central information contained in the AC are:


� Ki: Individual Key (top secret mobile subscriber identity)

� Algorithms for authentication and encryption: A3, A8.

Equipment Identity Register EIR

The Equipment Identity Register EIR contains the Mobile Equipment identity: theInternational Mobile Equipment Identity IMEI. An IMEI clearly identifies a uniqueMobile Equipment ME and contains information about the place of manufacture,device type and the serial number of the equipment.

EIR are an optional feature in GSM. They have been defined by ETSI to enable theftprophylaxis. They carry out equipment identification functions: monitoring of stolen ornot allowed MEs.

There are three validity lists in EIRs: "white", "gray" and "black" lists for valid, to beobserved and to be blocked equipment.

A Common EIR (CEIR) in Dublin (Ireland) enables the world-wide identification ofstolen mobile equipment.

26

GSM PLMN Siemens

GSM PLMN Siemens

EIREquipment Identity Register

Tasks:

• Storage of ME data (IMEI)

• Monitoring of IMEI: "white", "gray", "black" list

ME data:

• IMEI = International Mobile Equipment Identity

site: Dublin

CEIRCommon EIR

Tasks:

• Central, worldwide ME register • Worldwide ME theft prevention

= Type Approval Code TAC + Final Assembly Code FAC (manufacture site) + Serial Number SNR (device serial number)

+ Software Version Number SVR

Fig. 16

27

Siemens GSM PLMN

GSM Phase 2+: GPRS

For the introduction of GPRS the GSM PLMN has to be enhanced by:

� Gateway GPRS Support Node GGSN

� Serving GPRS Support Node SGSN

� Packet Control Unit PCU

� Channel Codec Unit CCU

� HLR Extension

� GPRS MS

Serving GPRS Support Node tasks:

� serves all GPRS-MS in SGSN area

� Routing / Traffic-Management

� Mobility Management functions,

� e.g. Location Update, Attach, Paging,..

� storing Location information

� Security & Access Control

� collecting charging data

� signaling with HLR, EIR, GGSN, MSC

Gateway GPRS Support Node GGSN tasks:

� Gateway to PDNs

� Protocol conversion

� Routing / Traffic Management

� Screening / Filtering

Packet Control Unit PCU tasks:

� protocol conversion

� radio resource management

The Channel Codec Unit CCU enables to transmit using the new Coding SchemesCS-1, CS-2, CS-3 and CS-4.

The HLR has to be extended to include the new type of GPRS subscriber data.

28

GSM PLMN Siemens

GSM PLMN Siemens

GGSN:• Gateway to PDNs

• Protocol conversion

� Routing / Traffic Management

� Screening / Filtering

X.25

Mobile

DTE

SGSNServing GPRSSupport Node

PSTN

InternetIntranet

GGSNGateway GPRSSupport Node

VMSC /

VLRGMSC

HLRextension

GSM Phase 2+: GPRS

ISDN

PCU

BSS

Channel Codec Unit CCU:

BTS-SW upgrade for new

Coding Schemes CS-1... CS-4

HLR Extension::GPRS subscriber data

(GPRS Register GR)

Packet Control Unit PCU:

• protocol conversion

• radio resource management

CCU

SGSN:• serves all GPRS-MS in SGSN area

• Routing / Traffic-Management

• Mobility Management functions, e.g. Location Update, Attach, Paging,..• storing Location information

• Security & Access Control

• collecting charging data

• signaling with HLR, EIR, GGSN, MSC,..

GiG

n

Gb G

r

For simplicity not all GPRS interfaces are shown

Fig. 17

29

Siemens GSM PLMN

Operation SubSystem OSS

The Operation SubSystem OSS undertakes operation and maintenance tasks. Thefunctions of the network/ network elements may be centrally monitored and (remote)controlled by the OSS. The control/operation & maintenance locally at each NetworkElement NE (hardware implementation of functional elements) as local operation andmaintenance is distinguished by the central, remote-controlled functionality of theOSS.

The functions of the OSS are performed by so-called Operation & MaintenanceCenters OMC. Depending on the manufacturer, there is sometimes spatial separationbetween the operation & maintenance of BSS and NSS (Siemens: OMC-B and OMC-S).

Important functions of the OSS:

� Management and commercial operation (subscriber, mobile equipment, billing)

� Sampling of information on network loads (statistical survey) for networkreorganization / optimization

� Security management

� Network configuration

� Remote operation of network elements

� Quality checks

� Preparation of maintenance work

30

GSM PLMN Siemens

GSM PLMN Siemens

MSC/VLR

MSC/VLR

HLR/AC

EIR

NSS

BSC

BTS

BSS

TRAU

WS

• Subscriber and equipment data

management

e.g. clearing services, bills

• Network operation, configuration

& management

• Collecting network load information

& compiling statistics

• Error detection & correction

• Security management

• Performance control

OMCOperation & Maintenance Center


Fig. 18

31

Siemens GSM PLMN

Telecommunication Management Network TMN

CCITT guidelines for Telecommunication Management Network TMN (CCITT M.30)designate the OSS as a telecommunication management system.

Seen from TMN level, the GMS-PLMN consists of a certain number of NetworkElements NE.

The TMN configuration of PLMN is ordered hierarchically into three levels:

� the lowest level is displayed by a large number of network elements NE of thePLMN

� the middle level is realized by a certain number of regional Operation &Maintenance Centers OMC

� the highest level is represented by operation systems, such as networkmanagement system, administration management, charging system, nationalOMC, etc.

OSS Telecommunication

Management System

according to

TMN

Network Elements NEs

regional

OMCs

TMN: Telecommunication Management Network

national

OMCs,administration, billing,

network management system,..

Operating systems

Fig. 19

32

GSM PLMN Siemens

Chapter 4

Procedures

Procedures

Procedures

Contents

2 Codes & Identities1 8 GSM Security Features2

19 Location Update 3 24 Call Setup / Call Handling4

Procedures Siemens

1 Codes & Identities

Procedures

Codes & Identities

CGI MCC MNC LAC CI

LAI

CC NDC SNMSISDN

MCC MNC MSINIMSI

X1

X2

X3

X4

X5

X6

X7

X8HLR-ID

Fig. 1

2

Siemens Procedures

GSM Service Areas & Codes

The GSM system is hierarchically ordered into service areas. To identify and addressa certain service areas codes are used.

International GSM Service Area

The international GSM service area is the sum of areas being served by GSMnetworks. A GSM subscriber may use all these GSM networks if his HPLMN hasRoaming Agreements with the VPLMN and his ME supports the correspondingfrequency range (GSM900 / GSM1800 / GSM1900).

National GSM Service Area

A national GSM service area contains one or more GSM-PLMN. The PLMN ofdifferent operators may supplement one another or overlap each other.

The following codes are important to identify a national GSM service area:

� Mobile Country Code MCC: The MCC consists of 3 digits; it is used e.g. for theInternational Mobile Subscriber Identity IMSI ,Location Area Identity LAI and CellGlobal Identity CGI.

� Country Code CC: The CC is the dialing code of the country in which the mobilesubscriber is registered. The CC consists of 2 or 3 digits and is used e.g. in theMobile Subscriber International ISDN number.

PLMN Service Area

A PLMN service area is administered by an operator. Several PLMN service areascan overlap within a country. Thus the individual PLMNs must have a clearidentification:

� Mobile Network Code MNC: The MNC is the mobile specific PLMN identification;it consists of 2 digits. The MNC is used in IMSI, LAI, CGI.

� National Destination Code NDC: NDCs identify the dialing code of a PLMN; itconsist of 3 digits. The NDC is used in MSISDN.

� Network Color Code NCC: The NCC is a PLMN discrimination code that is notunambiguous. It is used as short identity (length: 3 bits) of a particular PLMN inoverlapping PLMN areas or in border regions; it is used e.g. in the Base StationIdentity Code BSIC.

3

Procedures Siemens

Procedures Siemens

International

Service

Area Codes

National

MCC: Mobile Country Codee.g.: Aus 505, D 262, Lux 270

CC: Country Codee.g.: F 33, D 49, Lux 352

1 OperatorPLMN

MNC: Mobile Network Codee.g.: D1 01, D2 02, Eplus 03

NDC: National Destination Codee.g.: D1 171, D2 172, Eplus 177

MSC / SGSN „Switch“

Location Area LALA1

LA2

LAC: Location Area Code

LAI: Location Area Identity

Cell CI: Cell Identity

CGI: Cell Global Identity

MSC-Identity

Hierarchy

of GSM

Service Areas

/ Codes

MCC:

CC:

MNC:

NDC:

NCC:

LAC:

LAI:

CI:

CGI:

Mobile Country Code

Country Code

Mobile Network Code

National Destination Code

Network Colour Code

Location Area Code

Location Area Identity

Cell Identity

Cell Global Identity

Fig. 2

4

Siemens Procedures

MSC/VLR Service Area

GSM-PLMN are subdivided into one or more MSC/VLR service areas. An attachedmobile subscriber is registered in the VLR, which is associated to his Visited MSC.The MSC/VLR Id. is stored in the HLR, so that an MTC is possible.

Location Area LA

The LA is (in classical GSM) is stored as the most precise information of the(attached) subscribers current location. This information is stored in the VLRassociated to the VMSC. If the MS turns from one LA to another, a Location UpdateProcedure is necessary. The size of a LA is configured by the operator according tothe traffic or population density and the behavior of the mobile subscriber. A LocationArea can encompass one or more radio cells that are controlled by one or more BSC,but never belong to different MSC areas. Location Area identities are:

� Location Area Code LAC: The LAC serves to identify a LA within a GSM-PLMN.The LAC length is 2 bytes.

� Location Area Identity LAI = MCC + MNC + LAC; the LAI serves as anunambiguous international identification of a location area.

BTS Service Area: the Cell

The cell is the smallest unit in the GSM-PLMN. A defined quality of the receivedsignal must be guaranteed within a cell. If a MS leaves the range of a cell during aconnection, a handover to the next cell is initiated. Cell identifications are:

� Cell Identity CI: The CI allows identification of a cell within a location area. The CIlength is 2 bytes.

� Cell Global Identity CGI = MCC + MNC + LAC + CI = LAI + CI; the CGIrepresents an international unambiguous identification of a cell.

� Base Transceiver Station Identity Code BSIC = NCC + BCC (Base Station ColorCode); The BSIC represents a non-unambiguous short identification (NCC: 3 bit;BCC: 3 bit) of a cell. The BSIC is emitted at a regular rate by the BTS. It enablesthe MS to differentiate between different surrounding cells and to identify therequested cell in a random access.

5

Procedures Siemens

Procedures Siemens

National &

PLMN Codes Example*:

Germany

CC = 49

MCC = 262D1

Telekom

D2Mannesmann

Eplus

NDC = 171

MNC = 01

NDC = 172

MNC = 02

NDC = 177

MNC = 03

NDC = 178

MNC = 04

E2Viag Intercom

CC NDC SNSubscriber Number

MSISDNMobile Subscriber ISDN Number

MCC MNC MSINMobile Subscriber Id. No.

IMSIInternational Mobile Subscriber Identity

X1

X2

X3

X4

X5

X6

X7

X8HLR-ID

Subscriber Identities

* This figure has just an illustrative purpose and does not reflect the actual MSC areas of any German PLMN operator.

Fig. 3

6

Procedures Siemens

Identifier:

MSC / VLR - Identity

LAI = MCC + MNC + LAC

CGI = LAI + CIMSC / VLR

MSC / VLR

MSC / VLR

MSC / VLR

MSC / VLR

LALA

LA

LA

LA

CellCell

Principle:

MSC, Location

& Cell Area

MCC MNC LAC CI

LAI

Fig. 4

Subscriber Identities:

� International Mobile Subscriber Identity IMSI = MCC + MNC + MSIN (MobileSubscriber Identification Number); IMSI length = 3 + 2 + 10 digits. The IMSI is theunique identity of a GSM subscriber. It is used for signaling and normally notknown to the subscriber. Often die first two MSIN digits are taken to specify theusers HLR in the PLMN (operator dependent).

� Mobile Subscriber ISDN number MSISDN = CC + NDC + SN. MSISDN length: 2/ 3 + 3 + max. 7 digits = max. 12 digits. The MSISDN is "the users telephonenumber". A user has one IMSI (with one contract), but he can have differentMSISDN (e.g. for fax, phone,..).

� Temporary Mobile Subscriber Identity TMSI: The TMSI is generated by the VLRand temporarily allocated to one MS. It is only valid in this MSC/VLR service.When changing to a new MSC area, a new TMSI has to be allocated. The TMSIconsists of a TMSI Code TIC with length 4 bytes. Often the TMSI is used togetherwith the LAI.

7

Procedures Siemens

2 GSM Security Features

Procedures

GSM Security Features

Security Features:

• Authentication

• Ciphering

• TMSI allocation

• IMEI check

Fig. 5

8

Siemens Procedures

Security Features

In GSM the security of a mobile subscriber is ensured by several features.

� Authentication: protects the network operator and mobile subscriber againstunauthorized network use.

� Ciphering: is used to prevent eavesdropping of radio communications.

� Temporary Mobile Subscriber Identity TMSI allocation: protects thesubscribers identity in the initial access phase, where no ciphering is possible.

� IMEI check: prevents the usage of stolen/non-authorized mobile equipment.

Security aspects are described in the GSM Recommendations:

� 02.09: “Security Aspects"

� 02.17: "Subscriber Identity Modules"

� 03.20: "Security Related Network Functions"

� 03.21: "Security Related Algorithm"

Prerequisites for Authentication and Ciphering

For authentication and ciphering, the Authentication Center AC and the SIM card areimportant; they store the following data:

� IMSI (International Mobile Subscriber Identity)

� Ki (Individual Key)

� A3, A8: Algorithms for the creation of authentication and ciphering parameters

Furthermore, for ciphering the algorithm A5 is stored in the Mobile Equipment. Thisalgorithm can be found in the BTS, too.

9

Procedures Siemens

Procedures Siemens

BSS

MSC / VLR

HLR AC

EIR

BTS

NSSSIM

IMSI

Ki

A3, A8

A5

ME

IMEI

IMEIPrerequisites

for Authentication

& Ciphering

Fig. 6

10

Procedures Siemens

TriplesCalculation

Random

Number

Generator

A3(Ki, RAND) = SRES A8(Ki, RAND) = Kc

RAND = RANDom numberSRES = Signed RESponseKc = Cipher Key

Data-

base

IMSI

Algorithm

A3

Algorithm

A8

RAND SRES Kc

Triple

ACAuthentication

Center

RAND

KcSRES

Ki

Fig. 7

Triples

The triples are parameters, which are necessary for authentication and ciphering.They are produced in the Authentication Center AC and consist of:

� RAND (RANDom number)

� SRES (Signed RESponse): the reference value for the authentication

� Kc (Cipher Key): key necessary for ciphering.

The calculation of a triple in the AC occurs in the following manner:

� For the subscriber with a particular IMSI the reference value of authenticationSRES is calculated by the algorithm A3 from the users individual key Ki and therandom number RAND produced by a random number generator.

� The cipher key Kc is calculated by the algorithm A8 from the individual key Ki andthe random number RAND.

� RAND, Kc and SRES make together a complete triple.

At the request of the VLR, several triples are generated for each mobile subscriber inthe AC and transferred to the VLR via the HLR on request.

Remark: The individual key Ki is only stored in the AC and the SIM card. Different tothe IMSI and the triples, it is never transmitted through the network. For all signalingprocedures the users IMSI is used.

11

Siemens Procedures

Authentication

The authentication checks the real identity of a user, i.e. his authorization to takeaccess to the network. Actually it is checked, whether the secret individual Key Kistored on the SIM card is identically to the one stored for this user in theAuthentication Center or not. The authentication procedure is or can be initiated bythe VLR in the following cases:

� IMSI Attach

� Location Registration

� Location update with VLR change

� call setup (MOC, MTC)

� activation of connectionless supplementary services

� Short Message Service (SMS)

Authentication Procedure

1. the VLR recognizes the need for an authentication; in the case, that no / no moreTriples are available in the VLR it requests a set of Triples from the HLR

2. the Triples are generated in the AC (see above) and sent via HLR to the VLR

3. the VLR sends the RAND to the MS; the SIM card calculates the SRES using Ki,A3 and RAND (see above)

4. the MS sends the SRES back to the VLR; the VLR compares the SRES in thetriple with the SRES calculated by the MS; if they coincide, the network accesswill be authorized and the general procedure will continue, otherwise

5. the access will be refused and the "Authentication Refused" message will be sentto the MS

12

Procedures Siemens

Procedures Siemens

requests

triples

sends triples

sends RAND

sends SRES

MS BSS MSC VLR HLR/AC

1

2

3

4coincidence

check

4

5

sends

“Authentication

refused"

55

Authentication

Um

A B D

3

3

4

• Location Registration LR

• LUP with VLR change

• Call Setup: MOC / MTC / SMS

• Activation of connectionless supplementary services

with:

*1

*1 only if no more Triples

available in VLR

*2 only if coincidence

check negative

*2

Fig. 8

13

Siemens Procedures

Ciphering

Ciphering regards the security aspects of the information exchange between theMobile Station (MS) and the Base Station (BTS) on the air interface Um. Userinformation (speech/data) and signaling information are ciphered via air interface Um(UL & DL). An exception is given by the initial signaling, before the cipher commandis sent from the network side. At initial signaling data exchange ciphering is notpossible, because the users identities are necessary prerequisite for the generationof ciphering parameters. The cipher command is given after transmission of the useridentity (TMSI / IMSI) and the authentication procedure. Ciphering / Deciphering iscarried out in the BTS and in the MS.

The GSM Recommendation (02.16) of Phase 2 states that up to 8 logically differentencryption algorithms (incl. "no ciphering") should be used. The reason for this is theintention

a) to assign different algorithms to different countries and

b) to provide MS, which do not use the A5-1 algorithm, with the possibility ofroaming in different GSM-PLMN networks.

Currently 3 algorithms are defined:

� A5-0: no ciphering for COCOM countries

� A5-1: "strict" cipher algorithm (originally MoU algorithm) for MoU-1 countries , A5-1comes from GB; due to military origin (NATO), high security arrangements are tobe regarded

� A5-2: "simplified" cipher algorithm for MoU-2 countries (without COCOMcountries);

Remark: A5-0 is implemented in every MS and every BTS to enable access of everyMS in every network. Additionally A5-1 or A5-2 can be implemented.

14

Procedures Siemens

Procedures Siemens

Ciphering

• Prevents eavesdropping in Um

• Application in user information and signalling

• Exception: initial signalling

ciphered information

Cipher commandMS BTS

A5 A5

Rec. 02.16: max. 8 cipher algorithms

A5-0: no ciphering; COCOM countries

A5-1: "strict" ciphering; MoU-1 countries

A5-2: "simple" ciphering; MoU-2 countries (except COCOM)

Rec. 02.16: max. 8 cipher algorithms

A5-0: no ciphering; COCOM countries

A5-1: "strict" ciphering; MoU-1 countries

A5-2: "simple" ciphering; MoU-2 countries (except COCOM)

Fig. 9

15

Procedures Siemens

Ciphering& Authentication

Authentication:A3(Ki, RAND) = SRES

Ciphering:A8(Ki, RAND) = Kc

A5(Kc,TDMA-No.) = CStext XOR CS = ciphered text

Ciphering:

A5(Kc,TDMA-No.) = CS

text XOR CS = ciphered text

Authentication

& ciphering:generates RAND

A3(Ki, RAND) = SRES

A8(Ki, RAND) = Kc

Authentication:SRES comparison

MS

BTS:

A5

BTS

Umencoded

transmission !

VLR:

IMSI

Triples

AC:

A3, A8,

IMSI,Ki

VLR AC

Triples:

RAND,

SRES, Kc

RAND, KcRAND

ME:

A5

SIM:

A3, A8,

Ki, IMSI SRESSRES

XOR

XOR

plain text

cipher sequence

ciphered text

cipher sequence

plain text 0 1 0 0 1 0 1 1 1 0 0 1...

0 0 1 0 1 1 0 0 1 1 1 0...

0 1 1 0 0 1 1 1 0 1 1 1...

0 0 1 0 1 1 0 0 1 1 1 0...

0 1 0 0 1 0 1 1 1 0 0 1...

CS: cipher sequence

Fig. 10

Ciphering process

Transmitter/receiver must use the same cipher algorithms.

In order to handle ciphering individually for every user, the individual key Ki (stored inthe SIM card and the AC) is used.

The cipher key Kc is transmitted after ciphering from the VLR to the BTS. The MS isable to calculate Kc (after receiving RAND in the authentication procedure) byalgorithm A8 from RAND and Ki.

A 114 bit long cipher sequence is calculated using the cipher algorithm A5, the cipherkey Kc and the TDMA frame number (broadcasted cyclically by every BTS over thecell area).

The speech, data and signaling information are ciphered / deciphered in 114 bit longsequences being connected in a so-called "eXclusive OR" XOR operation.

Deciphering follows exactly the same scheme as ciphering, as the XOR operationyields the original values after double application of XOR (using the same ciphersequence).

To start ciphering, the network sends a cipher start command, which has to beacknowledged by the MS (being the first ciphered information).

16

Procedures Siemens

TMSI

Allocation

• Network requires subscriber Id. for call setup

• Id. necessary for triples calculation

• Start of transmission of Id. uncoded

• TMSI prevents eavesdropping of subscriber Id. (IMSI)

• New TMSI with VLR change & usually at call setup

• Network requires subscriber Id. for call setup

• Id. necessary for triples calculation

• Start of transmission of Id. uncoded

• TMSI prevents eavesdropping of subscriber Id. (IMSI)

• New TMSI with VLR change & usually at call setup

MS BSSsends

TMSI

= LAI + TIC

MSC VLR HLR/

AC

IMSI

� Ki �

Triples

determines

IMSI from

TMSI

TMSI TMSI IMSI

Authentication

Ciphering Triples

new

TMSI

assigns

new

TMSI

stores

new

TMSI

For LA change with MSC/VLR change:

• New VLR identifies old VLR by TMSI

• Subscriber data: query of old VLR

For LA change with MSC/VLR change:

• New VLR identifies old VLR by TMSI

• Subscriber data: query of old VLR

Fig. 11

TMSI Allocation

Ciphering protects the user from being eavesdropped. However, the ciphering withKc requires that the network is aware of the identity of the mobile subscriber withwhom it is in contact. Thus, during the initial phase of communication setup, when theidentity of the mobile subscriber is still unknown, the transmitted signaling informationcan not be ciphered. During this phase a third party may identify a subscriber and thedesired service.

In order to protect the identity of the subscriber in this phase, a temporaryidentification of the subscriber is distributed: the Temporary Mobile SubscriberIdentity TMSI.

The TMSI is used instead of the real user identity, the International Mobile SubscriberIdentity IMSI. This TMSI is allocated by the VLR, which is associated to the VMSC.The MS usually identifies itself with the TMSI in the initial access phase to the VLR.The VLR uses this TMSI to re-identify the IMSI. This is only possible if the TMSI hasbeen allocated by the same VLR. If not, the VLR has to request the VLR, which hasallocated the TMSI to the MS, to deliver the IMSI. Therefore, the TMSI is in mostcases transmitted together with the old LAI, which identifies uniquely a VLR. Therequest VLR - VLR is only possible, if both VLR belong to the same PLMN.Therefore, the IMSI has to be transmitted via Um at the first registration in a newPLMN and obviously at the very first usage of the SIM card (i.e. in the case ofLocation Registrations).

A new TMSI (TMSI re-allocation) can optionally be allocated to the MS after everyauthentication & cipher start (and the optional IMEI check).

17

Procedures Siemens

IMEI Check

MS BSS

IDENT_RSP

EIRauthentication

ciphering

IDENT_REQ

IMEI

MSC/VLR

Initiates

authentication

Ciphering

Initiates

IMEI Request

(Identity Request)

Checking

IMEI

(white, grey

or black list)

TACType Approval Code

24 Bit

FACFinal Assembly Code

8 Bit

SNRSerial Number

24 Bit

SVNSoftware Version Number

(spare) 4 Bit

ME

identified

by

IMEI

• Recognise stolen, expired and faulty MEs• Recognise stolen, expired and faulty MEs

Fig. 12

IMEI Check

In contrast to the other security mechanism authentication, ciphering and TMSIallocation, the check of the International Mobile Equipment Identity IMEI is optional. Itdepends on the operators decision whether a EIR is implemented and IMEI checksare done.

IMEI check serves to identify stolen, expired or faulty mobile equipment. A IMEIclearly identifies a particular mobile device and contains information about the placeof manufacture, type approval code and the serial number of the equipment.

The IMEI consists of: Type Approval Code TAC, Final Assembly Code FAC, SerialNumber SNR and a Software Version Number SVN.

If a IMEI check in the PLMN is intended, the Mobile Station MS will be requested tosubmit the IMEI during call setup after authentication and cipher command. The MSsends back its IMEI. The IMEI is routed to the EIR of the PLMN. A check occurs hereto find out whether the IMEI is registered on the black or gray list, i.e. whether the MSis blocked from further use of the PLMN, or whether it has to be observed.

18

Procedures Siemens

3 Location Update

Procedures

Location Update

MS

BTS

request

Location Update

Fig. 13

19

Siemens Procedures

Location Registration / Location Update

Information of the current location of a mobile subscriber are necessary to built up aconnection to the subscriber, i.e. to start a Mobile Terminating Call MTC. To keeptrack of the users current location the Location Registration / Update procedures areused. Always the MS is responsible to initiate this Location Registration /Update procedures. It informs the network on its current Location Area. TheLocation Area information is stored in the currently responsible VLR. The identity ofthis VLR is stored in the users HLR.

If a MS is "new" in a PLMN a Location Registration is performed. "New" is defined asthe very first usage of a SIM card or a first access after changing the PLMN.

In case of a Location Registration the network needs the IMSI of the MS, becauseeither no TMSI has been allocated before to the MS (in case of first SIM usage) or itis impossible to regenerate the IMSI from the TMSI, because the new VLR is not ableto get into contact with the old VLR (e.g. in case of PLMN changes). After LocationRegistration, in the following Location Updates are used to update the locationinformation in the PLMN. In a Location Update only the TMSI is transmitted via Um.

There are three reasons to perform a Location Update Procedure LUP:

� Location Update with "IMSI Attach": If a MS is switched on / off, the network isinformed about the change of the current MS state, i.e. whether to be reachable ornot. Therefore, when being switched on / off, the MS performs an "IMSI Attach" /"IMSI Detach" procedure. The information whether the MS is Attached / Detachedis stored in the VLR. If an "IMSI Attach is performed it is connected with a LUP.

� Normal Location Update: Normally a LUP is performed after the MS hasrecognized that it has crossed the boarder between two different Location Areas.The MS is able to recognize the LA change, because it always listens around tothe broadcast information of all cells in its environment, which include the CGI(and so the LAI). If the LAI of the strongest cell changes, a LUP is performed.

� Periodical Location Update: A periodic LUP is initiated by a MS at regularintervals. If the VLR does not receive the LUP after a certain time, a "MobileStation not reachable" flag is set.

The LUP is not performed during the duration of a connection. In this case, the LUPis performed after call release.

20

Procedures Siemens

Procedures Siemens

LAI =

2620533

MS

BTS

BCCH:

CGI =

26205A64B...

Location

Registration/

Update

• Location Registration: initial MS registration in PLMN

• Location Update

• no LU during connection!

request

Location Update

3 types of Location Update:

• normal

• periodic

• with IMSI attach

Fig. 14

21

Procedures Siemens

requests triples

triples

requests LUP,

LR: IMSI

LUP: TMSI

requestssubscriber data;

sends VLR-Id.& LMSI


11

1

2

3

4

5

6

sends data7

sends TMSI =

LAI + TIC

Location Update LUP

77

authentication, ciphering, (IMEI check)

*1


available in VLR

Fig. 15

Location Update Procedure LUP without change of the MSC area

1. The MS recognizes that the LAI has changed. It requests a LUP, identifying itselfwith the TMSI or IMSI. The request and the identity are forwarded to the VLR.

2. The VLR re-identifies the IMSI from the TMSI. If no / no more Triples areavailable in the VLR, it requests triples from the AC via the HLR.

3. The AC generates a set of Triples and delivers them via HLR to the VLR.

4. The VLR stores the Triples and initiates the Authentication, then gives the cipherstart command and initiates an IMEI check (optional).

5. If the Authentication, cipher start and IMEI check are successful, the VLR needsfor call setups the subscriber data. In case of a LR, they are have not beenstored before in the VLR and so they have to be requested from the HLR.Together with this request, the VLR delivers its identity and the information,where this subscriber is stored in the VLR, i.e. the Local Mobile SubscriberIdentity, to the VLR.

6. The HLR stores the VLR identity and LMSI and transmits the requestedsubscriber data to the VLR.

7. The VLR stores the subscriber data and assigns a TMSI (LR: mandatory) or anew TMSI (LUP: only with MSC/VLR change) to the MS. This TMSI is transmittedtogether with the VLRs acknowledgement, that the LUP has been successful, tothe MS. There, the new TMSI and LAI are stored on the SIM card.

22

Procedures Siemens

old

VLR

MSC

BSS

new

VLR

MSC

BSS

HLR

AC

Um

LA change

with MSC / VLR change

41

1

16

6

6

3

2

5

7

7

7

Location Update Procedure LUPincl. MSC - VLR change

Fig. 16

Location Update Procedure LUP with VLR change

1. The MS recognizes that the LAI has changed. It requests a LUP, identifying itselfwith the TMSI. The request and the identity (TMSI in combination with the oldLAI) are forwarded to the new VLR.

2. The new VLR receives the TMSI and LAI. It recognizes from the LAI, that theTMSI has been allocated by another VLR (old VLR). Thus, the VLR is not able tore-identify the IMSI from the TMSI and has no chance to request the subscriberdata from the HLR. Therefor, the new VLR calculates the address of the old VLRfrom the LAI and transmits the TMSI to the old VLR and requests it to deliver theusers IMSI. The old VLR delivers the IMSI and the remaining Triples to the newVLR. Remark: If this step 2 is not possible (e.g. line break between old and newVLR) the new VLR commands the MS to transmit the IMSI directly.

3. The new VLR uses the IMSI to calculate the users HLR. The new VLR transmitits identity and LMSI to the HLR and requests the HLR to deliver the subscriberdata and, if necessary, a set of Triples.

4. The HLR stores the new VLRs identity and LMSI, confirms the information,supplies the subscriber data and, if necessary, the Triples.

5. The HLR informs the old VLR to erase the stored data set of this subscriber.

6. The VLR now starts authentication, ciphering and (optionally) IMEI check.

7. The VLR allocates a new TMSI to the MS.

23

Procedures Siemens

4 Call Setup / Call Handling

MOCMS starts network access

(PLMN, ISDN, PSTN)

MTCMS is contacted

MMCMS1 starts network access

MS2 is contacted

MICSpecial case MMC:

both MSs in same MSC area

Procedures

Call Setup

Fig. 17

24

Siemens Procedures

Call Setup

Different procedures are necessary depending on the initiating and terminating party:

� Mobile Originating Call MOC: Call setup, which are initiated by an MS

� Mobile Terminating Call MTC: Call setup, where an MS is the called party

� Mobile Mobile Call MMC: Call setup between two mobile subscribers; MMC thusconsists of the execution of a MOC and a MTC one after the other.

� Mobile Internal Call MIC: a special case of MMC; both MSs are in the same MSCarea, possibly even in the same cell.

Mobile Originating Call MOC

1. Channel Request: The MS requests for the allocation of a dedicated signalingchannel to perform the call setup.

2. After allocation of a signaling channel the request for MOC call setup, includedthe TMSI (IMSI) and the last LAI, is forwarded to the VLR

3. The VLR requests the AC via HLR for Triples (if necessary).

4. The VLR initiates Authentication, Cipher start, IMEI check (optional) and TMSIRe-allocation (optional).

5. If all this procedures have been successful, MS sends the Setup information(number of requested subscriber and detailed service description) to the MSC.

6. The MSC requests the VLR to check from the subscriber data whether therequested service an number can be handled (or if there are restrictions which donot allow further proceeding of the call setup)

7. If the VLR indicates that the call should be proceeded, the MSC commands theBSC to assign a Traffic Channel (i.e. resources for speech data transmission) tothe MS

8. The BSC assigns a Traffic Channel TCH to the MS

9. The MSC sets up the connection to requested number (called party).

Remark: This MOC as well as the MTC described in the following describes only theprinciples of an MOC / MTC, not the detailed signaling flow.

25

Procedures Siemens

Procedures Siemens

requests

triples

triples

Setup (Phone No.,..)

Channel Request sends

subscriber Id.

TMSI (IMSI)


identification +

authentication

request

1 2 2

3

3

4

5

requests call

information

6

6

sends info78

9

Setup connection to B-subscriber

Traffic Channel

assignment

commands

channel assignment


authentication + start ciphering + IMEI check + new TMSI

*1


available in VLR

Fig. 18

26

Siemens Procedures

Mobile Terminating Call MTC

In the case of a MTC the mobile subscriber is the called party. The MTC call flowdiffers in dependence on the initiating party. In this example the initiating party issubscriber on an external network.

1. After analysis of the MSISDN (CC and NDC) a request to set up a call istransmitted from an external exchange to the GMSC.

2. The GMSC identifies the users HLR from the MSISDN. It starts a so-calledInterrogation to the HLR to get information of the subscribers current location.

3. The HLR identifies the subscribers IMSI from the MSISDN and checks thesubscribers current location, i.e. the VLR address. The HLR informs the VLRabout the call and requests a Mobile Station Roaming Number MSRN (includingthe VMSC address) from the VLR. The request to the VLR includes the LMSI,which enables the fast access to the users data in the VLR.

4. The VLR transmits the MSRN to the HLR, which forwards this number and theIMSI to the GMSC. If the VLR has information, that the MS is Detached currently,the call is rejected / forwarded to the Mailbox.

5. The GMSC uses the MSRN (including the VMSC address) and IMSI to get intocontact with the VMSC.

6. The VMSC requests information (LAI, TMSI) for call setup from its VLR

7. The VLR sends these data.

8. The VMSC uses the LAI to start the Paging procedure. Paging means to searchto MS in the total Location Area (the precise cell is not known).

9. The MS responses the Paging, i.e. from now on its cell is known.

10. This topic includes: Authentication, cipher start, IMEI check and TMSI Re-allocation.

11. The MSC transmits the Setup information to the MS, commands the BSC toallocate a Traffic Channel to the MS and switches through the connection.

27

Procedures Siemens

Procedures Siemens

call

requestInterrogation:

MSRN request

sends data

requests data

(LAI, IMSI)

MS

BTS

sends IMSI

requests MSRN

1

10

23

4

5

6

Paging

7

9

8


BTS

BTS

4

sends MSRN5 5

Paging

8

Paging Response9

10 10

connection request

authentication + ciphering + IMEI check + new TMSIcall through switching11 11 11 11

Assignment of Traffic Channel

VLR HLR GMSCVMSC

Fig. 19

28

Procedures Siemens

EIR

HLR AC

VLR

VMSC

VLR

VMSC

trafficchannel

BSC

BSC

NSS Network Switching Subsystem RSS Radio Subsystem

Mobile Mobile Call MMC

Mobile Internal Call MIC

BTS

BTS

EIR

HLR AC

VLR

VMSC

BSC

BSC

NSS Network Switching Subsystem RSS Radio Subsystem

BTS

BTS

trafficchannel

Fig. 20

Mobile - Mobile Call MMC / Mobile Internal Call MIC

MMC and MIC are only special cases / combinations of the MOC and MTC.

Mobile Mobile Call MMC

The MMC is a call setup initiated by a MS and terminating at a MS. Thus, MOC andMTC are executed one after the other.

For the call setup of a MMC the same procedures are valid as in the case of MOCand MTC for the call setup between a mobile subscriber and a fixed subscriber. Inthe case of PLMN internal MMC, instead of inquiring the GMSC the VMSC of thecalling party queries the HLR of the called party.

Mobile Internal Call MIC

A special case of the MMC is represented by the MIC. Here, both mobile subscribersare in the same MSC area or even in the same cell. No shortening of the proceduretakes place here. MOC and MTC procedures are executed after each other, the onlydifference is that the MSC involved is VMSC for both, the calling and called party.

29

Procedures Siemens

OACSUOff Air Call Set Up

BTS

call setup:

signalingB- subscriber

A- subscriber

MS B-subscriber

answers

B-subscriber

answers

traffic channel

assignment

Not for:

• International calls

• Data connection

• Emergency calls

• Delayed call setup

• No traffic channel assignment until

B-subscriber answers / timer expires

Fig. 21

Off Air Call Set Up OACSU

The OACSU is used in case of overload on the radio interface (a lack of TrafficChannels). It is helpful to overcome short term bottleneck situations without rejectingcall requests.

If there is currently a lack of Traffic Channels OACSU enables to delay the TCHallocation until there is an answer of the called participant. In most cases this willneed several 10 s. There is a high probability that during this time another call isfinished and this TCH is then reserved for the delayed TCH allocation.

OACSU can theoretically be used for MOC and MTC.

In the case of OACSU so-called partial connections are set up. After the TCH is as-signed, the partial connection is completed. The delay of the TCH assignment ismonitored by a timer. When the time frame has run out, a TCH is assigned. TheOACSU can lead to an announcement for the called party, if he/she picks up thephone before the delayed assignment of the TCH.

Restraints for OACSU:

� not for international calls

� not for data connection

� not for emergency calls

30

Siemens Procedures

Handover HO: Handover Types

Handover HO are a change of the physical channel during a current connection.There are various types of handover:

� Intra-Cell Handover: In the case of Intra-Cell Handover, a physical channel withina cell is changed. A reason for this may be an interference in the frequencycurrently being used. Frequency and/or Time Slot can be changed. Therefore itdiffers from the feature "frequency hopping", in which the frequency is changedafter a certain algorithm, but the time slot is never changed. Frequency hoppingand Intra-Cell Handover exclude each other. The intra-cell handover is realizedinternally in the BSS, i.e. the BSC decides without MSC involvement. Only themessage "handover performed" is sent to the MSC after the handover.

� Intra-BSS Handover: An Intra-BSS Handover is carried out between two cells ofthe same BSS. The procedure is decided and performed by the BSC (no MSCinvolvement). The MSC is informed only after the handover ("handoverperformed").

� Intra-MSC Handover: An Intra-MSC handover is a handover between two BSSsof the same MSC. The MSC decides about this Handover and switches betweenthe two BSCs.

Inter-MSC Handover: A Inter-MSC Handover include at least two MSCs. TheMSC has to decide and to switch. Inter-MSC handovers are one of the mostcomplicated GSM procedures, in particular in the case of MSCs made by differentmanufacturers. One has to distinguish between "Basic Inter-MSC Handover" and"Subsequent Inter-MSC Handover".

Basic Inter-MSC Handover: If a MS changes for the first time from the area of anMSC (A) to the area of a MSC (B), this is described as Basic Handover.

Subsequent Handover: If the MS also leaves the MSC (B) area and moves into thearea of a further MSC (C) or returns to the area of the old MSC (A), this follow-onhandover is called Subsequent Inter-MSC Handover. The handover is controlledby the initial MSC, which is called MSC (A) = Anchor MSC. In a Subsequent Inter-MSC Handover with MSC (C) for a short time three MSCs are connected for onecall. The connection MSC (A) - MSC (B) is released after successful set up ofconnection between MSC (A)and MSC (C).

The Anchor MSC is responsible for billing. This is the reason, why Inter-PLMNHandover, i.e. Handover between different PLMNs are normally not performed.

31

Procedures Siemens

Procedures Siemens

Handover Types

Intra-cell

BSCBTS

f 1, TS 1

f 2, TS 2

Intra-BSS

BSC

BTS

BTS

MSC

Handover

performed

Intra-MSC

MSC

BSS

BSS

Inter-MSC

MSC - BMSC - A

MSC - C

basic

subsequent

MSC

Handover

performed

Fig. 22

32

Siemens Procedures

Handover Decision

The handover algorithm is based on periodically measurements of MS and BTSconcerning the strength and quality of the received signals. The MS measures qualityand strength of the connection and the strength of the serving BTS and that of thesurrounding BTSs. The BTS measures quality and strength of the connection as wellas the distance MS - BTS (Timing Advance TA).

The result of the MS measurements is transmitted to the BTS. The BTS adds its ownmeasurements and transmits the data as "Measurement Report" to the BSC.

The BSC has to decide, whether a handover is necessary or not. The decision isdetermined by the comparison between the current measured values and thethreshold values. If no threshold values are exceeded, the BSC analyses whether another BTS as the current one would enable a better air interface quality. Differentother aspects have to be taken into account, e.g. the current load of the cells.Furthermore, so-called "Ping-Pong Handover" should be prevented.

If an Inter-cell handover is initiated, the criterion of availability of surrounding cells isused to set up a list of suitable handover destinations in a declining order of priority.This list forms the basis for the final handover decision that is carried out by the BSC(in case of Intra-BSS Handover) or by the MSC (in case of Inter-BSC / -MSCHandover).

Handover criteria are e.g.:

� Strength of the received signal (UL and DL)

� Quality of the received signal (UL and DL)

� Distance MS - BTS (Timing Advance, UL)

� Signal strength of suitable surrounding cells (UL, BCCH)

� Interference that decrease the signal quality (UL and DL)

33

Procedures Siemens

Procedures Siemens

Measurement:

connection quality & strength:

strength of serving BTS &

surrounding BTSs

HandoverDecision

MS

Measurement:

connection quality & strength,

distance measurement (TA)BTS

Measurement report

Timing Advance,Power control

BSC

HO

decision

Measurement value processing

(averaging, limit values,..)

Evaluation list

(suitable BTSs for HO...)

Initiation of HO type

HandoverBSC/

MSC

Measurementreport

Fig. 23

34

Procedures Siemens

BTS

BTS

BTS

BTS

BTS

BTS

BTS

MSC (A)

VLR

Handoverexample

MSC (B)

VLR

BSC

BSC

BTS

Level:cell Acell B

cell C

BTS

BSC to MSC (A):

HO please!

cell B

�� MSC (B)

A

B

C

1. BSC: HO necessary

2. Parallel connection setup

3. MS changes phys. channel

4. Original connection released

Fig. 24

Handover Example: (Basic) Inter-MSC Handover

1. During an existing connection, the MS permanently measures the quality andpower level of the received information and measures the strength of its own andthe surrounding BTS. Furthermore, the BTS measures the quality and strength ofthe connection and the Timing Advance. The results are as measurement reportto the BSC. The BSC analyses the need for Handover. If an Handover isnecessary, the BSC creates a list of preferable cells to which the Handovershould be performed. If an Handover to a cell of another BSC / MSC isnecessary, the information is forwarded to the MSC (A). In this example, aHandover from Cell A to Cell B is preferable. On basis of the BSC information,the MSC (A) decides to initiate a Basic Inter-MSC Handover to MSC (B),because Cell B is in the service area of MSC (B).

2. MSC (B) requests the BSC, which is responsible for Cell B to allocate resourcesfor this connection and prepare network transmission capacities for the call. Asecond connection is built up parallel to the existing connection. The DLinformation is split and delivered to both BTS.

3. MSC (A) gives command to the MS (via BSC) to change the physical channel.Changing the physical channel, the MS immediately is connected to Cell B.

4. The initial connection is released, the resources are set free for otherconnections. The users data are still transmitted via MSC (A); it is the Anchor-MSC.

35

Procedures Siemens

Emergency

Call

call setup:

Emergency Call

Center

MS

without:

• Authentification

• Ciphering

• IMEI check

• TMSI-Reallocation

Emergency call:• Priority treatment

• no security features

• fast call setup

• usually always possible,

even without valid SIM card

MSC

• Direct connection

• Supplies location info

S O S

Fig. 25

Emergency Call

The connection set up for the Tele Service "Emergency Call" is similar the that of theMobile Originating Call MOC.

The mobile subscriber starts this service either by pressing a SOS key or by dialingan emergency service number (often: 112).

The setup follows the MOC signaling flow. Differences are:

� no Authentication is necessary

� no Ciphering will be used

� no IMEI check is performed

� no TMSI Re-allocation is performed

A short call setup is resulting in this lack of security features. Furthermore, theEmergency Call should always be possible with any MS, even without a valid SIMCard.

Emergency calls are treated with precedence. This may also lead to the release ofother existing connections.

The BSS always delivers the location of the emergency call to the MSC. Dependingon this origin, the emergency connection is then transmitted from the MSC to theregionally responsible Emergency Call Center. The available location information canbe delivered to the Emergency Call Center, too (operator dependent).

36

s

Short Message Service SMS transmission (MT-SMS)

MS attached (i.e. reachable):

� A Short Message Service Center SM-SC (out of the scope of the GSM Rec.) triesto transmit the SMS to the requested MS via GMSC.

� The GMSC performs an Interrogation to the HLR to get knowledge about thecurrent VMSC.

� The HLR requests the VLR for an MSRN and forwards this to the GMSC.

� The GMSC gets into contact with the VMSC and the SMS is delivered to the MS.Different to the MOC, no Traffic Channel allocation is necessary in case of SMStransmission. The SMS can be transmitted via Signaling Channel.

MS Detached (not reachable):

� The SM-SC tries to transmit the SMS to the requested MS via GMSC.

� The GMSC performs an Interrogation to the HLR to get knowledge about thecurrent VMSC.

� The HLR requests the VLR for an MSRN. This is not possible, because thesubscriber is Detached and the VLR stores this information.

� In the following, a SMS flag is set in the VLR and in the HLR. Furthermore, theHLR stores the address of the SMS-SC.

� The HLR informs the GMSC that the SMS can not be delivered and the GMSCrejects the request of the SM-SC. The SMS is still stored in the SM-SC.

� If the MS is switched on again, an IMSI Attach procedure is performed to the VLR.

� Due to the SMS flags, the VLR informs the HLR, that the MS is reachable again.

� The HLR requests via GMSC the SM-SC to start the SMS transmission again.

37

Procedures Siemens

Procedures Siemens

SMS-

GMSCSM-SC

SMS Service CenterVMSC

VLRHLR

MS

GSM-PLMN

SMS /SMS-SC

HLR-flag+ SM-SC Id(s)

MS Detached �• no SMS delivery possible• SMS stored in SM-SC

• flag in VLR & HLR

IMSI Attach �• VLR informs HLR

• HLR requests SM-SC via SMS-GMSC to retransmit SMS

MS Detached �• no SMS delivery possible• SMS stored in SM-SC• flag in VLR & HLR

IMSI Attach �• VLR informs HLR

• HLR requests SM-SC via SMS-GMSC to retransmit SMS

VLR-flag

Fig. 26

38

Chapter 5

Radio Interface

Radio Interface

Radio Interface

Contents

2 Physics of Layer 11 14 Logic of L12 25 MOC / MTC 3

Radio Interface Siemens

1 Physics of Layer 1

Physics of Layer 1

TDMAframe

4.615ms

time

TS4

TS5

TS6

TS7

TS0

TS1

TS2

TS3

Frequency[MHz]

••• •••

Duplex distance: 45 MHz

200 kHz

Example:GSM900

890 915 935 960

UL DL

TS577��s

Physical channel (Um)Physical channel (Um)

Radio Interface (Layer 1)

Fig. 1

2

Siemens Radio Interface

The Radio Interface: Physics of Layer 1

The Layer 1 of Um is described in GSM Rec. 04.04. In the following, L1 is separatedfor didactical reasons in the “Physics of L1” transmission and the “Logic of L1”transmission.

For the transmission of user data / signaling physical channels are allocated to theusers. A physical channel in GSM is defined by a frequency pair for UL/DL and aTime Slot TS of the TDMA frame. The frequency bandwidth in GSM is 200 kHz. ATime Slot TS has a duration of 0.577 ms. 8 TS form a TDMA frame; the duration of aTDMA frame is 4.615 ms.

The Burst

In GSM, using FDMA & TDMA for multiple access, the transmission of data is notcontinuously. In every Time Slot TS the HF has to be switched on, the data aretransmitted briefly and then the HF transmission is switched off again. This type ofHF transmission is called “pulse” or “bursty” operation. Therefore, the content of a TSis called “Burst”.

The transmitter is only allowed to transmit the HF Burst within the duration of the TS.If the HF transmission exceeds the duration of the TS, the transmission mightinterfere with the transmission of the succeeding user. In this case, strongdisturbances of both connections follow. For this reason, the transmission must betimed exactly. Furthermore, it is not possible to switch on / off immediately. Toprevent interference between neighboring TS, the GSM Rec. define a duration duringwhich the switching process must be closed. The BS and MS must be able to switchthe HF power on / off within 0.028 ms over a wide dynamic range. This range is 70dB for BS and 36 dB for MS.

So the burst transmission can be explained as a maximum of 0.028 ms for switchingon HF to the necessary power level, 0.5428 ms for the HF transmission of the so-called “useful part” (corresponding with 147 bit) and 0.028 ms for switching off the HFpower level down to “background noise” level. Note: This “useful part” + flanksexceeds the duration of a TS (0.577 ms) and often irritate readers of GSM literature.The 0.028 ms are however only time maximum limits for the flanks. They carry novaluable information and so they are allowed to interfere with the succeeding Burstsin a negligible way.

3



Power

Time

28 ��s 28 ��s 542,8 ��s

The Burst

„Useful part“„Useful part“

Fig. 2

4


Burst: Content

�� 7 0 1 2 3 4 5 6 7

TBTail Bits

3 bit

“Information”142 bit

TBTail Bits

3 bit

GPGuard Period

8.25 bit

HF transmission

TS = 576 12/13 ��s

= 156.25 bit

1 bit = 3.6923 ��s

Fig. 3

Burst: Content

A Time Slot is defined as a duration of 0.577 ms (to be precise: 0.576923 ms). Thisduration is divided per definition into 156.25 bit. This means an individual bit has aduration of 3692.3 ns.

The 156.25 bit are used / defined as follows:

142 bit for the transmission of “Information” (not only users data / signaling but alsocontrol information necessary for maintenance of the connection)

3 bit as Tail Bits TB for edge limitations of the TS. They are preventing, that usefulinformation are “falling” into the flanks of the burst. TB contain no useful information.They are modulated as content “0”.

8.25 bit as Guard Period GP. The GP is not part of the HF transmission. It is used tocompensate run-time effects in the cells. Note: There is one exception of GPs: Thefirst MS transmissions of the MS toward the network use special bursts (AccessBurst) with an extended GP of 68.25 bit.

5


TB Information-Bits STraining

SequenceS TB GPInformation-Bits

156.25 Bit = 576.9 ��s

3 57 1 26 1 57 3 8.25

Normal Burst 5 Burst Typeswith different logical content(discussed later-on)

5 Burst Typeswith different logical content(discussed later-on)

Example:

Normal Burst

Bit

S: Stealing flagTB: Tail BitsGP: Guard Period

142 bit “Information”

Fig. 4

Example: Normal Burst NB

The Normal Burst is part of the “Logic of Layer 1” and will be explained together withthe four other Burst Types later-on in detail. It is shown here for didactical reasons toget an idea of the content of what has been determined as “Information”.

The 142 bit of “Information” (content: “0” or “1”) are realized in the middle of the burstto enable reliable transmission. The 3 TB (content: “0”) on the edge provide bufferagainst data loss at the flanks of the burst.

The Normal Burst NB contains:

� 2 x 3 bit as Tail Bits TB

� 2 x 57 bit as Information (User Data / Signaling)

� 2 x 1 bit as “Stealing Flags” which inform the receiving side if user data or userrelated signaling is transmitted

� 26 bit as Training Sequence for time synchronization and transmission qualityanalysis

Now the structure of a TS / burst is explained, the content has been described downto bit level, but the question is now:

How are the “0” and “1” physically presented on the radio interface?

6


1

0

fT - f

fT + f

fT

+ 180°

+ 90°

t

- 180°

- 90°

phase

binary

signal

frequency

Minimum Shift

Keying MSK

GMSK: Gaussian MSKMSK signal x Gaussian curve

� smaller band-width

Fig. 5

GSM Modulation: Gaussian Minimum Shift Keying

For transmission of the binary data “0” and “1” in GSM a frequency modulationmethod has been chosen. It is known as Gaussian Minimum Shift Keying GMSK.

Minimum Shift Keying MSK

The GMSK is based on Minimum Shift Keying MSK. MSK is a modulation principle,where the information is transmitted in the instantaneous frequency of the HF signal.

The carrier frequency fT is shifted by the frequency difference �f = 67.7 kHz toindicate "1" or "0". This is achieved not by shifting the frequency directly, but by achange of the phase velocity. This results in a frequency and phase variation.

Gaussian MSK

In GMSK, the phase transitions are smoothed by filtering the data with a gaussiancurve. This enables smooth phase shifts, keeping the bandwidth comparable narrow.Thus, a bandwidth of only 200 kHz can be achieved.

7


Frames

TDMA frames

A single frequency band in TDMA systems is subdivided into several Time Slots TS,which can be used by different users. In GSM 8 TS form one TDMA frame (4.615ms), i.e. 8 physical channels are using the same frequency band being cyclically(every 4.615 ms) allocated to a certain user / application.

So the TDMA frame is a repetition cycle with a duration of 4.615 ms.

The TDMA frames themselves are again part of a repetition cycle of a larger duration.Certain contains are always repeated after a certain duration. This repetition cycle iscalled: Multiframe.

Multiframes

Here a separation has to be done according to the type of information a physicalchannel is transmitting. The physical channels can be used to transmit either userdata or signaling.

Multiframes of physical channels allocated for user traffic (Traffic Channels TCH) arerepetition cycles of 26 TDMA frames.

Multiframes of physical channels allocated for signaling data (mostly on one / severalof the TS0 of the carrier of one cell) are repetition cycles of 51 TDMA frames.

Certain “logical contents” are repeated on certain TDMA frames of the 26 TDMAframes of the TCH Multiframes or on the 51 TDMA frames of the signalingMultiframe.

8



TDMA

frame

Frames

RFC

3

RFC

2

RFC

1

0

1

2

3

4

5

6

70

1

2

3

4

5

20

21

22

23

24

25

43

44

45

46

47

48

49

50Time

RFC

124

Frequency

0

1

2

3

4

5

6

7Time

FDMA

User

Traffic

Signaling

cyclical repetition

of certain contents

cyclical repetition

of certain contents

• TDMA-

• Multi-

• Super-

• Hyper-

Frames

Multi-

Frames

Fig. 6

9


26 TDMA frame = 120 ms

Full Rate (FR) TCH

T/t = TDMA frame for TCH

A/a = TDMA frame for SACCH/T

I = Idle

2 Half Rate (HR) TCH

Example:

TCH Multiframe

T T T T T T T T T T T T A T T T T T T T T T T T T I

T t T t T t T t T t T t A t T t T t T t T t T t T a

Signaling Multiframe

�� Logic of L1

User related control data

to maintain connection

TCH: Traffic Channel

SACCH: Slow Associated Control Channel

Fig. 7

Example: Traffic Channel TCH Multiframe

The TCH Multiframe consists of 26 TDMA frames with user data. Every one of this 26TDMA frames contains a certain “logical content”. So certain contents are repeatedevery 120 ms. This is necessary because the “user data” which are transmitted onthis Traffic Channel are not only the user information (Traffic Channel TCH = userspeech, fax, data) which he likes to transmit. Also user related control information(so-called Slow Associated Control Channel SACCH) which are necessary tomaintain the connection are transmitted on the same physical channel. They aretransmitted every TCH Multiframe, i.e. every 120 ms on the 13th TDMA frame (FullRate TCH), respectively at Half Rate transmission for the first user of this physicalchannel on the 13th and for the second user on the 26th TDMA frame.

In Full Rate transmission the 26th TDMA frame is empty (Idle I).

A general overview and description of the different “logical contents” which aredefined in GSM and the content of the Signaling Multiframes is given later-on in“Logic of L1”.

10


Time Structure of the Radio Interface:

Bit: The shortest unit of the GSM radio interface is one bit. Its information is GMSKmodulated onto the HF. Its duration is 3692.3 ns.

Time Slot TS: The TS consists of 156.25 bit. It is the shortest possible transmissiontime in GSM with a duration of 0.57688 ms.

TDMA frames: 8 TS form 1 TDMA frame with a duration of 4.615 ms. 8 physicalchannels are using the same frequency band being cyclically (every 4.615 ms)allocated to a certain user / application.

Multiframes: The TDMA frames themselves are again part of a repetition cycle of alarger duration, the Multiframe. Certain contains are always repeated after a certainduration. Multiframes for user traffic (Traffic Channels TCH) are repetition cycles of26 TDMA frames with a duration of 120 ms. Multiframes for signaling are repetitioncycles of 51 TDMA frames with a duration of 235.4 ms.

Superframe: The TCH / Signaling Multiframes are summarized in longer repetitioncycles to Superframes. Superframes consist of 51 TCH / 26 Signaling Multiframes. ASuperframe (1326 TDMA frames) is the smallest common multiple of TCH andsignaling Multiframes with a duration of 6.12 s.

Hyperframe: The Hyperframe is the GSM numbering period. It comprises 2048Superframes and is exactly 12,533.76 s or 3 h 28 min 56.76 s long. It is a multiple ofall cycles described up to now and determines all transmission cycles / periods onthe radio interface. The Hyperframe is the shortest cycle for repetition of thefrequency hopping algorithm and for ciphering.

1 Signalling Multiframe =

51 TDMA frames � 235,4 ms

1 TCH Multiframe =

26 TDMA frames = 120 ms

Time

Structure

Hyperframe =

2048 Superframes � 3h 29 min

0 1 2 3 4 5 6 7

0 1 2 3 24 25�� 0 1 2 3 49 50��

0 1 2 3 �� 4950

0 1 2 3 24 25

1 Superframe =

51 x 26

TDMA frames

� 6.12 ms

Numbering Periode.g. repetition of • frequency hopping

• ciphering

Channel organisationscheme

Repetition scheme

for TCH / Signaling

BURST = TS content

1 TDMA frame

= 8 TS = 4,615 ms

1 Burst = 156,25 bit = 576,88 us

(1 bit = 3,6923 us)

Fig. 8 11



Adaptive frame alignment:preventing simultaneous

transmission / receiving

UL/DL shifted by 3 TS

Adaptive frame alignment /

Timing Advance TA

76543210

76543210 DL

UL

Timing Advance TA: compensation of propagation delays

BTS commands MS to transmit earlier:

2 x propagation time MS - BTS

Fig. 9

Adaptive Frame Alignment

In GSM the numbering of the Uplink UL and Downlink DL Time Slots TS is shifted bythree TS against each other. This prevents simultaneous transmission and receptionin GSM and enables to create simpler and cheaper Mobile Stations MS. Narrowbandfilters are not necessary. This enabled to built GSM handhelds directly fromcommercial start of GSM in the early 90th.

Timing Advance TA

The Guard Periods GP of the Normal Bursts are not able to compensate signaldelays in larger GSM cells. The MS receives synchronization signals from the BS,synchronizes their transmission based on this signals, but it cannot recognize itsdistance from the BS. The distance can be up to 35 km in a normal GSM cell. Atransmission without special compensation of this run-time delay would result ininterference with the succeeding TS.

Therefore, the BS analyses the delay of the MS transmission using the very first MSburst (which has an extended GP). The BS adjusts its transmission in the DL andinforms the MS with the Timing Advance TA information how to adjust the ULtransmission (i.e. how much earlier the transmission has to start). Over the totalconnection, the delay is analyzed by the BS and new TA values set for the MS. 64TA values (difference: plus/minus 1 bit period) can be used to compensate run-timeeffects.

12


Frequency Hopping

Frequency Hopping means to change the frequency used for transmission isconsequently changed every TDMA frame following a certain frequency hoppingalgorithm. The Time Slot of the physical channel is still fixed.

The logic behind frequency hopping is to guarantee that all channels have the samehigh degree of transmission quality by dividing possible short term interference overall channels of the cell.

So a narrow-band interference does not disrupt the total transmission on one carrier,i.e. on one frequency band, because the transmission is hopping from TDMA frameto TDMA frame to other frequencies.

Nevertheless, now interference occurs for all the carrier of the cell from time to timewhen transmitting on the disturbed frequency band. But this can be compensated inGSM, because in classical GSM there is always redundancy on the transmitted data.The redundant information is delivered in the next TS of the succeeding TDMAframe, i.e. on another frequency (which is not disturbed).

Frequency hopping is optional in GSM. It is on the PLMN operators decision to usefrequency hopping or not. Frequency hopping significantly improves the quality /reliability of transmission.

The carrier transmitting the Broadcast Control Channel BCCH (carrying informationnecessary for MS synchronization to the network) does not participate in frequencyhopping.

Frequency hopping is done in the MS and BS, managed from the BSC. Thefrequency hopping algorithm can be configured from an OMC.

Frequency Hopping

frame 0 frame 1 frame 2 frame 3 frame 4 frame 5

RFC 1

RFC2

RFC 3

RFC 4

RFC 5

TCH

Compensation of

narrow-band interference

� stable & reliable transmission(redundant bits on different TDMA frames)

Fig. 10 13



2 Logic of L1

Signaling

Traffic

User Data

DL

DL

UL

UL + DL

DL

UL+

BCCH

FCCH

SCH

PCH

AGCH

RACH

SDCCH

SACCH

FACCH

TCH/F

TCH/H

BCHBroadcast Channel

CCCHCommon Control

Channel

DCCHDedicated Control

Channel

Logic of L1


Fig. 11

14


Logical Channels

Different signaling and user data contents determine different Logical Channels inGSM.

For user data transmission two different Logical Channels are used:

� TCH/F Traffic Channels, Full rate (FR/EFR speech: 13 / 12.2 kbit/s; data: 9.6kbit/s)

� TCH/H Traffic Channels, Half rate (HR speech: 5.6 kbit/s; data: 4.8/2.4/1.2/0.6/0.3kbit/s)

For signaling 3 types of Logical Channels are used: BCHs, CCCHs and DCCHs.

Broadcast Channels BCH are used DL only for MS synchronization & information:

� FCCH Frequency Correction Channel: for MS frequency synchronization

� SCH Synchronization Channel: for MS time synchronization; contains additionallyTDMA frame no., BSIC

� BCCH Broadcast Control Channel: contains system & cell parameters, e.g. CGI(i.e. PLMN, LAI), channel combining, frequency hopping algorithm, cipher mode,cell capabilities: e.g. EFR/FR/HR, VAD/DTX, ASCI, HSCSD, GPRS, EDGE,..)

Common Control Channels CCCH are used uni-directional UL & DL for initialaccess:

� PCH Paging Channel: to search the MS in the LAI in case of an MTC

� RACH Random Access Channel: MS request for dedicated signaling resources

� AGCH Access Grant Channel: to grant a dedicated channel to the MS

Dedicated Control Channels DCCH are used bi-directional for dedicated signaling:

� SDCCH Stand-alone Dedicated Control Channel: dedicated signaling between MS& BS for Call Setup (Authentication, Cipher start, IMEI check, TMSI-Reallocation,Setup,..) LUP procedures, SMS

� SACCH Slow Associated Control Channel: allocated together with SDCCH orTCH; control information to maintain connection (e.g. DL: Power Control, TimingAdvance, Comfort Noise; UL: Measurement Reports for Handover,..)

� FACCH Fast Associated Control Channel: allocated instead of TCH in case ofenhanced demand for signaling resources (Handover, Call Release, IMSI-Detach,OACSU..)

15



Allocation of signaling channel

Signaling MS � BTSE for e.g. Call Setup (Authentication, Cipher start, IMEI check,Setup info,..) LUP, SMS,...

Signaling

Traffic

User Data

DL

DL

UL

UL + DL

DL

UL+

FCCH

SCH

PCH

AGCH

SDCCH

SACCH

FACCH

TCH/F

TCH/H

Frequency synchronization

Time synchronization + BSIC, TDMA-No.

Paging / Searching (MTC)

Measurement Report,

TA, PC, cell parameters,...

Signalling instead of TCH(e.g. for HOV, IMSI Detach, Call Release)

BCHBroadcast Channel

CCCHCommon Control

Channel

DCCHDedicated Control

Channel

User data Full Rate

Logical channels

User data Half Rate

BCCH: Broadcast Control Channel

FCCH: Frequency Correction Channel

SCH: Synchronisation Channel

PCH: Paging Channel

AGCH: Access Grant Channel

RACH: Random Access Channel

SDCCH: Stand-alone Dedicated Control Channel

SACCH: Slow Associated Control Channel

FACCH: Fast Associated Control Channel

TCH: Traffic Channel

BCCHCGI, FR/EFR/HR, VAD/DTX, HSCSD,frequency hopping, channel combinations

RACH Request for signaling channel

Fig. 12

16


Burst Types

The HF transmission, which is transmitted in a Time Slot with a pre-defined bitsequence is call Burst. In GSM there are 5 different Burst types defined:

Normal Burst NB: The NB is used for most of the Logical Channels (TCH, BCCH,PCH, AGCH, SDCCH, SACCH, FACCH). It consists of the following bit sequence:

� 2 x 3 bit as Tail Bits TB for edge limitation of the HF burst (content: “0”),

� 2 x 57 bit as Data Bits (Information), which carry the users data or signalinginformation.

� 2 x 1 bit as Stealing Flags S, which indicate whether user data (TCH) or userrelated signaling (FACH) is transmitted in this Burst.

� 26 bit as Training Sequences, which are fixed bit pattern (8 different sequencesexist for NB) for synchronization of the transmitted burst & recognition oftransmission quality

� 8.25 bit as Guard Period GP, which is not part of the HF transmission; used asguard period between succeeding TS.

Frequency Correction Burst: It is used for the FCCH only, consisting of:

� 142 Fixed Bits with content “0”; it is used for MS frequency synchronization

� 2 x 3 bit as Tail Bits

� 8.25 bit Guard Period

Synchronization Burst: It is used for the SCH only, consisting of:

� 64 bit as Training Sequence for initial precise MS time synchronization

� 2 x 39 bit with Information necessary for initial MS access (BSIC, TDMA framenumber, NB training sequence used in this cell,..)

Random Access Burst: It is used for RACH only, consisting of:

� 36 bits Information for initial access (BSIC, MS random no., access reason)

� 41 bits as Synchronization Sequence

� 8 + 3 bits as Tail Bits

� 68.25 bits Guard Period GP; the extended GP prevents interference with thesucceeding TS occurring due to the run-time problem (the MS lacks of informationabout its distance to the BS before starting access)

17



Dummy Burst: The Dummy Burst has NB structure; it is transmitted in special casesif nothing else (useful) is to be transmitted (e.g. at the BCCH carrier, which has to betransmitted continuously because it is the cell beacon).

TB

3bit

Information57 bit

S1bit

Training

Sequence26 bit

S1bit

TB

3bit

GP

8.25bit

Information57 bit

156.25 Bit = 576.9 ��s

Normal Burst TCH, BCCH, PCH, AGCH, SDCCH, SACCH, FACCH

Burst Types

TB

3bit

Fixed bits142 bit

TB

3bit

GP

8.25bit

Frequency Correction Burst: FCCH

TB

3bit

Information39 bit

Training

Sequence64 bit

TB

3bit

GP

8.25bit

Synchronization Burst: SCH

TB

8bit

Synchronization

Sequence41 bit

TB

3bit

GP

68.25bit

Information36 bit

Random Access Burst: RACH

Information39 bit

Dummy Burst: Structure �� Normal Burst

Fig. 13

18


Multiframe: Channel Combinations

There are seven different schemes to co-ordinate the logical channels in multiframes.Three schemes are used for the co-ordination of Full rate and Half rate TrafficChannels. Four schemes are used to co-ordinate signaling, depending on therequirements of the individual cell. The network operator has do decide, whichchannel combinations are used for a cell.

Combination I – III are used for TCH Multiframe co-ordination (Full rate / Half rate).

Combination IV – VII are used for Signaling Multiframe co-ordination.

Combination I: TCH/F + FACCH/F + SACCH/F

Combination I is used to transmit Full rate user data & speech. The frames 0–11and 13-24 are used for user data, frame 12 is used for SACCH (user relatedcontrol data) and frame 25 is not used (I: Idle).

Combination II & III: TCH(0,1) + FACCH/H(0,1) + SACCH/H(0,1) respectivelyTCH/H(0) + FACCH/H(0) + SACCH/H(0) + TCH/H(1) + FACCH/H(1) + SACCH/H(1)

Combination II & III are used to transmit Half rate user data & speech. 2 TCH/Huser have to share the 26 multiframes. Data from user 1 or user 2 are filledalternately into the frames. The SACCH of user 1 is on frame 12, the SACCH ofuser 2 is on frame 25.

Combination IV: FCCH +SCH + CCCH (PCH & AGCH) + BCCH

Combination IV offers much space for the Common Control Channels CCCH.Therefore, this combination is used often for cells with many carrier. As BCCHcarrier it is the cell beacon and so it must be used exactly only on one carrier ofthe cell. It is allocated on TS 0 of this carrier and has to be transmittedcontinuously. If no useful information is to be transmitted, Dummy Bursts have tobe used. There is no Power Control used on the cells beacon. Combination IVlacks of dedicated signaling channels (SDCCH and SACCH). Therefore, it has tobe used together with combination VII.

19



I) TCH/F + FACCH/F + SACCH/F

II) TCH/H(0,1) + FACCH/H(O,1) + SACCH/H(0,1)

III) TCH/H(0) + FACCH/H(0) + SACCH/H(0) +

TCH/H(1) + FACCH/H(1) + SACCH/H(1)

IV) FCCH + SCH + CCCH + BCCH

V) FCCH + SCH + CCCH + BCCH + SDCCH/4 + SACCH/4

VI) CCCH + BCCH

VII) SDCCH/8 + SACCH/8

Multiframe: Channel Combinations

F

0

S

1

BCCH

2 - 5

CCCH

6 - 9

F

10

S

11

CCCH

12 - 19

F

20

S

21

CCCH

22 - 29

F

30

S

31

CCCH

32 - 39

F

40

S

41

CCCH

42 - 49

I

50

F:FCCH

S:SCH

B: BCCH

R

0

R

1

R

10

R

11

R

20

R

21

R

30

R

31

R

40

R

41

R

50

DL

UL

Combination IV

C: CCCH (PCH, AGCH)

I: Idle

R: RACH

TCH-Combinations

shown before

TCH-Combinations

shown before

Fig. 14

20


Combination V: FCCH + SCH + CCCH + BCCH + SDCCH/4 + SACCH/4

Combination V is the minimum configuration for a cell, because is contains alllogical channels necessary for signaling in a cell. It is often used for cells with onlyone or two carrier. For combination V the same is valid as for combination IV: It isthe cell beacon, it must be allocated on TS 0 of exactly one carrier of the cell. Ithas to be transmitted continuously. SDCCH/4 and SACCH/4 means that thiscombination offers the capacity for 4 simultaneous dedicated signalingconnections.

Combination VI: CCCH + BCCH

Combination VI can be used together with combination IV and VII for cells withvery much traffic and many carriers (up to 16 carriers). This means to be anincreased demand for Common Control Channels, which are offered bycombination VI. The multiframe structure of combination VI is similar as thestructure of combination IV, without FCCHs and SCHs. In combination with IV,combination IV is allocated on TS0 on the carrier and VI combinations can beallocated at TS 2 / 4 / 6 depending on the traffic volume of the cell.

Combination VII: SDCCH/8 + SACCH/8

Combination IV and VI offer no dedicated signaling channels. Therefore, they haveto be used together with combination VII. Combination VII offers up to 8simultaneous dedicated signaling channels. Combination VII can be allocated onTS 0 of other carrier than the BCCH carrier. The BCCH indicates the allocation ofcombination VII.

21



Signaling Multiframe: Combination V

F S F S F S IBCCH CCCH CCCH CCCHSDCCH

0SDCCH

1 F SSDCCH

2SDCCH

3 F SSACCH

0SACCH

1

F S F S F S IBCCH CCCH CCCH CCCHSDCCH

0SDCCH

1 F SSDCCH

2SDCCH

3 F SSACCH

2SACCH

3

SDCCH

0SDCCH

1SDCCH

2

SDCCH

0SDCCH

1SDCCH

2

SACCH

2

SACCH

0

SDCCH

3

SDCCH

3

R R

R R

SACCH

3

SACCH

1

RR

RR

R R

R R

R R

R R

R R

R R

R R

R R

R R

R R

R R

R R

R R

R R

R R

R R

R

R

RR

RR

RR

RR

RR

RR

DL: BCCH + CCCH + 4 SDCCH (SDCCH/4) + 4 SACCH (SACCH/4)

UL: CCCH + SDCCH/4 + SACCH/4

ISDCCH

0SDCCH

1SACCH

4SACCH

5

ISDCCH

0SDCCH

1SACCH

0SACCH

1

SDCCH/8 + SACCH/8

UL

Combination VIIDL

SDCCH

2SDCCH

3

SDCCH

2SDCCH

3

SDCCH

4SDCCH

5

SDCCH

4SDCCH

5

SDCCH

6SDCCH

7

SDCCH

6SDCCH

7

SACCH

6SACCH

7

SACCH

2SACCH

3

I

I

I

I

SACCH

5SACCH

6

SACCH

0SACCH

1

SACCH

7

SACCH

2

I

I

I

I

I

I

SDCCH

0SDCCH

1

SDCCH

0SDCCH

1

SDCCH

2SDCCH

3

SDCCH

2SDCCH

3

SDCCH

4SDCCH

5

SDCCH

4SDCCH

5

SDCCH

6SDCCH

7

SDCCH

6SDCCH

7

SACCH

4

SACCH

0

Fig. 15

22


L1 Summary: Physical Channels & GSM Data Rates

GSM uses combined TDMA and FDMA for multiple access.

GMSK has been chosen as modulation principle. The GSM channel bandwidth is 200kHz, the modulation rate 270.833 kbit/s (derived from the GSM frequency normal 13MHz: 13 MHz/48).

According to the GSM TDMA principle chosen with 8 physical channels on onecarrier the total gross data rate for 1 physical channel is 270,833 / 8 = 33,85 kbit/s.

1 physical channel consists of 1 TS (UL/DL) on 1 carrier. 1 TS consists of 156.25 bit.

In the Normal Burst, used for TCH transmission, only 114 bit of these 156.25 bit areinformation bits (user data & user related signaling). Therefore, only 24.7 kbit/s of the33.85 kbit/s are information.

In a TCH Multiframe, only 24 of the 26 frames are filled with TCH, i.e. user data. Theother frames are filled with SACCH (frame 12) or Idle (frame 25). Therefore, the realgross rate of user data in GSM is 22.8 kbit/s.

The net rate in GSM is 13 kbit/s for FR speech, 12.2 kbit/s for EFR, 9.6 kbit/s for datatransmission (+ different other rates for HSCSD and GPRS). The difference betweenthe GSM net rate of user data and the gross rate of 22.8 kbit/s is used for dataredundancy to enable a reliable transmission.

The GSM modulation rate is 270,833 kbit/s. I.e. one single bit has a duration of3692.3 ns.

156.25 bit form one Time Slot TS, i.e. the duration of one TS is 0.5769 ms.

8 TS form one TDMA frame, i.e. the duration of one TDMA frame is 4.615 ms; itcontains 1250 bit.

23



L1 Summary: Physical Channel / GSM Data Rates

TB3

Information57

S1

Training Seq.26

S1

TB3

GP8.25

Information57

0 1 2 3 4 5 6 7

RFC1

RFC2

RFC3

RFCi

RFC123

RFC124

••• •••

UL: 890 MHz 915 MHz

FDMA

GMSK

Modulation200 kHz

270.833kbit/s

TDMA

1 TDMA Frame: 4.615 ms / 1250 bit

1 TS: 33.85 kbit/s

1 Normal Burst: 576.9 �s / 156.25 bit

1 Bit = 3.6923 �s

24.7 kbit/s = 22.8 kbit/s TCH data (incl. redundancy)

+ 0.95 kbit/s SACCH + 0.95 kbit/s “Idle”

Fig. 16

24


3 MOC / MTC

MOC / MTC


RACH: Channel Request

AGCH: Immediate Assign

SDCCH: CM Service Request

SDCCH: Authentication Request

SDCCH: Authentication Response

SDCCH: Cipher Mode Command

SDCCH: Cipher Mode Complete

SDCCH: Setup

SDCCH: Call Proceeding

SDCCH: Assign Command

•••

Fig. 17

25



The MOC is defined as an MS initiated call setup. Several procedures are necessarybetween the MS and the BSS respectively the CN to set up a call. In the following theL1 messages on Um necessary for a “normal” MOC (without Off Air Call SetupOACSU; no emergency call) are shown:

� Channel Request (RACH):MS requests the assignment of a dedicated signalingchannel

� Immediate Assignment (AGCH): the network assigns a dedicated signalingchannel (SDCCH & SACCH). Additionally, a first TA information and PowerControl PC is included.

� CM Service Request (SDCCH): the MS provides information on the requestedservice (Basic Call, Emergency Call, SMS,...) and transmits the subscribersidentity (TMSI / IMSI).

� Authentication Request (SDCCH): the networks checks the real identity (Ki) of theSIM transmitting RAND.

� Authentication Response (SDCCH): the MS answers with the SRES on theAuthentication Request

� Cipher Mode Command (SDCCH): the network commands the MS to startciphering

� Cipher Mode Complete (SDCCH): the MS acknowledges the cipher start (firstciphered message)

� Setup (SDCCH): the MS transmits the Setup information including the desired TS /BS and number of the B-subscriber.

� Call Proceeding (SDCCH): the network acknowledges the authorization for therequested service and confirms the call proceeding.

� Assign Command (SDCCH): a TCH is allocated to the MS

� Assign Complete (FACCH): the MS confirms the TCH allocation (using TCHresources)

� Alerting (FACCH): the network informs the MS on successful call setup (i.e. thephone of the B subscriber rings). This starts generation of the ringing signals in theMS, too.

� Connect (FACCH): the MS is informed, that the B subscriber accepted the call

� Connect Acknowledge (FACCH): the MS confirms the Connect message

� TCH: now network switch over to data transfer; the communication is able to start

26



MOCMobile

Originating

Call








SDCCH: Setup

SDCCH: Call Proceeding


FACCH: Assign Complete

FACCH: Alerting

FACCH: Connect

FACCH: Connection Ackn.

TCH

MS requests for signaling channel

Signalling channel allocation [SDCCH x, TA]

Request MOC (SMS, Emergency Call,..)[TMSI/IMSI]

Request Authentication [RAND]

Authentication Response [SRES]

Start Ciphering [A5-X]

Acknowledgement; 1st ciphered message

Setup Message [Called No.]

Requested Service possible(after subscriber profile check in VLR)

TCH-Allocation [frequency, TS]

Acknowledgement on TCH resource

“Ringing at B-Subscriber”, start ringing signal in MS

“B-Subscriber accept call”

AcknowledgementStart of user data transmission & charging

Fig. 18

27



The basic MOC includes at least 14 messages. As a rule, this signaling requires lessthan 2 s.

Optional further messages are:

IMEI Request, IMEI Response to check the equipment identity

TMSI Reallocation: to allocate a new TMSI to the MS

IMEI check and TMSI reallocation are proceeded after start of ciphering

OACSU:

In case of (TCH) overload on Um OACSU can be used. In this case, the AssignCommand / Assign Complete messages are sent after the Alert message, wasting noTCH resources during this time (only SDCCH resources).

Emergency Call

In case of an Emergency Call, Authentication and Cipher are skipped. Call setup isfaster and allows usage of every Mobile Equipment (even without valid SIM card;IMEI on black list).

MOC Part I & Part II

The two slides MOC Part I & Part II are optional for the TM2100 “GSM Introduction”course. They show the full message flow for a Basic MOC between MS and BSS /NSS, including IMEI check and TMSI reallocation as well as the Call Release.

The SS7 message flow using L4 protocols MAP & BSSAP and L3 Radio Interfacemessages of RR, MM and CM can be used for self-study.

28



MOCPart I

Channel Request CHAN_REQ

MS BSS MSC VLR

ISDN

Immediate Assign IMM_ASS_CMD)

CM Service Request CM_SERV_REQCM_SERV_REQ

Authentication Request AUTH_REQAUTH_REQ

Authentication Response AUTH_RSPAUTH_RSP

Cipher Mode Command CIPH_CMDCIPH_CMD

Cipher Mode Complete CIPH_MOD_COMCIPH_MOD_COM

Check IMEI

TMSI Re-allocation TMSI_REAL_COMTMSI-REAL-CMD

TMSI_REAL_COMTMSI_REAL_COM

SETUP

SETUP

Process Access Request

PROC_ACCESS_REQ

AUTH_RSP

Set Cipher Mode

SET_CIPH_MODE

Forward New TMSI

FORW_NEW_TMSI

TSMI Acknowledged

TMSI_ACK

SEND INFO

EIR

Fig. 19

29


MS BSS MSC VLR

ISDN

Call Proceeding CALL_PROCCALL_PROC

ALERTALERT

MOCPart II

Assign Command ASS_CMDAssign Request ASS_REQ

ASS_COMAssign Complete ASS_COM

Connect CONCON

CON_ACK

Connect Acknowledged CON_ACK

Initial Address Message IAM

Address Complete Message ACM

Answer Message ANM

User data

Release RELREL

DISCDisconnect DISC

Clear Command CLR_CMDRelease phys. Channel CHAN_REL

REL_COMRelease Command REL_COM

Clear Complete CLR_CMPDisconnect DISC

Release REL

Release Complete RLC

Complete Call CALL_CMP

Fig. 20

30


MS requests for signaling channel

Signalling channel allocation [SDCCH x, TA]

Request MOC (SMS, Emergency Call,..)[TMSI/IMSI]

Request Authentication [RAND]

Authentication Response [SRES]

Start Ciphering

Acknowledgement; 1st ciphered message

Setup Message[Bearer Service, Calling No.]

Requested Service possible in MS

TCH-Allocation [frequency, TS]

Acknowledgement (on TCH resource)

“Ringing signal started in MS”

“Mobile subscriber accept call”

AcknowledgementStart of user data transmission & charging

MTCMobile

Terminating

Call








SDCCH: Setup

SDCCH: Call Confirmed


FACCH: Assign Complete

FACCH: Alerting

FACCH: Connect

FACCH: Connection Ackn.

TCH

PCH: Paging Request Searching MS in Location Area

Fig. 21


The MTC is initiated by the network if there is a call for the subscriber. The MTCmessage flow is very similar to the MOC message flow. The most importantdifference on Um is the start. The MS has to paged in all cells of a Location Area LA,using the Paging message.

Paging (PCH): The MS is paged in all LA cells using the TMSI / IMSI.

Setup (SDCCH): Another difference between MTC and MOC is the Setup message.In an MTC it is transmitted from the network to the MS, giving information on therequested service (TS, BS) and the ISDN / MSISDN number of the calling party.

Call Confirmed (SDCCH): After checking its capabilities to support the requestedservice, the MS acknowledges the Setup message with Call Confirmed.

Alerting (FACCH): Different to the MOC, in the MTC the Alerting message istransmitted from the MS to the network, to indicate the start of ringing in the MS.

Connect (FACCH) & Connection Acknowledge: Different to the MOC, in the MTCboth messages have opposite direction, too.

31

Appendix

Appendix

Appendix

Contents

2References1 3 Abbreviations2

Appendix Siemens

1 References

� M. Mouly, M.B. Pautet, "The GSM System for Mobile Communications", Cell & Sys(1992), ISBN 2-9507190-0-7

� S. Redl, M. Weber, K. Oliphant, "An introduction to GSM", Artech House Inc.(1995), ISBN 0-89006-785-6

� A. Mehrotra, "GSM System Engineering", Artech House Inc. (1997), ISBN 0-89006-860-7

� G. Heine, "GSM-Signalisierung", Funkschau: Funktechnik, Franzis-Verlag GmbH(1998), ISBN 3-528-15302

� G. Heine, "GSM Networks: Protocols, Terminology and Implementation", ArtechHouse Inc. (1999), ISBN 0-89006-471-7

� G. Heine, "GPRS from A – Z", Artech House Inc. (2000), ISBN 1-58053-181-4

� G. Heine, "GPRS, EDGE, HSCSD and the Path to 3G", Artech House Inc. (2001),CD-ROM, ISBN 1-58053-275-6

� "System Description D900/D1800 - GSM PLMN" A50016-D1109-V11-2-7618

� "Technical Description D900/D1800 - Switching Subsystem (SSS)" A50016-D1109-V2-1-7618

� "Base Station System (TED-BSS)" A30808-X3247-H10-1-7618

2

Appendix Siemens

2 Abbreviations

AB access burst

AC authentication center

ACCH associated control channel

ACE antenna coupling equipment

ACE-Rx ACE receive side

ACE-Tx ACE transmit side

ACG auxiliary clock generator

ACM address complete message

ACU antenna combining unit

ADC analog to digital converter

AEF additional elementary function

AF audio frequency

AFC automatic frequency control

AGC automatic gain control

AGCH access grant channel

AMA automatic message accounting

AMPC ATM bridge Processor C

ANT-COMB antenna combiner

AoC advice of charge

AP application part

APS application program system

ARFCN absolute radio frequency number

ARQ automatic repeat request

ASN ATM Switching Network

ATB all trunks busy

ATE automatic test equipment

AUC authentication center

AUT(H) authentication

BA BCCH allocation

BAIC barring of all incoming calls

BAOC barring of all outgoing calls

BAP base processor (CP113)

BCC base transceiver station color code

3

Appendix Siemens

BCCH broadcast control channel

BCH broadcast channel

BER bit error rate

BHCA busy hour call attempts

BIC- Roam barring of incoming calls when roaming outside the HPLMN country

BNHO barring all outgoing calls except those to HPLMN

BOIC barring of outgoing international calls

BOIC-exHC barring of outgoing international calls except those directed to theHPLMN

BS base station

BSC base station controller

BSCU base station control unit

BSIC base transceiver station identity code

BSS base station system

BSSAP base station system application part

BSSMAP base station system management application part

BSSOMAP base station system operation and maintenance application part

BSU base station system switch unit

BTS base transceiver station

CA cell allocation

CAS channel associated signaling

CAP call processor (CP113)

CBCH cell broadcast channel

CBS cell broadcast service

CC call control

CC channel coding

CC country code

CCBS completion of calls to busy subscribers

CCC common channel control

CCG central clock generator

CCH control channel

CCITT Comité Consulatif International Téléphonique et Télégraphique

CCNC common channel signaling network control

CCNP common channel signaling network processor

4

Siemens Appendix

CCS7 common channel signaling system No. 7

CCS common channel signaling

CCU channel coding unit

CdPA called party address

CF call forwarding

CFB call forwarding on mobile subscriber busy

CFNRc call forwarding on mobile subscriber not reachable

CFNRy call forwarding on no reply

CFU call forwarding unconditional

CGI cell global identity

CgPA calling party address

CHA component handling

CI cell identity

CIC circuit Identification code

CKSN cipher key sequence number)

CLIP calling line identification

CLIR calling line identification restriction

CMD command

CMY common memory

CNI comfort noise insertion

COLI calling line identification

CoLP connected line identification presentation

CoLR connected line identification restriction

CP call processing

CP coordination processor

CPU central processing unit

CR code receiver

CRC cyclic redundancy check

CT call transfer

CT Craft Terminal

CTC continuity check

CUG closed user group

CW call waiting

DAS digital announcement system

5

Appendix Siemens

Appendix Siemens

DB dummy burts

DBMS data base management system

DCCH dedicated control channel

DCN data communication network

DCP data communication processor

DCS1800 digital communication system

DE digital exchange

DEC digital echo compensator

DEMUX demultiplexer

DHA dialogue handling

DIU digital interface unit

Dm control/data channel

DL down link

DPC destination point code)

DPPC data post processing computer

DPPS data post processing system

DRX discontinuous reception

DSMX digital signal multiplexer

DTAP direct transfer application part

DTMF dual tone multi frequency

DTX discontinuous transmission

EIR equipment identification register

EMML extended man machine language

ERP effective radiated power

EWSD Digitales Elektronisches Wählsystem

FAC final assembly code

FACCH fast associated control channel

FACCH/F full rate FACCH

FACCH/H half rate FACCH

FB frequency correction burst

FC filter coupler

FCCH frequency correction channel

FDMA frequency division multiple access

FEC forward error correction)

6

Siemens Appendix

FHE frequency hopping equipment

FN frame number

FPLMTS future public land mobile telecommunication system (CCITT)

GCR Group Call Register

GMSC gateway MSC

GMSK gaussian minimum shift keying

GOS grade of service

GP guard period

GP group processor

GSM Global System for Mobile communications

GSM PLMN GSM public land mobile network

HANDO handover

HC hard copy

HF history file

HLR home location register

HLR-ID home location register identity

HMSC home MSC

HO HANDO

HOLD call hold

HPA high power amplifier

HPLMN home PLMN

HSN hopping sequence number

IAM initial address message

ICB incoming calls barred

ID identification

ID identity

IMEI international mobile equipment identity

IMN installation manual

IMSI international mobile subscriber identity

IMT-2000 International Mobile Telecommunications

IN intelligent network

IOC input/output controller

IOP input/output processor

IOP: AUC input/output processor for the authentication center

7

Appendix Siemens

Appendix Siemens

ISC international switching center

ISDN integrated services digital network

ISUP OSDN user part

IWE interworking equipment

IWF interworking function

IWUP interworking user part

Kc cipher key (ciphering key)

Ki individual subscriber authentication key

LA location area

LAC Location area code

LAI location area identity

LAN local area network

LAPDm link access protocol on the Dm channel

LE local exchange

LIC Line Interface Circuit

Lm TCH with capacity lower than Bm

LMSI local mobile station identity

LMT local maintenance terminal

LR location register

LTG line/trunk group

MA mobile allocation

MAP mobile application part

MAH mobile access hunting

MB message buffer

MBG message buffer group

MBU message buffer unit

MCC mobile country code)

MCI malicious call identification

ME mobile equipment

MFC multifrequency code

MGT mobile global title

MIB management information base

MM mobility management

MMI man machine interface

8

Siemens Appendix

MMI man machine interpreter

MMN maintenance manual

MML man machine language

MNAP management network access point

MNC mobile network code

MOC mobile originating call

MP Main Processor

MPTY multi party service

MPU Main Processor Unit

MS mobile station

MS mobile subscriber

MSC mobile services switching center

MSIN mobile subscriber identification number

MSISDN mobile station international ISDN number

MSRN mobile station roaming number

MT mobile termination

MTC mobile termination call

MTE mobile termination equipment

MTP message transfer part

NB normal burst

NCC network color code (PLMN color code)

NDC national destination code

NE network entity, network element

NEF network element function

NF network function

NI national Indicator)

NM network management

NMC network management center

NMSI national mobile station identification

O&M operation and maintenance

OACSU off air call set up

OCB outgoing calls barred

ODAGEN office date area generator

OMAP operation & maintenance application part

9

Appendix Siemens

Appendix Siemens

OMC operation & maintenance center

OMC- B operation & maintenance center for BSS

OMC- S operation & maintenance center for SSS

OMP operation & maintenance processor

OMP- B operation & maintenance processor for BSS

OMP- S operation & maintenance processor for SSS

OMS operation & maintenance subsystem

OMT operation & maintenance terminal

OMT- B operation & maintenance terminal for BSS

OMT- S operation & maintenance terminal for SSS

OPC originating point code

PA power Amplifier

PCH paging channel

PCM pulse code modulation

PCM- INT PCM interface

PCS personalization center for SIM

PDN public data network

PIN personal identification number

PLMN public land mobile network

PM performance management

PSPDN packet switched public data network

PSTN public switched telephone network

PSU power supply unit

QA Q (interface adapter)

QOS quality of service

RA rate adaptation

RAB random access burst

RACH random access channel

RAE recorded announcement equipment

RAND random number

REC recommendation

REQ request

RES response

RF radio frequency

10

Siemens Appendix

RFC radio frequency channel

RFCH radio frequency channel

RFCN radio frequency channel number

RFM radio frequency management

RFN reduced TDMA frame number

RLP radio link protocol

RMA regional maintenance area

RMC regional maintenance center

ROI remote operation interface

ROSE remote operation service element

RPE- LTP regular pulse excited long term prediction

RR radio resource management

RSE radio system entity

RSS radio subsystem

RT radio terminal

RX or Rx receiver

RXLEV received signal level

RxMC receiver multicoupler

RXQUAL received signal quality

SACCH Slow Associated Control Channel

SACCH/T slow, TCH- associated control channel

SACCH/TF slow, TCH/FS- associated control channel

SACCH/TH slow, TCH/HS associated control channel

SAP service access point

SAPI service access point indicator

SB synchronization burst

SC Switch Commander

SCCP signaling connection control part

SCF Signaling Control Function

SCP Signaling Control Point

SCH synchronization channel

SCN sub- channel number

SCP service control point (IN)

SDCCH standalone dedicated control channel

11

Appendix Siemens

Appendix Siemens

SFH slow frequency hopping

SG safeguarding

SGC switch group control

SGL service guidelines

SI service indicator

SIM subscriber identity module

SM security management

SMC submultiplex channel

SMG Special Mobile Group

SMS service management system

SN subscriber number

SN switching network

SNR serial number

SP signaling point

SPC signaling point code

SPC stored program control

SRES signed response

SSF Signaling Switching Function

SSG space stage group

SSM space stage module

SSNC Signaling System Network Control

SSP Service Switching Point

SSS switching subsystem

STP signaling transfer point

SW software

SYP system panel

SYPC system panel control

SYPD system panel display

TA Terminal Adaptation

TAC Type Approval Code

TAC technical assistance center

TB tail bit

TC transaction capability

TCAP transaction capability Part

12

Siemens Appendix

TCB transcoder board

TCG transcoder group

TCGQ transcoder group quartet

TCH traffic channel

TCH/F full rate traffic channel

TCH/FS TCH full rate speech

TCH/H half rate traffic channel

TCH/HS TCH half rate speech

TDMA time division multiple access

TE terminal equipment

TETRA Terrestrial Trunked Radio Access

THA transaction handling

TMN telecommunication management network

TMRP tower mounted receiver preamplifier

TMS telecommunication management system

TMS test mobile station

TMSI temporary mobile subscriber identity

TN telecommunication network

TN timeslot number

TRAU transcoding and rate adaptation unit

TRX transceiver

TS tele service

TS timeslot

TSM time stage module

TSG time stage group

TUP telephony user part

TX or Tx transmitter

UL uplink

UMTS universal mobile telecommunication system

UP user part

UUS user to user signaling

VAD Voice Activity Detection

VBR Variable Bit Rate

VE exchange equipment

13

Appendix Siemens

Appendix Siemens

VBS Voice Broadcast Service

VGCS Voice Group Call Services

VHE Virtual Home Environment

VLR Visitor Location Register

VMSC Visited MSC

VoIP Voice over IP

VPLMN Visited PLMN

WAN Wide Area Network

WAP Wireless Application Protocol

WARC World Administrative Radio Conference

WLL Wireless Local Loop

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14



Sub-sections CDMA Overview

The way to CDMA Technology 1

Basic Concept of Spread Spectrum Technology 2

CDMA codes and its usage 3

CDMA Air Interface Overview 4

CDMA System Aspects 5

Appindex 6

Reference 7

Glossary 8

CDMA Overview


Sub-section identification Pages1 The Way to CDMA Technology 1 - 392 Basic Concept of Spread Spectrum Technology 1 - 163 CDMA codes and its usage 1 - 204 CDMA Air Interface Overview 1 - 185 CDMA System Aspects 1 - 156 Appendix 1 - 117 References 1 - 2 8 Glossary 1 - 5


Chapter 1

The Way to CDMA Technology

The Way to CDMA Technology

Contents 1 1.1 1.2 1.3 2 2.1 2.2 3 3.1 3.2 4 4.1 5 5.1 5.2 6 6.1 6.2 7 7.1 7.2 7.2.1 7.2.1.1 7.2.2 7.2.2.1 7.2.3 8 8.1

Introduction to Cellular Technology Progress in Radio Communications The Growth in Cellular Market & its demands Why is it called cellular? Advantages of Digital Communications Digital Communication Digital Mobile Systems Cellular System Architecture System Architecture Types of cells Cellular System Components Cellular System Components Wireless Digital Transmission Problems Reasons leading to Wireless Digital Transmission Problems

Result of Wireless Digital Transmission Problems Solutions against Air transmission Problems Solutions for Wireless Digital Transmission Problems Solutions for Bit Error Rate

Transmission Principles Duplex Transmission Multiple Access Techniques Frequency Division Multiple Access The Advanced Mobile Phone Service (AMPS) Time Division Multiple Access The GSM network Code Division Multiple Access Data Transmission Data Transmission Development

2 2 4 6

8 8 10 11 11 13 15 15 17 17 19 21 21 23 24 24 26 26 28 29 31 36 38 38

The Way To CDMA Technology

1

1.1 Progress in Radio Communications

The quest to know the unknown and see the unseen is inherent in human nature.

It is this restlessness that has propelled mankind to ever-higher pinnacles and ever-deeper depths. This insatiable desire led to the discovery of light as being electromagnetic, paving the way to discovery of the radio.

The origin of radio can be traced back to the year 1680 to Newton theory of composition of white light of various colors. This theory brought the importance as light as an area of study to the attention of many scientists, especially those in Europe, who began to pursue experiments with light which lead to importantdiscoveries connected to the eventual development of the radio.

These discoveries are the foundation of today’s wireless cimmunicaton systems. Experiments with light are still being carried out today in many universities, and industries. One of the outcomes of light experiments in the 1970s is the optical fiber, which is currently being used for long – haul voice and data transmission. It is believed that the use of optical fiber technology will increase dramatically the introduction of wideband networks for voice, data, and video transmission, which is based on the Asynchronous Transfer Mode (ATM) switch.

Radio connections were first used for Wireless Communications in the late 19th century; information was sent via "ether" as follows:

1 Introduction to Cellular Technology


2

Progress in Radio communications

1873 Electromagnetic wave theory by J.C. Maxwell

1887 Experimental proof of the existence of electromagnetic waves by H. Hertz

1895 First receiver with antenna for weather reports by A. Popow

1895 First wireless transmission using spark inductor generated by G. M. Marconi

1897 Marconi Wireless Telegraphy Company founded

1901 First transatlantic transmission by Marconi

1909 First radio broadcast at New York, Caruso

1917 First mobile transmission, BS - train

1952 Usage of Analogue Mobile Systems in USA and Europe

1978 CEPT reserved 2x25MHz for GSM

1992 Commercial use of GSM

Fig.1


3

1.2 The Growth in Cellular Market & its demands

The cellular telephone industry has enjoyed phenomenal growth since its inception in 1983. In just one more example of the impossibility of projecting the adoption of new technologies, a widely accepted 1985 prediction held that the total number of cellular subscribers might reach as many as 900,000 by the year 2000. In fact, by the end of 1994 there were well over 20 million subscribers in the United States alone, and approximately 50 million worldwide. Recent annual subscriber growth rates have been as high as 40%, and it is believed that this growth rate could continue through the rest of the 1990s.

In order to meet this increasing demand for service, new digital cellular telephone systems have been introduced during the first half of the 1990s. As today's cellular operators move to adopt these new technologies in their systems, they demand:

l Increased capacity within their existing spectrum allocation and easy

deployment of any technology it takes to get them that capacity increase. l Higher capacities and lower system design costs (plus lower infrastructure

costs) which will lead to a lower cost per subscriber. l A lower cost per subscriber combined with new subscriber features, which

will help the operators to increase their market penetration. l An increased market penetration, which will lead to an increase in number of

subscribers and a system, which offers support for that, increased capacity. l High quality calls must be maintained during the change to or migration to any

new digital technology.


4

Avdantages of cellular communications

Fig.2

• lower cost per subscriber • Increased market penetration • Higher capacities • lower system design costs


5

1.3 Why is it called cellular? Everyone is familiar with the usage of the term “cellular” in describing mobile radio

systems. You probably know that it is called cellular because the network is composed of a number of cells. Mobile radio systems work on the basis of cells for two reasons.

The first reason is that radio signals at the frequencies used for cellular travel only a few kilometers (kms) from the point at which they are transmitted.

They travel more or less equal distances in all directions; hence, if one transmitter is viewed in isolation, the area around it where a radio signal can be received is typically approximately circular. If the network designer wants to cover a large area, then he must have a number of transmitters positioned so that when one gets to the edge of the first cell there is a second cell overlapping slightly, providing radio signal. Hence the construction of the network is a series of approximately circular cells.

The second reason has to do with the availability of something called radio spectrum. Simply, radio spectrum is what radio signals use to travel through space.

Using a mobile radio system, it consumes a certain amount of radio spectrum for the duration of the call. An analogy here is car parks. When you park your car in a car park it takes up a parking space. When you leave the car park, the space becomes free for someone else to use. The number of spaces in the car park is strictly limited and when there are as many cars as there are spaces nobody else can use the car park until someone leaves.

Radio spectrum in any particular cell is rather like this. However, there is an important difference. Once you move far enough away from the first cell, the radio signal will have become much weaker and so the same bit of radio spectrum can be reused in another cell without the two interfering with each other. By this means, the same bit of radio spectrum can be reused several times around the country. So splitting the network into a number of small cells increases the number of users who can make telephone calls around the country.

So, in summary, cellular radio systems are often called “cellular” because the network is composed of a number of cells, each with radius of a few kilometers, spread across the country. This is necessary because the radio signal does not travel long distances from the transmitter, but it is also desirable because it allows the radio frequency to be reused, thus increasing the capacity of the network.


6

Fig. 3


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2.1 Digital Communication

First of all we can say that a digital communication system is one where the voice signal has been digitized prior to wireless transmission.

Digitizing is aprocess where the voice signal is sampled and discrete, numiric representation of the signal are transmitted ,rather than the original signal itself.

This is much different from analog systems where the original,continuous voice signal is transmitted using a standard form of FM modulation.

As the term „Digital“ implies, the voice signal is digitized for transmission within the cellular networks.Once digitized, Advanced coding , transmission,and error correction techniques are employed. These additional techniques make it possible to detect and correct transmission errors at the receiving end.

Another advantage of digital wireless communications is that digital provides more traffic capacity per given RF spectrum. This is made possible by using the channel bandwidth more efficiently .

In digital systems, multible users occupy the same frequency, and they are separated by time or codes. This is more efficient than assigning each user to a separate frequency , which is efficient than assigning each user to a separate frequency, which is common in analog systems.

Digital systems also use techniques to reduce, or compress the amount of information to be transmitted over the air from each user.

These compression techniques can take advantage of the probability that not every user needs maximum bandwidth at exactly the same moment.

Another advantage of digital communication system is that they have ah inherent level of security . Unothorized listeners must have complex receivers, they must decode the digital information, and then they must convert the digital signal into analog signal.

Digital has better built-in support for non-voice services and user data traffic.

By bypassing the voice signal compression process, user data can be processed directly in their digital formats.

With digital systems, there is no need to convert the signal. The data is simply passed through as digital information. This digital information can usually be processed through the system at higher speeds.

Lastly , Analog sytems, on the other hand, use much simpler transmission techniques, which require a receiver no more complex than an inexpensive FM radio.

2 Advantages of Digital Communications


8

Avdantages of digital communications

Fig. 4

Fig. 5

• Security • Higher capacities • Easily Maintainance • Minaturization an friendleness • High Quality with low cost • Worlwide Availability • New Service Implementation • High Fidility

Distance to BS

Signal Quality Digital Signal

AnalogueSignal

Transmission Quality:

“Easy to regenerate”


9

2.2 Digital Mobile System

As demand for mobile telephone service has increased, service providers found that basic engineering assumptions borrowed from wireline (landline) networks did not hold true in mobile systems and the early analogue systems quickly became saturated, and the quality of service decreased rapidly.

The components of a typical digital cellular system is shown in fig.. The advantages of digital cellular technologies over analog cellular networks

include increased capacity and security. Technology options such as TDMA and CDMA offer more channels in the same analog cellular bandwidth and encrypted voice and data.

Fig.6


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3.1 System Architecture

Increases in demand and the poor quality of old service led mobile service providers to research ways to improve the quality of service and to support more users in their systems. Because the amount of frequency spectrum available for mobile cellular use was limited, efficient use of the required frequencies was needed for mobile cellular coverage. In modern cellular telephony, rural and urban regions are divided into areas according to specific provisioning guidelines.

Deployment parameters, such as amount of cell-splitting and cell sizes, are determined by engineers experienced in cellular system architecture.

Provisioning for each region is planned according to an engineering plan that includes cells, clusters, frequency reuse, and handovers.

• Cells and Cell Splitting

A cell is the basic geographic unit of a cellular system.The term cellular comes from the honeycomb shape of the areas into which a coverage region is divided. Cells are base stations transmitting over small geographic areas that are represented as hexagons. Each cell size varies depending on the landscape. Because of constraints imposed by natural terrain and man-made structures, the true shape of cells is not a perfect hexagon.

Unfortunately, economic considerations made the concept of creating full systems with many small areas impractical. To overcome this difficulty, system operators developed the idea of splitting cells into sectors to form sector cells.

• Clusters

A cluster is a group of cells in which all available frequencies have been used once. No channels are reused within a cluster.

• Frequency Reuse

The concept of frequency reuse is based on assigning to each cell a group of radio channels used within a small geographic area. Cells are assigned a group of channels that is completely different from neighboring cells. The coverage area of cells are called the footprint. This footprint is limited by a boundary so that the same group of channels can be used in different cells that are far enough away from each other so that their frequencies do not interfere.Cells with the same number have the same set of frequencies.

3 Cellular System Architecture


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Cluster

Fig.7

Fig.8


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3.2 Types of cells

Different types of cells are used due to the density variation of population.

• Macrocells The macrocells are large cells for remote and sparsely populated areas.

• Microcells These cells are used for densely populated areas. By splitting the existing areas

into smaller cells, the number of channels available is increased as well as the capacity of the cells. The power level of the transmitters used in these cells is then decreased, reducing the possibility of interference between neighboring cells.

• Selective cells It is not always useful to define a cell with a full coverage of 360 degrees. In some

cases, cells with a particular shape and coverage are needed. These cells are called selective cells.

A typical example of selective cells is the cells that may be located at the entrances of tunnels where coverage of 360 degrees is not needed. In this case, a selective cell with coverage of 120 degrees is used.

• Umbrella cells A freeway crossing very small cells produces an important number of handovers

among the different small neighboring cells. In order to solve this problem, the concept of umbrella cells is introduced. An umbrella cell covers several microcells. The power level inside an umbrella cell is increased comparing to the power levels used in the microcells that form the umbrella cell. When the speed of the mobile is too high, the mobile is handed off to the umbrella cell. The mobile will then stay longer in the same cell (in this case the umbrella cell). This will reduce the number of handovers and the work of the network .A too important number of handover demands and the propagation characteristics of a mobile can help to detect its high speed.

• Handoff The final obstacle in the development of the cellular network involved the problem

created when a mobile subscriber traveled from one cell to another during a call. As adjacent areas do not use the same radio channels, a call must either be dropped or transferred from one radio channel to another when a user crosses the line between adjacent cells. Because dropping the call is unacceptable, the process of handoff was created. Handoff occurs when the mobile telephone network automatically transfers a call from radio channel to radio channel as a mobile crosses adjacent cells.

During a call, When the mobile unit moves out of the coverage area of a given cell site, the reception becomes weak. At this point, the cell site in use requests a handoff. The system switches the call to a stronger frequency channel in a new site and the call continues as long as the user is talking, and the user does not notice the handoff at all.


13

Fig.9

Fig.10

Fig.11


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4.1 Cellular System Components

The cellular system offers mobile and portable telephone stations the same service provided fixed stations over conventional wired loops. It has the capacity to serve tens of thousands of subscribers in a major metropolitan area. The cellular communications system consists of the following four major components that work together to provide mobile service to subscribers: 1. Mobile telephone switching office (MTSO)

2. Cell site with antenna system 3. Mobile Station (MS)

• Mobile Telephone Switching Office (MTSO) The MTSO is the central office for mobile switching. It houses the mobile switching

center (MSC), field monitoring and relay stations for switching calls from cell sites to wireline central offices (PSTN).

• The Cell Site

The term cell site is used to refer to the physical location of radio equipments that provide coverage within a cell. A list of hardware located at a cell site includes power sources, interface equipment, radio frequency transmitters and receivers, and antenna systems.

• Mobile Station (MS)

The mobile subscriber unit consists of a control unit and a transceiver that transmits and receives radio transmissions to and from a cell site. Three types of MSUs are available: 1. The mobile telephone (typical transmit power is 4.0 watts) 2. The portable (typical transmit power is 0.6 watts)

3. The transportable (typical transmit power is 1.6 watts) The mobile telephone is installed in the trunk of a car, and the handset is installed

in a convenient location to the driver. Portable and transportable telephones are hand held and can be used anywhere. The use of portable and transportable telephones is limited to the charge life of the internal battery.

4 Cellular System Components


15

Fig.12


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5.1 Reasons leading to Wireless Digital Transmission Problems Wireless communication channels suffer from severe attenuation and signal

fluctuations and this is mainly due to three important reasons which are:

1. Velocity of Mobile Station within the area of the Base Tranciever Station. 2. Distance between Mobile Station and the Base Tranciever Station. 3. Obstacles between the Mobile Station and the Base Tranciever Station. Large attenuation is due to the user’s mobility through the propagation

environment that causes almost no direct signal from the transmitter can reach the receiver. Even if so, the line-of-sight signal may be superimposed by its reflected or scattered duplicates that reach the receiver at different time instant causing signal fluctuations. When a mobile station moves from one location to another, all propagation scenario may change completely and the received signal changes accordingly. Three different models that are commonly used to characterise a wireless channel are:

• Propagation path loss (near-far attenuation) .

• Shadowing (variation on the average power) .

• Multipath fading (fast signal fluctuation).

• Propagation path loss It occurs when the received signal becomes weaker and weaker due to

increasing distance between MS and BTS . Path loss is proportional to the square of the distance and the square of the transmitted frequency .

• Shadowing

It is due to obstacles being between the MS and the BTS , like buildings, hills etc. When the MS moves around , the signal fluctuates normally around a mean value depending on the obstacles.

• Multipath fading It occures when there is more than one transmission path to the MS or BTS ,

and therefore more than one signal is arriving at the receiver .This may be due to buildings or mountains , either close to or far from the reciving device,Rayleigh fading and time dispersion are forms of multipath fading.

1. Rayleigh fading It occures when the signal takes more than one path between the MS and BTS. Rayleigh fading occurs when the obstacles are near to the receiving antenna

2. Time dispersion

It contrasts to Rayleigh fading , the reflected signal comes from an object far away from the receiving antenna .Since the bit rate on the air is 270 kbit/sec,one bit corresponds to 3.7 µ sec or 1.1 km . If an obstacle is further than 500 m away, then the reflected bit will interfere with the next transmitted bit (ISI).

5 Wireless Digital Transmission Problems


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Fig.13

Fig.14


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5.2 Result of Wireless Digital Transmission Problems

• Bit Error Rate

Sometimes, when you are using a mobile phone, you will notice that the speech quality “breaks up” or disappears completely for short periods of time. By moving toward a window you can sometimes improve the situation. This loss of speech quality is caused by errors. That means, the transmitter might send 1011, but because of propagation problems, such as fast fading, the receiver gets 1001.The third bit is said to be in error. This is a little like spelling something over the phone.You might say “S” but the person at the other end might respond “was that F?” An error was made because the line was not of sufficient quality. Mobile phones contain advanced systems for correcting errors but However, these systems are not always able to remove all the errors. Without error correction, the speech quality would always be so terrible that you would never be able to understand the other person.

Interference, fading, and random noise cause errors to be received, the level of which will depend on the severity of the interference. The presence of errors can cause problems. For speech coders such as ADPCM (Adaptive Defrential PCM), if the bit error rate (BER) rises above 10-3 (that is, 1 bit in every 1000 is in error, or the error rate is 0.1%) then the speech quality becomes unacceptable.

For near-perfect voice quality, error rates of the order of 10-6 are required. For data transfers, users expect much better error rates, for example on computer files, error rates higher than 10-9 are normally unacceptable.

If the only source of error on the channel was random noise, then it would be possible, and generally efficient, to simply ensure that the received signal power was sufficient to achieve the required error performance without any need for error correction. However, where fast fading is present, fades can be momentarily as deep as 40 dB. To increase the received power by 40 dB to overcome such fades would be highly inefficient, resulting in a significantly reduced range and increased interference to other cells. Instead, error correction coding accepts that bits will be received in error during fades but attempts to correct these using extra bits (“redundant” bits) added to the signal.


19

Fig.15


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6.1 Solutions for Wireless Digital Transmission Problems

• Antenna Diversity

It increases the received signal strength by taking advantage of the nature properties of radio waves , there are two diversity methods, they are :-

1. Space diversity .

2. Polarization diversity .

♦ Space diversity can be achieved by mounting two receivers instead of one . If the two receivers

are physically separated , the probability that both of them are affected by a deep fading dip at the same time is low .

♦ Polarization diversity With this technique the two space diversity receivers are replased by one dual

polarized antenna , the antenna contains two differently polarized antenna arrays.

• Time Advance

Time Advance is introduced to overcome the effect of time alignment. When the MS is moving far away from the BTS , this BTS tells the MS how much time ahead of the synchronization time it must transmit the burst .

6 Solutions of Air transmission problems


21

Fig.16

Fig.17


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6.2 Solutions for Bit Error Rate

• Channel Coding

Error correction is widely deployed in mobile radio, where fast fading is almost universally present. Error correction systems all work by adding redundancy to the transmitted signal. The receiver checks that the redundant information is as it would have expected and, if not, can make error correction decisions. In an error detection scheme, the receiver requests that the block that was detected to be in error is retransmitted. Such schemes are called automatic request repeat (ARQ).Some of the more advanced coding systems can perform error correction and also detect if there were too many errors for it to be possible to correct them all and hence request retransmission in this case.

• Interleaving

Signals traveling through a mobile communication channel are susceptible to fading. The error-correcting codes are designed to combat errors resulting from fades and, at the same time, keep the signal power at a reasonable level. Most error-correcting codes perform well in correcting random errors. However, during periods of deep fades, long streams of successive or burst errors may render the error-correcting function useless. Interleaving is a technique for randomizing the bits in a message stream so that burst errors introduced by the channel can be converted to random errors.

Fig.18


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7.1 Duplex Transmission

• FDD and TDD

Two duplex methods are used for coordinating the uplink (UL) and downlink (DL) components of a transmission between a base station and a mobile station, namely Frequency Division Duplex (FDD) and Time Division Duplex (TDD).

UL and DL are implemented for FDD in different frequency bands. The gap between the two frequency bands for UL and DL is known as the duplex distance. It is constant for all mobile stations in a standard. Generally the DL frequency band is positioned at the higher frequency than the UL band.

In the case of TDD, UL and DL are implemented in the same frequency band, Uplink (UL) and Downlink (DL) takes place at different times. There is fast switching between UL and DL transmission, so that the user has the impression of simultaneous transmission and reception.

As a result, only a fraction of the time needed for analog transmission is required for digital transmission of subscriber data.

7 Transmission Principles


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Fig.19

Fig.20


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7.2 Multiple Access Techniques

Wireless telecommunications has drastic increase in popularity, resulting in the need for technologies that allow multiple users to share the same spectrum, called Multiple Access techniques.

FDMA, TDMA and CDMA are the three major technologies available, along with variations of each.

All three technologies have one goal in common that is the most important concept to any cellular telephone systems which is “Multiple Access”, meaning that multiple, simultaneous users can be supported. In other words, a large number of users share a common pool of radio channels. The technologies differ significantly in the manner by which they accomplish this sharing.

7.2.1 Frequency Division Multiple Access

FDMA is used for standard analog cellular. Each user is assigned a discrete band of the RF spectrum.The voice signal of each user is modulated on a separate channel frequency, which is assigned 100% of the time to that user.

For example:

AMPS systems use 30 kHz "slices" of spectrum for each channel. Narrowband AMPS (NAMPS) requires only 10 kHz per channel. TACS channels are 25 kHz wide. With FDMA, only one subscriber at a time is assigned to a channel. No other conversations can access this channel until the subscriber's call is finished, or until that original call is handed off to a different channel by the system. In order to overcome this inefficiency, digital access technologies were introduced.

FDMA requires NO system timing. FDMA requires NO timing accuracy.

FDMA –based Analog system generally considered as a low capacity system.


26

Fig.21


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7.2.1.1 The Advanced Mobile Phone Service (AMPS)

AMPS was released in 1983 using the 800-MHz to 900-MHz frequency band and the 30 kHz bandwidth for each channel as a fully automated mobile telephone service. It was the first standardized cellular service in the world and is currently the most widely used standard for cellular communications. Designed for use in cities, AMPS later expanded to rural areas. It maximized the cellular concept of frequency reuse by reducing radio power output. The AMPS telephones (or handsets) have the familiar telephone-style user interface and are compatible with any AMPS base station. This makes mobility between service providers (roaming) simpler for subscribers. Limitations associated with AMPS include:

1. Low calling capacity 2. Limited spectrum

3. No room for spectrum growth 4. Poor data communications 5. Minimal privacy

6. Inadequate fraud protection

AMPS is used throughout the world and is particularly popular in the United States, South America, China, and Australia. AMPS uses frequency modulation (FM) for radio transmission. In the United States, transmissions from mobile to cell site use separate frequencies from the base station to the mobile subscriber.


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7.2.2 Time Division Multiple Access

In TDMA users are still assigned a discrete slice of RF spectrum, but multiple users now share that RF channel on a time slot basis. Each of the users alternate their use of the RF channel . Frequency Division is still used, but these carriers are now further subdivided into some number of time slots ber carrier.

A user is assigned a particular time slot in a carrier and can only send or receive information at those times. This is true wether or not the other time slots are being used. Information flow is not continuous for any user, but rather is sent and received in „bursts“ . The bursets are re-assembled at the receiving end , and appear to provide continuous sound because the process is very fast.

TDMA digital standards include North American Digital Cellular (known by its standard number IS-54), Global System for Mobile Communications (GSM), and Personal Digital Cellular (PDC).

For example, IS-54 based TDMA system, a 30 kHz channel is divided into 6 time slots each with 30 kHz band modulated signal. Although there are 6 time slots, each user needs 2 time slots, so there are a total of 3 users per 30 kHz channel. This is three times more efficient than AMPS

PDC divides 25 kHz slices of spectrum into three channels. GSM system uses both FDMA and TDMA operates with a 200 Khz bandwidth,

divided into 8 timeslots, where each user is assigned a single timeslot, thus allowing 8 users per channel frequency.

TDMA requires timing synchronization TDMA requires millisecond accuracy. GSM and TDMA are about 3 times more spectral efficient than analog.


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Fig.22


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7.2.2.1 The GSM network

The GSM technical specifications define the different entities that form the GSM network by defining their functions and interface requirements. The GSM network can be divided into four main parts: The Mobile Station (MS).

The Base Station Subsystem (BSS). The Network and Switching Subsystem (NSS).

The Operation and Support Subsystem (OSS).

• Mobile Station MS

A Mobile Station consists of two main elements: 1. The Mobile Equipment Terminal.

2. The Subscriber Identity Module (SIM). There are different types of terminals distinguished principally by their power and

application: The `fixed' terminals are the ones installed in cars. Their maximum allowed output power is 20 W.The GSM portable terminals can also be installed in vehicles. Their maximum allowed output power is 8W.

The handhels terminals have experienced the biggest success thanks to their weight and volume, which are continuously decreasing. These terminals can emit up to 2 W. The evolution of technologies allows decreasing the maximum allowed power to 0.8 W.

• The SIM (Subscriber Identity Module) The SIM is a smart card that identifies the terminal. By inserting the SIM card into

the terminal, the user can have access to all the subscribed services. Without the SIM card, the terminal is not operational. The SIM card is protected by a four-digit Personal Identification Number (PIN). In order to identify the subscriber to the system, the SIM card contains some parameters of the user such as its International Mobile Subscriber Identity (IMSI).

Another advantage of the SIM card is the mobility of the users. In fact, the only element that personalizes a terminal is the SIM card. Therefore, the user can have access to its subscribed services in any terminal using its SIM card.


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Fig.23


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• The Base Station Subsystem

The BSS connects the Mobile Station and the NSS. It is in charge of the transmission and reception. The BSS can be divided into two parts:

• The Base Transceiver Station (BTS).

• The Base Station Controller (BSC).

1. The Base Transceiver Station: The BTS corresponds to the transceivers and antennas used in each cell of the

network. A BTS is usually placed in the center of a cell. Its transmitting power defines the size of a cell. Each BTS has between one and sixteen transceivers depending on the density of users in the cell.

2. The Base Station Controller:

The BSC controls a group of BTS and manages their radio ressources. A BSC is principally in charge of handovers, frequency hopping, exchange functions and control of the radio frequency power levels of the BTSs.

Fig.24


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• The Network and Switching Subsystem Its main role is to manage the communications between the mobile users and

other users, such as mobile users, ISDN users, fixed telephony users, etc. It also includes data bases needed in order to store information about the subscribers and to manage their mobility. The different components of the NSS are described below.

1. The Mobile services Switching Center (MSC) It is the central component of the NSS. The MSC performs the switching functions

of the network. It also provides connection to other networks. 2. Home Location Register (HLR)

The HLR is considered as a very important database that stores information of the suscribers belonging to the covering area of a MSC. It also stores the current location of these subscribers and the services to which they have access. The location of the subscriber corresponds to the SS7 address of the Visitor Location Register (VLR) associated to the terminal.

3. Visitor Location Register (VLR)

The VLR contains information from a subscriber's HLR necessary in order to provide the subscribed services to visiting users. When a subscriber enters the covering area of a new MSC, the VLR associated to this MSC will request information about the new subscriber to its corresponding HLR. The VLR will then have enough information in order to assure the subscribed services without needing to ask the HLR each time a communication is established. The VLR is always implemented together with a MSC; so the area under control of the MSC is also the area under control of the VLR.

4. The Authentication Center (AuC) The AuC register is used for security purposes. It provides the parameters needed

for authentication and encryption functions. These parameters help to verify the user's identity.

5. The Equipment Identity Register (EIR) The EIR is also used for security purposes. It is a register containing information

about the mobile equipments. More particularly, it contains a list of all valid terminals. It is identified by its International Mobile Equipment Identity (IMEI). The EIR allows then to forbid calls from stolen or unauthorized terminals (e.g, a terminal which does not respect the specifications concerning the output RF power).

6. The Operation and Support Subsystem (OSS) The OSS is connected to the different components of the NSS and to the BSC, in

order to control and monitor the GSM system. It is also in charge of controlling the traffic load of the BSS. However, the increasing number of base stations, due to the development of cellular radio networks, has provoked that some of the maintenance tasks are transfered to the BTS. This transfer decreases considerably the costs of the maintenance of the system.


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Fig.25


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7.2.3 Code Division Multiple Access CDMA is a general category of digital wireless radio technologies that uses spread

spectrum techniques to modulate information across given bandwidth. IS-95 was the first application of CDMA, where information signals from all users

are simultaneously modulated across the entire channel band width (1.23 Mhz). Unique digital codes keep users separated on the 1.23 Mhz channel. All the three multiple Access technologies take advantage of the fact that radio

signals travel only a finite distance. The result is that frequencies can be reused with minimal interference after a minimum distance. The resulting assignment of frequencies is referred to “reuse pattern.”

CDMA doesn’t require frequency reuse pattern i.e. every code can be used in every sector of every cell.

In CDMA, timing is critical and aquired from the Global Positioning system”GPS” as accurate synchronization between cells is critical to CDMA operation.

CDMA also requires microsecond accuracy. The major advantage of CDMA when compared to the other technologies is its

efficient use of available spectrum, as bandwidth efficiecy directly to system capacity. The greater the efficiency, the more users can share the same spectrum, but it also can impact the amount of infrastructure equipment required to support a given number of users. This indirectly impacts the cost of operation.

In recent times, CDMA has gained widespread international acceptance by cellular radio system operators as an upgrade that will increase both their system capacity and the service quality.


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Fig.26


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8.1 Data Transmission Development

One of the problems of data transmission using GSM is posed by the current comparatively user-unfriendly usage of data services in the terminals (e.g. SMS) or the complicated connection of terminal equipment via adapter.

Terminal equipment in which different functions are integrated, as well as displays optimized for each individual data transmission form provide an answer to this.

A decisive problem is posed by the comparatively low data transmission rates of GSM Phase 1 and 2. Data transmission rates of 0.3 -9.6 kbit/s compared to 64 kbit/s using ISDN are considerably too low.

To increase the data transmission rates in the Europian system new bearer services are being developed in GSM Phase 2+, which will adapt the data transmission rates to the ISDN transmission rates in various usage areas or even, be considerably above them.

1. High Speed Circuit Switched Data HSCSD

2. General Packet Radio Service GPRS 3. Enhanced Data rates for the GSM Evolution EDGE

To increase the data transmission rates in American System after deployment of

CDMA techniques IS95B was developed, which will adapt the data transmission rates to the ISDN transmission rates in various usage.

8 Data Transmission


38

Fig.27

Fig.28


39

Chapter 2

Basic Concept of Spread Spectrum Technology


Basic Concept of Spread Spectrum Technology Contents

1

1.1 1.1.1 1.1.2 1.1.3 1.2 1.3 1.4 1.5 1.6 1.7 2

2.1 2.2 2.2.1 2.2.2 2.2.3 2.3 2.3.1 2.3.2 2.4 2.4.1 2.4.2 2.5 2.5.1 2.5.2

Advantages of CDMA Increased Capacity Lowering Eb/NO Voice Activity Detection Power Control Improved Call Quality Simplified System Planning Enhanced Privacy Improved Coverage Increased Portable Talk Time Bandwidth on Demand Spread Spectrum Technology Properties of SS signals Spread-Spectrum Multiple Access Direct Sequence Spread Spectrum Advantages of DS-SS Disadvantages of DS-SS Frequency Hopping Spread Spectrum Advantages of FH-SS Disadvantages of FH-SS Time Hopping Spread Spectrum (TH-SS) Advantages of TH-SS Disadvantages of TH-SS Hybrid Systems Advantages of H-SS Disadvantages of H-SS

2

2 2 2 2 4 4 4 4 4 4 6 8 10 10 10 10 12 12 12 14 14 14 16 16 16

1


When implemented in a cellular telephone system, CDMA technology offers many benefits to meet Mobile Radio Requirements. The following is an overview

of the advantages of CDMA.

1.1 Increased Capacity

Capacity can be increased in cellular systems in one of two ways: 1. By getting more channels per MHz of spectrum

2. By getting more channels reuse per unit of geographic area With CDMA, signals can be received in the presence of high levels of interference, All

users on a carrier share the same RF spectrum. The same CDMA RF carrier frequency is used in every cell site, and in every sector of a sector cell site.

Increasing capacity in CDMA can be done by the following techniques: -

1.1.1 Lowering Eb/No

Eb/No provides a measure of the performance of a CDMA link between the mobile and the cell. It is the ratio in dB between the energy of each information bit and the noise spectral density. The noise is a combination of background interference and the interference created by other users on the system.

CDMA describes Eb/No noise interference in terms of the Frame Erasure Rate (FER). Using an interference threshold, the CDMA system erases frames of information that contain too many errors. The FER, then, describes the number of frames that were erased due to poor quality. Therefore, as the Eb/No level increases, the FER decreases, and system voice quality is improved.

1.1.2 Voice Activity Detection

When no voice activity is detected, the vocoder will drop its encoding rate, because there is no reason to have high speed encoding of silence. The encoded rate can drop to1 kbps or less. Thus the variable rate vocoder uses up channel capacity only as needed. Since the level of "interference" created by all of the users directly determines system capacity, and voice activity detection reduces the noise level in the system, capacity can be maximized.

1.1.3 Power Control

CDMA can also increase system capacity by using POWER CONTROL, which will be discussed later.

1 Advantages of CDMA

2


Fig.1

Fig.2

3


1.2 Improved Call Quality

Cellular telephone systems using CDMA are able to provide higher quality sound and fewer dropped calls than systems based on other technologies. Advanced error detection and error correction schemes greatly increase the likelihood that frames are interpreted correctly. Sophisticated vocoders offer high speed coding and reduce background noise.

CDMA takes advantage of various types of diversity to improve speech quality.

1.3 Simplified System Planning

All users on a CDMA carrier share the same RF spectrum.

1.4 Enhanced Privacy

CDMA is an “Anti Jamming” system. In addition, since the digitized frames of information are spread across a wide slice of spectrum, it is unlikely that a casual eavesdropper will be able to listen in on a conversation.

1.5 Improved Coverage

A CDMA cell site has a greater range than a typical analog or digital cell site. Therefore fewer CDMA cell sites are required to cover the same area. Depending on system loading and interference, the reduction in cells could be as much as 50% when compared to GSM!

CDMA's greater range is due to the fact that CDMA uses a more sensitive receiver than other technologies.

1.6 Increased Portable Talk Time

Because of precise power control and other system characteristics, CDMA subscriber units normally transmit at only a fraction of the power of analog and TDMA phones. This will enable portables to have longer talk and standby time. (This direct comparison assumes, of course, similar cell sizes between the CDMA and analog or TDMA systems.)

1.7 Bandwidth on Demand

A wideband CDMA channel provides a common resource that all mobiles in a system utilize based on their own specific needs. At any given time, the portion of this "bandwidth pool" that is not used by a given mobile is available for use by any other mobile. This provides a tremendous amount of flexibility - a flexibility that can be exploited to provide powerful features, such as higher data rate services. In addition, because mobiles utilize the "bandwidth pool" independently, these features can easily coexist on the same CDMA

4


Fig.3

5


The major concern in Wireless is digital communication is efficient use of

Bandwidth and power. But there are scenarios where it is necessary to sacrifice the efficient use for design considerations. One such scenario is secure communication in hostile environment. This design objective is met using a modulation technique called as Spread Spectrum (SS).

Defining Spread Spectrum

A complete definition to Spread Spectrum is in two parts 1. Spread Spectrum is a means of transmission in which the data sequences occupy a

bandwidth in excess of the minimum bandwidth necessary to send it.

2. Spread Spectrum is accomplished before transmission through the use of a code that is independent of data sequences .The same code is used at the receiver to despread the received signal so that the original data sequence may be recovered.

In CDMA each user is assigned a unique code sequence it uses to encode its information-bearing signal. The receiver, knowing the code sequences of the user, decodes a received signal after reception and recovers the original data. This is possible since the crosscorrelations between the code of the desired user and the codes of the other users are small. Since the bandwidth of the code signal is chosen to be much larger than the bandwidth of the information-bearing signal, the encoding process enlarges (spreads) the spectrum of the signal and is therefore also known as spread-spectrum modulation. The resulting signal is also called a spread-spectrum signal, and CDMA is often denoted as spread-spectrum multiple access (SSMA) the spectral spreading of the transmitted signal gives to CDMA its multiple access capability. It is therefore important to know the techniques necessary to generate spread-spectrum signals and the properties of these signals. A spread-spectrum modulation technique must be fulfill two criteria:

The transmission bandwidth must be much larger than the information bandwidth. The resulting radio-frequency bandwidth is determined by a function other than the

information being sent (so the bandwidth is statistically independent of the information signal).

The ratio of transmitted bandwidth to information bandwidth is called the processing gain, Gp, of the spread-spectrum system; the receiver correlates the received signal with a synchronously generated replica of the spreading code to recover the original information-bearing signal. This implies that the receiver must know the code used to modulate the data.

Because of the coding and the resulting enlarged bandwidth, SS signals have a number of properties that differ from the properties of narrowband signals. The most interesting ones, from the communication systems point of view, are discussed below.

6

2 Spread Spectrum Technology


Fig.4

Fig.5

7


2.1 Properties of SS signals

• Multiple Access Capability

If multiple users transmit a spread-spectrum signal at the same time, the receiver will still be able to distinguish between the users provided each user has a unique code that has a sufficiently low cross-correlation with the other codes. Correlating the received signal with a code signal from a certain user will then only despread the signal of this user, while the other spread-spectrum signals will remain spread over a large bandwidth. Thus, within the information bandwidth the power of the desired user will be larger than the interfering power provided there are not too many interferers, and the desired signal can be extracted.

• Protection Against Multipath Interference In a radio channel there is not just one path between a transmitter and receiver. Due to reflections (and refractions) a signal will be received from a number of different

paths. The signals of the different paths are all copies of the same transmitted signal but with different amplitudes, phases, delays, and arrival angles. Adding these signals at the receiver will be constructive at some of the frequencies and destructive at others. In the time domain, this results in a dispersed signal. Spread-spectrum modulation can combat this multipath interference.

• Privacy & Interference Rejection The transmitted signal can only be despread and the data recovered if the receiver

knows the code. Cross-correlating the code signal with a narrowband signal will spread the power of the narrowband signal thereby reducing the interfering power in the information bandwidth.

• Anti-Jamming capability This is more or less the same as interference rejection except the interference is now

willfully inflicted on the system. It is this property, together with the next one, that makes spread-spectrum modulation attractive for military applications.

• Low Propability of Interception Because of its low power density, the spread-spectrum signal is difficult to detect and

intercept by a hostile listener.

8


Fig.6

Fig.7

9


2.2 Spread-Spectrum Multiple Access (SS-MA)

2.2.1 Direct Sequence Spread Spectrum (DS-SS)

In DS-CDMA the modulated information bearing signal (the data signal) is directly modulated by a digital, discrete-time, discrete-valued code signal. The data signal can be either analog or digital; in most cases it is digital.

In the case of a digital signal the data modulation is often omitted and the data signal is directly multiplied by the code signal and the resulting signal modulates the wideband carrier. It is from this direct multiplication that the direct sequence CDMA gets its name.

After transmission of the signal, the receiver uses coherent demodulation to despread the SS signal, using a locally generated code sequence. To be able to perform the dispreading operation, the receiver must not only know the code sequence used to spread the signal, but the codes of the received signal and the locally generated code must also be synchronized. This synchronization must be accomplished at the beginning of the reception and maintained until the whole signal has been received. The code synchronization/tracking block performs this operation. After despreading a data modulated signal results, and after demodulation the original data can be recovered.

2.2.2 Advantages of DS-SS:

The generation of the coded signal is easy. It can be performed by a simple multiplication.

Since only one carrier frequency has to be generated, the frequency synthesizer (carrier generator) is simple.

Coherent demodulation of the DS signal is possible.

No synchronization among the users is necessary.

2.2.3 Disdvantages of DS-SS:

It is difficult to acquire and maintain the synchronization of the locally generated code signal and the received signal. Synchronization has to be kept within a fraction of the chip time.

For correct reception the synchronization error of locally generated code sequence and the received code sequence must be very small, a fraction of the chip time.

The power received from users close to the base station is much higher than that received from users further away. Since a user continuously transmits over the whole bandwidth, a user close to the base will constantly create a lot of interference for users far from the base station, making their reception impossible. This near-far effect can be solved by applying a power control algorithm so that all users are received by the base station with the same average power. However this control proves to be quite difficult.

10


Fig.8

Fig.9

11


2.3 FREQUENCY HOPPING Spread Spectrum (FH-SS)

In frequency hopping CDMA, the carrier frequency of the modulated information signal is not constant but changes periodically. During time intervals T the carrier frequency remains the same, but after each time interval the carrier hops to another (or possibly the same) frequency. The hopping pattern is decided by the code signal.

If the hopping rate is (much) greater than the symbol rate, one speaks of a fast frequency hopping (F-FH). In this case the carrier frequency changes a number of times during the transmission of one symbol, so that one bit is transmitted in different frequencies. If the hopping rate is (much) smaller than the symbol rate, one speaks of slow frequency hopping (S-FH).

2.3.1 Advantages of FH-SS:

Synchronization is much easier with FH-CDMA than with DS-CDMA. With FH CDMA synchronization has to be within a fraction of the hop time. Since spectral spreading is not obtained by using a very high hopping frequency but by using a large hop-set, the hop time will be much longer than the chip time of a DS-CDMA system. Thus, an FH-CDMA system allows a larger synchronization error.

The different frequency bands that an FH signal can occupy do not have to be contiguous because we can make the frequency synthesizer easily skip over certain parts of the spectrum. Combined with the easier synchronization, this allows much higher spread-spectrum bandwidths.

The probability of multiple users transmitting in the same frequency band at the same time is small. A user transmitting far from the base station will be received by it even if users close to the base station are transmitting, since those users will probably be transmitting at different frequencies. Thus, the near-far performance is much better than that of DS.

Because of the larger possible bandwidth a FH system can employ, it offers a higher possible reduction of narrowband interference than a DS system.

2.3.2 Disdvantages of FH-SS:

A highly sophisticated frequency synthesizer is necessary. An abrupt change of the signal when changing frequency

12


Fig.10

13


2.4 TIME HOPPING Spread Spectrum (TH-SS)

In time hopping CDMA the data signal is transmitted in rapid bursts at time intervals determined by the code assigned to the user. The time axis is divided into frames, and each frame is divided into M time slots. During each frame the user will transmit in one of the M time slots. Which of the M time slots is transmitted depends on the code signal assigned to the user. Since a user transmits all of its data in one, instead of M time slots, the frequency it needs for its transmission has increased by a factor M.

2.4.1 Advantages of TH-SS:

Implementation is simpler than that of FH-CDMA and the near-far problem is much less of a problem since TH-CDMA is an avoidance system, so most of the time a terminal far from the base station transmits alone, and is not hindered by transmissions from stations close by.

The multiple access capability of THSS signals is acquired in the same manner as that of the FH-SS signals; namely, by making the probability of users’ transmissions in the same frequency band at the same time small. In the case of time hopping all transmissions are in the same frequency band, so the probability of more than one transmission at the same time must be small. This is again achieved by assigning different codes to different users. If multiple transmissions do occur, error-correcting codes ensure that the desired signal can still be recovered. If there is synchronization among the users, and the assigned codes are such that no more than one user transmits at a particular slot, then the THCDMA reduces to a TDMA scheme where the slot in which a user transmits is not fixed but changes from frame to frame.

2.4.2 Disdvantages of TH-SS:

In the time hopping CDMA, a signal is transmitted in reduced time. The signaling rate, therefore, increases and dispersion of the signal will now lead to overlap of adjacent bits. Therefore, no advantage is to be gained with respect to multipath interference rejection.

It takes a long time before the code is synchronized, and the time in which the receiver has to perform the synchronization is short.

If multiple transmissions occur, a large number of data bits are lost, so a good error-correcting code and data interleaving are necessary.

14


Fig.11

15


2.5 HYBRID SYSTEMS

The hybrid CDMA systems include all CDMA systems that employ a combination of two or more of the above-mentioned spread-spectrum modulation techniques or a combination of CDMA with some other multiple access technique. By combining the basic spread-spectrum modulation techniques, we have four possible hybrid systems:

DS/FH, DS/TH, FH/TH, and DS/FH/TH; and by combining CDMA with TDMA or multicarrier modulation we get two more:

CDMA/TDMA and MC-CDMA. The idea of the hybrid system is to combine the specific advantages of each of the modulation techniques.

2.5.1 Advantages of H-SS:

If we take, for example, the combined DS/FH system we have the advantage of the anti-multipath property of the DS system combined with the favorable near-far operation of the FH system.

2.5.2 Disdvantages of H-SS:

Of course, the disadvantage lies in the increased complexity of the transmitter and receiver.

Coherent demodulation is difficult because of the problems in maintaining phase relationships during hopping.

16

Fig.12

Chapter 3

CDMA codes and its usage

CDMA codes and its usage Contents

1 1.1 2 2.1 2.1.1 2.1.2 2.2 2.2.1 2.2.2 2.2.3 2.3 2.4 2.5 2.5.1 2.5.2

Iterium Standard-95 System IS – 95 Pseduo Random Noise Sequence PN Sequence PN Sequence generation PN Generator Example Types of PN Sequences in CDMA Short Code Long Code Walsh Code Correlation Between PN Sequences Process Gain and Its Benefits Spreading Code Acquisition and Tracking Initial Code Acquisition Code Tracking

2 2 4 4 6 8 9 9 9 11 12 14 16 18 20


1

1.1 IS-95 Interim Standard 95 (IS-95) is a U.S. digital cellular system based on CDMA that

allows each user within a cell and in adjacent cells to use the same radio channel. Each IS-95 channel occupies 1.23MHz of spectrum in each one-way link; the user

data is spread to a channel chip rate of 1.2288MHz. IS-95 uses a different modulation and spreading technique for the forward and reverse links. On the forward link, the base station simultaneously transmits the user data for all mobiles in the cell by using different spreading sequence for each mobile. The user data is encoded, interleaved, and spread by one of sixty-four orthogonal spreading sequences (Walsh functions).

To avoid interference, all signals in a particular cell are scrambled using a pseudorandom sequence of length 215-1 chips.

CDMA base stations transmit information in four logical channel formats:

Pilot channels, sync channels, paging channels, and traffic channels.

On the reverse link, all mobiles respond in an asynchronous fashion. The user data is encoded, interleaved, and then blocks of 6 bits are mapped to one of the 64 orthogonal Walsh functions. Finally, the data is spread by a user specific code of 42 bits (channel identifier) and the base station pseudorandom sequence of length 215 chips. The reverse channel is organized in:

Access channels and traffic channels. At both the base station and the terminal, Rake receivers are used to resolve and

combine multipath components, in order to improve the link quality. In IS-95, a three-finger Rake receiver is used at the base station.


1 Iterium Standard-95 System

2

Fig.1


3

2.1 PN Sequences • What are PN sequences?

A Pseudo-random Noise (PN) sequence is a sequence of binary numbers, e.g. ±1, which appears to be random; but is in fact perfectly deterministic. The sequence appears to be random in the sense that the binary values and groups or runs of the same binary value occur in the sequence in the same proportion they would if the sequence were being generated based on a fair "coin tossing" experiment. In the experiment, each head could result in one binary value and a tail the other value. The PN sequence appears to have been generated from such an experiment. A software or hardware device designed to produce a PN sequence is called a PN generator.

Pseudo-random noise sequences or PN sequences are known sequences that exhibit the properties or characteristics of random sequences. They can be used to logically isolate users on the same frequency channel. They can also be used to perform scrambling as well as spreading and despreading functions. The reason we need to use PN sequences is that if the code sequences were deterministic, then everybody could access the channel. If the code sequences were truly random on the other hand, then nobody, including the intended receiver, would be able to access the channel. Thus, using a pseudo-random sequence makes the signal look like random noise to everybody except to the transmitter and the intended receiver.

• Why PN sequence is chosen as a noise like waveform? To know that we have to understand what is called “white Noise”. The adjective “white” is used in the sense that white light contains equal amounts of all

frequencies within the visible band of electromagnetic radiation. It has power spectral density independent of the operating frequency. We express the

power spectral density of white noise by Sw (f) = No/2 ... No = KT0 watts /Hz. where K is Boltzman constant & T0 is the equivalent noise temperature.

• Equivalent noise temperature of a system “T0”: - It is the temperature at which a noisy resistor has to be maintained such that, by

connecting the resistor to the input of a noiseless version of the system, it produces the same available noise in the actual system it depends only on the parameters of the system

Since the auto correlation function is the inverse Fourier of the power spectral density it follows that for white noise, the auto correlation function of white noise consists of a delta function weighted by the factor No/2 and occurring at τ = 0.

Accordingly, any two different samples of white noise, no matter how closely together in time, they are taken, are uncorrelated. So we have to search for a code sequence has a noise like wave or almost has autocorrelation function near that of white noise.


2 Pseduo Random Noise Sequence

4

Fig.2


5

2.1.1 PN Sequence Generation

These sequences are easily generated by using an M-bit linear feedback shift register with the appropriate feedback taps, e.g. as shown in Fig. For M = 5. With the appropriate taps, the length (N) of the serial bit stream at the output will be a maximum (Lmax): N = Lmax = 2M - 1

The meaning of bit-stream length in this context is the maximum length of the bit sequence before it starts repeating itself. PN sequences of maximum length are called maximal linear code sequences, but because non-maximal PN sequences are rarely used in SS systems, “PN sequences” will be used to denote maximal linear code sequences for this document. Also “PN codes” or “PN code sequences” will be used synonymously with “PN sequences”. The feedback taps are added modulo-2 (exclusive OR’ed) and fed to the input of the initial shift register. Only particular tap connections will yield a maximum length for a given shift register length. These maximal length PN codes have the following properties:

1. Code balance: The number of ones and the number of zeros differ by only 1, i.e., there is 1 more one

than the number of zeros. This particularly useful when the channel is AC coupled (no DC transmission).

2. Autocorrelation: Using signaling values of ±1, the autocorrelation of a PN sequence has a value of –1 or

all phase shifts of more than one bit time. For no has shift (perfect alignment with itself), the autocorrelation has a value of N, the sequence length.

3. Modulo-2 addition: Modulo-2 addition of a PN sequence with a shifted version of itself results in a differently

shifted version of itself. 4. Shift Register States:

The binary number represented by the M bits in the shift register randomly cycle through all 2M values, except for 0, in successive 2M-1 clocks.

If the value of 0 (all shift register bits are 0) is ever present in the shift register, it will stay in that state until reloaded with a nonzero value.


6

Fig.3

Fig.4


7

2.1.2 A PN Generator Example

A PN generator is typically made of N cascaded flip-flop circuits and a specially selected feedback arrangement. The flip-flop circuits when used in this way are called a shift register since each clock pulse applied to the flip-flops causes the contents of each flip-flop to be shifted to the right. The feedback connections provide the input to the left-most flip-flop. With N binary stages, the largest number of different patterns the shift register can have is 2N. The all-binary-zero state, however, is not allowed because it would cause all remaining states of the shift register and its outputs to be binary zero. The all-binary-ones state does not cause a similar problem of repeated binary ones provided the number of flip-flops input to the modulo-2 adder is even. The period of the PN sequence is therefore 2N -1. For example, starting with the register in state 001, the next 7 states are 100, 010,101, 110, 111, 011, and then 001 again and the states continue to repeat. The output taken from the right-most flip-flop is 1001011 and then repeats. With the three-stage shift register, the period is 23-1 or 7.


Fig.5

8

2.2 Types of PN Sequences in CDMA There are two different types of PN codes and one output of Hadamard Matrix

used in IS-95 CDMA Technology:

1. Short PN code 2. Long PN code 3. Walsh codes

IS-95 uses the two types of maximum-length PN generators to spread the signal power uniformly over the physical bandwidth of about 1.25 MHz. The PN spreading on the reverse link also provides near orthogonality of and hence, minimal interference between signals from each mobile. This allows reuse of the band of frequencies available, which is a major advantage of CDMA.

2.2.1 Short Code: A 15-stage linear shift register generates the short PN code. Therefore, the maximum

length of the Short PN Code is L = 2N-1 = 215-1 = 32,768-1 chips.

By implementation, an extra chip is inserted at the end of the sequence, yielding a sequence of length L=32,768 chips. The short PN code runs at a speed of 1,228,800 chips per second. This yields a repetition cycle of 32,768/1,228,800=26.67 ms.

The short PN code consist of two PN Sequences I and Q each 32,768 chips long generated in similar but differently tapped 15 bit shift register, the two sequences scramble the information on the I and Q phase channels. § These codes are used for cell identification in a reused cell. § The chip rate of the short PN code is 1.2288 Mcps.

2.2.2 Long Code: The PN chips from the long code are used to provide several randomizing functions in

the IS-95 system. These include providing chips for message-scrambling on the forward and reverse links, for identifying individual mobiles and access channels on the reverse links by using unique offsets for each entity and for randomizing the location of the power control bits on the forward traffic channels. A 42-stage linear shift register generates the long PN code. Therefore, the maximum length of the long PN code is

L = 2N-1 = 242-1 = 4.4 x 1012 = 4.4 trillion chips. The Long PN Code also runs at a speed of 1,228,800 chips per second. This yields a

repetition cycle of 4.4 x 1012/1,228,800 = 41-42 days. The long PN code is generated in a 42-stage linear shift register generator with the

output of the 42nd stage input into the first stage and modulo-2 added with the outputs of stages 1, 2, 3, 5, 6, 7, 10, 16, 17, 18, 19, 21, 22, 25, 26, 27, 31, 33, and 35. The output of the long code generator is taken after the output of each flip-flop in the generator has been added with a corresponding bit in a 42-bit mask, which is unique to each user, access, and paging channel. § Base band data scrambling in the forward link § Base band data spreading in the reverse link


9

Fig.6

Fig.7


10

2.2.3 Walsh code: In 1923, J.L. Walsh introduced a complete set of orthogonal codes, based on rearranging the Rademacher code. These codes are also binary valued codes. The Walsh code, also known as the Hadamard code, is a set of 64 orthogonal codes, there purpose is to provide:

1. Forward channel spreading over the 1.2288MHz band; 2. Unique identification to a mobile.

The chip rate (code rate) of a Walsh code is 1.2288 Mchips per second (Mcps). The four different types of forward channels are designated as follows:

1. Pilot channel: W0 (Walsh code 0); 2. Paging channel: W1 to W7 (unused paging codes can be used for traffic); 3. Sync channel: W32; 4. Traffic channel: W8 to W31 and W33 to W63.


Fig.8

11

2.3 Correlation between PN sequences The correlation of two random variables x(t) and y(t), is a time-shift comparison which

expresses the degree of similarity or the degree of likeness between the two variables. The Auto-Correlation function R, provides the degree of similarity between a random variable x(t) and a time-shifted version of x(t).

Likewise, the cross-correlation function provides the degree of similarity, or the degree of likeness between a random variable x(t) and time-shifted version of another random variable y(t). To get the average value of the auto-correlation or cross-correlation, a normalization by the sequence length L is required. Consider Ci(t) and the time-shifted version of itself, say Ci(t-1)

Ci(t) = 1 0 0 1 1 1 0 Ci(t-1) = 0 0 1 1 1 0 1

When corresponding bits from the two sequences have the same parity (or match each other), we call the match an agreement "A". Likewise, when corresponding bits from the two sequences do not have the same Parity (do not match each other), we call the mismatch a disagreement "D" .By counting all the agreements and all the disagreements over the full length L of the sequence, a measure of correlation can be estimated as:

Correlation = Total number of "A" - Total number of "D" Now, consider the reference PN code C i(t) and its time-shifted versions as shown. Now let us compute the correlation of C i(t) and Ci(t-t), for all suitable values of t (here

from 0 to 7). In general, it can be shown that the full-length auto-correlation function (R) of PN codes

or PN sequences is characterized by a large positive number equal to the length of the PN sequence (R=2n-1) when time shift=0, and -1 for all time-shifts equal or greater than the duration of one chip. So when normalized by the length, the auto-correlation function is equal to 1 at time-shift zero and is very small (-1/L) for all values of time shifts equal or greater than one chip.

In summary, the auto-correlation function of PN codes is a two-value function. Its maximum value occurs when the time-shift parameter is zero. For all other values equal to or greater than one chip, the correlation function is -1.

• Orthogonality of PN sequences Consider the reference PN Code Cj(t) and the time-shifted versions of another code Ci(t)

as shown. Let us compute the cross-correlation of Cj(t) and Ci(t-t) for all suitable values of t (0 to 7).

Two PN sequences Ci(t) and Cj(t) are said to be orthogonal if and only if their respective normalized correlation function is equal to 1 at a time-shift of zero and their cross correlation function is equal to zero for all time-shift values. As shown above, averaged over the code length, the cross-correlation function of PN sequences is not zero. As a result, PN sequences are not perfectly orthogonal.


12

Fig.9

Fig.10


13

2.4 Process Gain and its Benefits The primary benefit of processing gain is its contribution towards jamming resistance to

the DSSS signal. The PN code spreads the transmitted signal in bandwidth and it makes it less susceptible to narrowband interference within the spread BW. The receiver of a DSSS system can be viewed as unspreading the intended signal and at the same time spreading the interfering waveform. This operation is best illustrated on Figure, which, depicts the power spectral density (psd) functions of the signals at the receiver input, the despread signal, the band pass filter power transfer function, and the band pass filter output. The figure graphically describes the effect of the processing gain on a jammer. The jammer is narrow, and has a highly peaked psd, while the psd of the DSSS is wide and low. The despreading operation spreads the jammer power psd and lowers its peak, and the BPF output shows the effect on the signal to jammer ratio.

If for example, BPSK modulation is used and an Eb/No of lets say 14dB is required to achieve a certain BER performance, when this waveform is spread with a processing gain of 10dB then the receiver can still achieve its required performance with the signal having a 4dB power advantage over the interference. This is derived from the 14dB required minus the 10dB of PG.

The higher the processing gain of the DS-SS waveform the more the resistance to interference of the DSSS signal. If a code with a length of 16 bits is to be used then the processing gain is equivalent to 10 Log[16] dB or 12.04dB.


14

We can define GP as:

Where SNRo and SNRi are the output and input SNR of the correlator, respectively. Where BWD and BWSS are the bandwidth of the data before and after SS modulation. Fig.11


15

2.5 Spreading Code Acquisition and Tracking No matter which form of spread spectrum technique we employ, we need to have the

timing information of the transmitted signal in order to despread the received signal and demodulate the despread signal. For a DS-SS system, we see that if we are off even by a single chip duration, we will be unable to despread the received spread spectrum signal, since the spread sequence is designed to have a small out-of-phase autocorrelation magnitude. Therefore, the process of acquiring the timing information of the transmitted spread spectrum signal is essential to the implementation of any form of spread spectrum technique. Usually the problem of timing acquisition is solved via a two-step approach:

• Initial code acquisition (coarse acquisition or coarse synchronization), which synchronizes the transmitter and receiver.

• Code tracking, which performs and maintains fine synchronization between the transmitter and receiver.

Given the initial acquisition, code tracking is a relatively easy task and is usually accomplished by a delay lock loop (DLL). The tracking loop keeps on operating during the whole communication period. If the channel changes abruptly, the delay lock loop will lose track of the correct timing and initial acquisition will be reperformed. Sometimes, we perform initial code acquisition periodically no matter whether the tracking loop loses track or not.

Compared to code tracking, initial code acquisition in a spread spectrum system is usually very difficult. First, the timing uncertainty, which is basically determined by the transmission time of the transmitter and the propagation delay, can be much longer than a chip duration. As initial acquisition is usually achieved by a search through all possible phases (delays) of the sequence, a larger timing uncertainty means a larger search area. Beside timing uncertainty, we may also encounter frequency uncertainty that is due to Doppler shift and mismatch between the transmitter and receiver oscillators. Thus this necessitates a two-dimensional search in time and frequency. Moreover, in many cases, initial code acquisition must be accomplished in low signal-to-noise-ratio environments and in the presence of jammers. The possibility of channel fading and the existence of multiple access interference in CDMA environments can make initial acquisition even harder to accomplish.

The problem of achieving synchronization in various fading channels and CDMA environments is difficult and is currently under active investigation. In many practical systems, side information such as the time of the day and an additional control channel, is needed to help achieve synchronization.


16

Fig.12


17

2.5.1 Initial Code Acquisition

As mentioned before, the objective of initial code acquisition is to achieve a coarse synchronization between the receiver and the transmitted signal. In a DS-SS system, this is the same as matching the phase of the reference-spreading signal in the despreader to the spreading sequence in the received signal. We are going to introduce several acquisition techniques, which perform the phase matching just described.

• Acquisition strategies

Serial search

The first acquisition strategy we consider is serial search. In this method, the acquisition circuit attempts to cycle through and test all possible phases one by one (serially) as shown in Figure.

The circuit complexity for serial search is low. However, penalty time associated with a miss is large.

Therefore we need to select a larger integration (dwell) time to reduce the miss probability. This, together with the serial searching nature, gives a large overall acquisition time (i.e., slow acquisition).


Fig.13

18

Parallel search

Unlike serial search, we test all the possible phases simultaneously in the parallel search strategy as shown in figure. Obviously, the circuit complexity of the parallel search is high. The overall acquisition time is much smaller than that of the serial search.


Fig.14

19

CDMA Air Interface Overview

2.5.2 Code Tracking

The purpose of code tracking is to perform and maintain fine synchronization. A code-tracking loop starts its operation only after initial acquisition has been achieved. Hence, we can assume that we are off by small amounts in both frequency and code phase. A common fine synchronization strategy is to design a code tracking circuitry, which can track the code phase in the presence of a small frequency error. After the correct code phase is acquired by the code tracking circuitry, a standard phase lock

Loop (PLL) can be employed to track the carrier frequency and phase. In this section, we give a brief introduction to a common technique for code tracking, namely, the early-late gate delay-lock loop (DLL).

Fig.15

20

Chapter 4




Contents

1

1.1 1.2 1.2.1 1.2.2 1.2.3 1.2.4 1.2.5 1.3 1.3.1 1.3.1 1.3.2 1.3.2 1.4

CDMA Air Links and Channels CDMA Air Links Forward Link Channels Pilot Channel Sync Channel Paging Channel Rate Set 1Traffic Channel Rate Set 2 Traffic Channel Reverse Link Channels Access Channel Access Channel (Cont.) Traffic Channel Traffic Channel (Cont.) How calls from a BTS are encoded and transmitted to a cellphone

2 2 4 4 6 7 9 11 12 12 14 15 16 17

1


1.1 CDMA Air- Links The IS-95 CDMA system is unique in that its forward and reverse links have different link

structure. This is necessary to accommodate the requirements of a land-mobile communication system. The forward link consists of four types of logical channels: pilot, sync, paging, and traffic channels. There is one pilot channel, one sync channel, up to seven paging channels, and several traffic channels. Each of these forward-link channels is first spread orthogonally by its Walsh function, and then a quadrature pair of short PN sequences spreads it.

All channels are added together to form the composite SS signal to be transmitted on the forward link.

The reverse link consists of two types of logical channels: access and traffic channels. Each of these reverse-link channels is spread orthogonally by a unique long PN sequence; hence, each channel is identified using the distinct long PN code. The reason that a pilot channel is not used on the reverse link is that it is impractical for each mobile to broadcast its own pilot sequence.

Forward Link

We defined the structure of a Hadamard matrix and described how Walsh codes are generated using such a matrix. The IS-95 CDMA system uses a 64 by 64 Hadamard matrix to generate 64 Walsh functions that are orthogonal to each other, and each of the logic channels on the forward link is identified by its assigned Walsh function.

Reverse Link The reverse link supports two types of logical channels: Access channels and Traffic

channels.

Because of the noncoherent nature of the reverse link, Walsh functions are not used for channelization. Instead, Long PN sequences are used to distinguish the users from one another.

1 CDMA Air- Links and Channels

2


Fig.1

Fig.2

3


1.2 Forward Link Channels

1.2.1 Pilot Channel The pilot channel is is used by the base station to provide a reference for all mobile

stations. It provides a phase reference for coherent demodulation at the mobile receiver to enable coherent detection. It is assigned the Walsh code W0.

The pilot signal level for all base stations is kept about 4 to 6 dB higher than the traffic channel with a constant signal power. The pilot is used for comparisons of signal strength between different base stations to decide when to perform handoff. The pilot signals from all base stations use the same PN sequences, but each base station is identified by a unique time offset. These offsets are in increments of 64 chips to provide 512 unique offsets.

Each terminal segregates the set of PN Offset values (and implicitly the set of base stations) in a system into four categories:

• The active list contains base stations currently used for traffic channel transmissions. In a soft handoff condition, there is more than one base station in this list.

• The candidate list consists of base stations classified by the terminal, on the basis of measured signal quality, as available for traffic channel transmissions.

• The neighbor list is a set of nearby base stations that could soon be available for handoff.

• The remaining list contains the base stations that are not in any of the other categories.

4


Fig.3

5


1.2.2 Sync Channel

Unlike the pilot channel, the sync channel carries baseband information. The information is contained in the sync channel message that notifies the mobile of important information about system synchronization and parameters.

The baseband information is error protected and interleaved, it is then spread by Walsh function 32 and further spread by the PN sequence that is identified with the serving sector. The baseband information is at a rate of 1.2 Kbps.

The Sync Channel is used with the pilot channel to acquire initial time synchronization. The Sync channel message parameters are:

• System Identification (SID)

• Network Identification (NID)

• Pilot short PN sequence offset index

• Long-code state

• System time

• Offset of local time

• Daylight saving time indicator

• Paging Channel data rate (4.8 or 9.6kbps).

Fig.4

6


1.2.3 Paging Channel

Similar to the sync channel, the paging channel also carries baseband information. But unlike the sync channel, the paging channel transmits at higher rates; it can transmit

at either 4.8 or 9.6 Kbps. As shown in Figure, the baseband information is first error protected, and then if the data rate is at 4.8 Kbps, the bits are repeated once. Otherwise, they are not repeated. Following interleaving, the data is first scrambled by a decimated long PN sequence, then it is spread by a specific Walsh function assigned to that paging channel and further spread by the short PN sequence assigned to the serving sector. Also note from Figure that the long PN code undergoes a decimation ratio of 64:1 (i.e., from 1.2288 Mcps to 19.2 Ksps). The long-code generator itself is masked with a mask specific to each unique paging channel number (i.e., 1 through 7). Therefore, the longcode mask used for paging channel 1 (spread by Walsh function 1) is different from that used for paging channel 3 (spread by Walsh function 3).

Some of the messagescarried by the paging channel include:

• System Parameter message: such as base station identifier, the number of paging channels, and the page channel number.

• Access Parameters message: parameters required by the mobile to transmit on an access channel.

• Neighbor List Message: information about neighbor base station parameters, such as the PN Offset.

• CDMA Channel List message: provides a list of CDMA carriers. • Page message: provides a page to the mobile station. • Channel Assignment message: to inform the mobile station to tune to a new

frequency. • Data Burst message: data message sent by the base station to the mobile. • Authentication Challenge: allows the base station to validate the mobile identity.

7


Fig.5

8


1.2.4 Rate Set1 Traffic Channel

The forward traffic channel is used to transmit user data and voice; signaling messages are also sent over the traffic channel.

For Rate Set 1, the vocoder is capable of varying its output data rate in response to speech activities. Four different data rates are supported: 9.6, 4.8, 2.4, and 1.2 Kbps. For example, during quiet periods of speech, the vocoder may elect to code the speech at the lowest rate of 1.2 Kbps.

The baseband data from the vocoder is convolutionally encoded for error protection. For Rate Set 1, a rate 1/2 convolutional encoder is used. The encoding effectively doubles the data rate. After convolutional encoding, the data undergoes symbol repetition, which repeats the symbols when lower rate data are produced by the vocoder. The following is the repetition scheme:

• When the data rate is 9.6 Kbps, the code symbol rate (at the output of the convolutional encoder) is 19.2 Ksps. In this case, no repetition is performed.

• When the data rate is 4.8 Kbps, the code symbol rate is 9.6 Ksps; each symbol is repeated once, yielding a final modulation symbol rate of 19.2 Ksps.

• When the data rate is 2.4 Kbps, the code symbol rate is 4.8 Ksps; each symbol is repeated three times, yielding a final modulation symbol rate of 19.2 Ksps.

• When the data rate is 1.2 Kbps, the code symbol rate is 2.4 Ksps; each symbol is repeated seven times, yielding a final modulation symbol rate of 19.2 Ksps.

The reason for repeating symbols is to reduce overall interference power at a given time when lower rate data are transmitted.

In a real CDMA system, when the vocoder is transmitting at 4.8 Kbps, the energy per symbol transmitted is one-half that of 9.6 Kbps. When the vocoder is transmitting at 2.4 Kbps, the energy per symbol transmitted is oneforth that of 9.6 Kbps, and when the vocoder is transmitting at 1.2 Kbps, the energy per symbol transmitted is one-eighth that of 9.6 Kbps.

After symbol repetition, the data is interleaved to combat fading (see Figure), and then the interleaved data is scrambled by a decimated long PN sequence. A long PN code generator generates the long PN sequence. The generator outputs a long PN sequence at 1.2288 Mcps. Because the data rate at the interleaver output is 19.2 Ksps, the PN sequence is decimated by a ratio of 64:1 to also achieve a rate of 19.2 Kcps; the decimated long PN sequence at 19.2 Kcps is then multiplied with the 19.2-Ksps data stream. Note that the long-code generator produces the long PN sequence using a mask that is specific to the mobile.

9


Fig.6

10


1.2.5 Rate Set 2 Traffic Channel

The forward traffic channel structure is similar for Rate Set 2. The Rate Set 2 vocoder codes speech at higher rates, and it delivers a better voice quality than that of Rate Set 1. The Rate Set 2 vocoder supports four variable rates: 14.4, 7.2, 3.6, and 1.8 Kbps.

Note that in order to maintain the output of the block interleaver at 19.2 Ksps, the

rate of the convolutional encoder is increased to R = 3/4.

Fig.7

11


1.3 Reverse Link channels The reverse link supports two types of logical channels: Access channels and Traffic

channels.

Because of the noncoherent nature of the reverse link, Walsh functions are not used for channelization. Instead, Long PN sequences are used to distinguish the users from one another.

1.3.1 Access Channel

The mobile communicates with the base station when it doesn’t have a traffic channel assigned using the access channel. The mobile uses this channel to make call originations and respond to pages and orders. The baseband data rate of the access channel is fixed at 4.8 Kbps.

The baseband information is first error protected by an R = 1/3 convolutional encoder. The lower encoding rate makes error protection more robust on the reverse link, which is often the weaker of the two links. The symbol repetition function repeats the symbol once, yielding a code symbol rate of 28.8 Ksps. The data is then interleaved to combat fading. Following interleaving, the data is coded by a 64-ary orthogonal modulator.

The set of 64 Walsh functions is used, but here the Walsh functions are used to modulate, or represent, groups of six symbols. The reason for orthogonal modulation of the symbols is again due to the noncoherent nature of reverse link. When a user’s transmission is not coherent, the receiver (at the base station) still has to detect each symbol correctly. Making a decision of whether or not a symbol is +1 or -1 may be difficult during one symbol period.

However, if a group of six symbols is represented by a unique Walsh function, then the base station can easily detect six symbols at a time by deciding which Walsh function is sent during that period. The receiver can easily decide which Walsh function is sent by correlating the received sequence with the set of 64 known Walsh functions. Note that on the forward link, Walsh functions are used to distinguish among the different channels. On the reverse link, Walsh functions are used to distinguish among the different symbols (or among groups of six symbols). The orthogonally modulated data at 4.8 Ksps (modulation symbols) or at 307.2 Ksps (code symbols) are then spread by the long PN sequence. The long PN sequence is running at 1.2288 Mcps, and the bandwidth of the data after spreading is 1.2288 Mcps. Remember that the long PN sequence is used to distinguish the access channel from all other channels that occupy the reverse link. The data is further scrambled in the I and the Q paths by the short PN sequences (also running at 1.2288 Mcps) defined in the IS-95 standard.

12


Fig.8

13


1.3.1 Access Channel (Cont.) Is used by a terminal without a call in progress to send messages to the base station for

three principal purposes: to originate a call, to respond to a paging message, and to register its location. Each base station operates with up to 32 access channels. The messages carried by the access channel include:

• Registration Message: sends to the base station information necessary to page the mobile, such as: location, status, and identification.

• Order message: to transmit information such as base station challenge, mobile station acknowledgement, local control response, and mobile station reject.

• Data Burst message: user-generated data message sent by the mobile station to the base station.

• Origination message: allows the mobile station to place a call’ sending dialed digits. • Page Response message: used to respond to a page. • Authentication Challenge Response message: contains necessary information to

validate the mobile station’s identity.

Fig.9

14


1.3.2 Traffic Channel

The reverse traffic channel is used to transmit user data and voice; signaling messages are also sent over the traffic channel. The structure of the reverse traffic channel is similar to that of the access channel. The major difference is that the reverse traffic channel contains a data burst randomizer.

The orthogonally modulated data is fed into the data burst randomizer. The function of the data burst randomizer is to take advantage of the voice activity factor on the reverse link. Recall that the forward link uses a different scheme to take advantage of the voice activity factor, when the vocoder is operating at a lower rate, the forward link transmits the repeated symbols at a reduced energy per symbol and thereby reduces the forward-link power during any given period.

The approach taken to reduce reverse-link power during quieter periods of speech is to pseudorandomly mask out redundant symbols produced by symbol repetition.

This is accomplished by the data burst randomizer. The data burst randomizer generates a masking pattern of 0s and 1s that randomly masks out redundant data. The masking pattern is partially determined by the vocoder rate. If the vocoder is operating at 9.6 Kbps, then no data is masked. If the vocoder is operating at 1.2 Kbps, then the symbols are repeated seven times, and the data burst randomizer masks out, on average, seven out of eight groups of symbols.

Fig.10

Fig.10

15


1.3.2 Traffic Channel (Cont.)

This channel can multiplex primary (voice) and secondary (data) or signaling traffic. Some of the typical messages that the reverse traffic channel carries are:

• Order messages: include base station challenge, parameter update confirmation, mobile station acknowledgement, service option request and response, release, connect, DTMF tone, etc.

• Authentication Challenge Response message: information to validate the mobile station.

• Data Burst message: a user-generated data message sent by the mobile to the base station.

• Pilot Strength Measurement message: information about the strength of other pilot signals that are not associated with the serving base station.

• Power Measurement Report message: sends FER statistics to the base station. • Handoff Completion message: is the mobile response to a Handoff Direction

message. • Parameter Response message: is the mobile response to the base station to a

Retrieve Parameters message.

Fig.11

16


1.4 How calls from a base station are encoded and transmitted to a cellphone

At the base station, each voice conversation is converted into digital code and compressed with a vocoder. The vocoder output is doubled by a convolutional encoder that adds redundancy for error checking. Each bit from the encoder is replicated 64 times and exclusive OR'd with a Walsh code that is used to identify that call from the rest. The output of the Walsh code is exclusive OR'd with the next string of bits (PN sequence) from a pseudo-random number generator, which is used to identify all the calls in a particular cell's sector. At this point, there is 128 times as many bits as there were from the vocoder's output. All the calls are combined and modulated onto a carrier frequency in the 800 MHz range.

At the receiving side, the received signals are quantized (turned into bits) and run through the Walsh code and PN sequence correlation receiver to recover the transmitted bits of the original signal. When 20ms of voice data is received, a Viterbi decoder corrects the errors using the convolutional code, and that all goes to the vocoder that turns the bits back into waveforms (sound).

17

1.4 How calls from a base station are encoded and transmitted to a cellphone


Fig.12

18

Chapter 5

CDMA System Aspects

CDMA System Aspects

CDMA System Aspects Contents

1 Power Control in CDMA 2

1.1 1.1.1 1.1.2 1.2 1.2.1 1.2.2 1.2.3 2 2.1 3 3.1 3.2 3.2.1 3.3 44

Introduction Effect of No Power Control The NEAR – FAR Problem Classification of Power Control Techniques According to update strategies According to direction of transmission According to techniques Rake Receiver Rake Receiver Theory and Structure Handoff Versus Handover Handoff Versus Handover Soft Handover The Importance Of Soft Handoff Softer Handover Multiuser Detection

2 2 2 4 4 6 8 9 9 11 11 11 11 12 14

1

CDMA System Aspects

1.1 Introduction

Power control is one of the most important system requirement, and it is analyzed for cellular networks based on FDMA and TDMA, and for DS-CDMA cellular networks, In most modern systems, both base stations and mobiles have the capability of real-time (dynamic) adjustment of their transmit powers.

1.1.1 Effect of NO Power Control:

In case of no power control, if a mobile station signal is received at the base station with a too low level of received power [MS is far from the cell site, or in an unusual high attenuation channel], High level of interference is experienced by this mobile and its performance (BER) will be degraded.

On the other hand, if the received power level is too high, the performance of this mobile is acceptable, but increases interference to all other mobile stations that are using the same channel.

Fast power control greatly optimizes the system capacity,but since many subscribers transmit in the same frequency band and the same frequency can be used in each cell (re-use = 1), each user can cause interference for the others.

The power control is used to solve the called “NEAR-FAR” problem.

1.1.2 The (NEAR – FAR) Problem

In ideal cases, the power received at the BTS is identical for all UE served by the BTS (assuming the transfer rates are identical). This ideal situation also represents the maximum capacity of the cell.

Genuine fast power control is necessary because of the mobility of the UE. This mobility causes rapid variation in the attenuation of the power of the UE. Let us consider the shown example:

If the mobiles are permitted to transmit the same power from two different distances, the ratio of the received signals at the base station will be not equal. Therefore, the objective of the mobile power control is to produce a nominal received power from all mobiles in a given cell or a sector. Because of that, well-defined power control is essential for proper functioning of the DS-CDMA system. In the absence of power control the capacity of the DS-CDMA mobile system is very low, even lower than that of mobile systems based on FDMA. One of the reasons for the use of power control both in FDMA/TDMA and in DS-CDMA networks is to prolong battery life by using a minimum of transmitter power to achieve the required transmission quality. According to the above-mentioned facts, for proper operation of a modern high-capacity cellular radio system, power control is an essential feature.

1 Power Control in CDMA

2

CDMA System Aspects

Fig.2

Fig.1

3

CDMA System Aspects

1.2 Classification of Power Control Techniques According to what is measured to determine power control command, power

control techniques can be classified into: 1. Strength-based. 2. SIR-based.

3. BER-based. 1. Strength-based.

The strength of a signal arriving at the base station from a mobile is measured to determine whether it is higher or lower than the desired strength and then it is adjusted so it is considered the easiest method.

2. SIR-based. The measured quantity is the Signal to Interference Ratio where interference consists of

channel noise and multi-user interference. SIR-based power control reflects better system performance such as QoS and capacity. A serious problem associated with SIR-based power control is the potential to get positive feedback to endanger the stability of the system.

3. BER-based.

Bit Error Rate is defined as an average number of erroneous bits compared to the original sequence of bits. If the signal and interference powers are constant, the BER will be a function of the SIR, and in this case the QoS is equivalent. However, in reality the SIR is time-variant and thus the average SIR will not correspond to the average BER. In this case the BER is a better quality measure.

1.2.1 According to update strategies, power control

algorithms can be classified as follows: 1. Fixed step size algorithm 2. Adaptive step size to the channel variation 1. Fixed step size algorithm

Power control command in fixed step size algorithms is a simple 1-bit command. It has been shown that the inverse algorithm is superior to the fixed step size algorithm. However, the fixed step size algorithm is easier to implement because the inverse algorithm needs additional bandwidth on the return channel to carry the power control step size instead of the1-bit control command as in fixed step size algorithm. A compromise would be to use an adaptive delta-modulation algorithm.

2. Adaptive step size to the channel variation

A specific example of the adaptive step size approach is the inverse update algorithm, which increases or decreases the mobile users' transmit power by the actual difference between the received signal power and the desired received signal power.

4

CDMA System Aspects

Fig.3

5

CDMA System Aspects

1.2.2 According to direction of transmission , power control can be classified into:

1. Forward link (from mobiles to base stations). 2. Reverse link (from base stations to mobiles). 1. Forward link power control:

Forward link (base station to mobile) power control is a one step process .The base station controls its transmitting power so that a given mobile receives extra power to overcome fading, interference, BER, etc. In this mechanism, the cell site reduces its transmitting power while the mobile computes the frame error rate (FER). Once the mobile detects 1% FER, it sends a request to stop the power reduction.

2. Reverse Link Power Control Power control for the reverse link is a combined technique consisting of closed-loop and

open-loop power controls. Also, it is a fixed step size algorithm and strength-based distributed algorithm. The goal of open-loop power control is the estimation of a path loss and a loss due to shadowing between the base and the mobile station. According to this process, the mobiles transmit the initial power control signal.

However, multipath fading in a reverse and a forward DS-CDMA link is an independent process since the frequency separation of these links is 45MHz and it greatly exceeds the coherent bandwidth of the channel. Thus, closed-loop power control is used. Every cell site demodulator measures the received signal-to-noise ratio (SNR) from each mobile station. The measured SNR is compared to the desired SNR for that mobile station and a power adjustment command is sent to the mobile station. This power adjustment command is combined with the mobile station open-loop estimate to obtain the final value of the mobile station transmit power. The base station measures the signal quality (BER) and based on that determines the desired SNR for specific mobile station. In previously described power control technique, the subscribers are power controlled by the base station of their own cell. However, the interference level from subscribers in other cells varies not only according to the attenuation in the path to the subscriber's cell site, but also inversely to the attenuation from the interfering user to his own cell site, which through power control by that cell site may increase or decrease the interference to the desired cell site. It has been shown that the maximal number of subscribers in the cell is the highest when there are no subscribers in the neighboring cells. As the number of subscribers in the neighboring cells increases the maximal number of subscribers in the cell decreases.

Power control for DS-CDMA reverse link is the single most important system requirement because of the Near/ Far effect. In this case, it is necessary to have a dynamic range for control. For the forward link, no power control is required in a single cell system, since all signals are transmitted together and hence vary together. However in multiple cell systems, interference from neighboring cell sites fades independently from the given cell site and thereby degrades performance. Thus it is necessary to apply power control in this case also, to reduce intercell interference.

6

CDMA System Aspects

Fig.4

7

CDMA System Aspects

1.2.3 According to techniques, power control

can be classified as follows: 1. Open-loop power control. 2. Closed-loop power control. 3. Outer loop power control 1. Open-loop power control

Reverse link (mobile to base station) open loop power control is accomplished by adjusting the mobile transmit power so that the received signal at the base station is constant irrespective of the mobile distance; where each mobile computes the relative path loss and compensates the loss by adjusting its transmitting power. The total received power at the cell site is the sum of all powers, which determines the system capacity.

2. Closed-loop power control

Closed-loop power control is accomplished by means of power up or power down command originating from the cell site. A single power control bit is inserted into the forward encoded data stream, the mobile responds by adjusting the power. In order to lower processing delay and to save bandwidth in the forward link, command bits for power control from the base to the mobile station are not coded and they are susceptible to errors.

3. Outer Loop PC

Signal to interference ratio is varied, to guarantee QoS (BER,..)

Fig.5

8

CDMA System Aspects

2 RAKE Receiver

2.1 RAKE Receiver Theory and Structure

A spread-spectrum signal waveform is well matched to the multipath channel. In a multipath channel, the original transmitted signal reflects from obstacles such as buildings, and mountains, and the receiver receives several copies of the signal with different delays. If the signals arrive more than one chip apart from each other, the receiver can resolve them. Actually, from each multipath signal’s point of view, other multipath signals can be regarded as interference and they are suppressed by the processing gain. However, a further benefit is obtained if the resolved multipath signals are combined using RAKE receiver. Thus, the signal waveform of CDMA signals facilitates utilization of multipath diversity. Expressing the same phenomenon in the frequency domain means that the bandwidth of the transmitted signal is larger than the coherence bandwidth of the channel and the channel is frequency selective (i.e., only part of the signal is affected by the fading).

RAKE receiver consists of correlators, each receiving a multipath signal. After despreading by correlators, the signals are combined using, for example, maximal ratio combining. Since the received multipath signals are fading independently, diversity order and thus performance are improved.

After spreading and modulation the signal is transmitted and it passes through a multipath channel, which can be modeled by a tapped delay line (i.e., the reflected signals are delayed and attenuated in the channel).

It is necessary to measure the tapped delay line profile and to reallocate RAKE fingers whenever there is need. Small-scale changes, less than one chip, are taken care of by a code-tracking loop, which tracks the time delay of each multipath signal.

9

CDMA System Aspects

Fig.6

10

CDMA System Aspects

3 Handoff Versus Handover

3.1 Handoff versus Handover The act of transferring support of a mobile from one base station to another is termed

handover or Handoff. It occurs when a call has to be handed over or off from one cell to another as the user moves between cells. In GSM system it is termed hard handoff or Handover where the connection to the current cell is broken, and then the connection to the new cell is made. This is known as a "break-before-make" handoff.

But in a CDMA system the same frequency band is shared between all the cells. Thus there is well-defined efficient bandwidth utilization. Though there is frequency reuse, the orthogonal nature of the waveforms serves to distinguish between the signals that occupy the same frequency band so it is called soft Handover or Handoff.

3.2 Soft Handover

In soft handover a mobile station is connected to more than one base station simultaneously. Soft handover is used in CDMA to reduce the interference into other cells and to improve performance through macro diversity.

3.2.1 The Importance Of Soft Handover

In power controlled CDMA systems soft handoff is preferred over hard handoff strategies. This is more pronounced when the IS-95 standard is considered wherein the transmitter power is adjusted dynamically during the operation. Here the power control and soft handoff are used as means of interference-reduction, which is the primary concern of such an advanced communication system. The previous and the new wideband channels occupy the same frequency band in order to make an efficient use of bandwidth, which makes the use of soft handoff very important. The primary aim is to maintain a continuous link with the strongest signal base station otherwise a positive power control feedback would result in system problems. Soft handoff ensures a continuous link to the base station from which the strongest signal is issued. Soft handoff requires less power, which reduces interference and increases capacity.

11

CDMA System Aspects

Fig.7

3.3 Softer Handover

Is a soft handover between two sectors of a cell. As known that, in a cellular system there is spatial separation between cells using the same frequencies). This is called the frequency reuse concept.

Because of the processing gain, such spatial separation is not needed in CDMA, and frequency reuse factor of one can be used. Usually, a mobile station performs a handover when the signal strength of a neighboring cell exceeds the signal strength of the current cell with a given threshold. Since in a CDMA system the neighboring cell frequencies are the same as in the given cell, this type of approach would cause excessive interference into the neighboring cells and thus a capacity degradation. In order to avoid this interference, an instantaneous handover from the current cell to the new cell would be required when the signal strength of the new cell exceeds the signal strength of the current cell. This is not, however, feasible in practice. The handover mechanism should always allow the mobile station to connect into a cell, which it receives with the highest power (i.e., with the lowest pathloss).

12

CDMA System Aspects

Fig.8

13

CDMA System Aspects

4 Multiuser Detection

The current CDMA receivers are based on the RAKE receiver principle, which considers other users’ signals as interference. However, in an optimum receiver all signals would be detected jointly or interference from other signals would be removed by subtracting them from the desired signal. This is possible because the correlation properties between signals are known (i.e., the interference is deterministic not random).

The capacity of a direct sequence CDMA system using RAKE receiver is interference limited. In practice this means that when a new user, or interferer, enters the network, other users’ service quality will go below the acceptable level. The more the network can resist interference the more users can be served. Multiple access interference that disturbs a base or mobile station is a sum of both intra- and inter-cell interference. Multiuser detection (MUD), also called joint detection and interference cancellation (IC), provides a means of reducing the effect of multiple access interference, and hence increases the system capacity.

In the first place MUD is considered to cancel only the intra-cell interference, meaning that in a practical system the capacity will be limited by the efficiency of the algorithm and the inter-cell interference. In addition to capacity improvement, MUD alleviates the near/far problem typical to DS-CDMA systems. A mobile station close to a base station may block the whole cell traffic by using too high a transmission power. If this user is detected first and subtracted from the input signal, the other users do not see the interference. Since optimal multiuser detection is very complex and in practice impossible to implement for any reasonable number of users, a number of suboptimum multiuser and interference cancellation receivers have been developed. The suboptimum receivers can be divided into two main categories: linear detectors and interference cancellation. Linear detectors apply a linear transform into the outputs of the matched filters that are trying to remove the multiple access interference using too high a transmission power. If this user is detected first and subtracted from the input signal, the other users do not see the interference. Since optimal multiuser detection is very complex and in practice impossible to implement for any reasonable number of users, a number of suboptimum multiuser and interference cancellation receivers have been developed. The suboptimum receivers can be divided into two main categories: linear detectors and interference cancellation. Linear detectors apply a linear transform into the outputs of the matched filters that are trying to remove the multiple access interference (i.e., the interference due to correlations between user codes). Examples of linear detectors are decorrelator and linear minimum mean square error (LMMSE) detectors. In interference cancellation multiple access interference is first estimated and then subtracted from the received signal. Parallel interference cancellation (PIC) and successive (serial) interference cancellation (SIC) are examples of interference cancellation.

14

CDMA System Aspects

Fig.9

15

Appendix

Appendix

1

Appendix A

AC Authentication Center ACCH Associated Control CHannel ACE Antenna Coupling Equipment ADC Analog to Digital Converter AGCH Access Grant Channel AMR Adaptive MultiRate speech AMX ATM MultipleXer AMPS Advanced Mobile Phone Services ANSI American National Standards Institute (USA) AP Application Part ARFCN Absolute Radio Frequency Channel Number ARIB Association of Radio Industries and Business (Japan) ARQ Automatic Repeat reQuest ASCI Advanced Speech Call Items ASN ATM Switching Network ATM Asynchronous Transfer Mode AUC Authentication Center B

BA BCCH Allocation BCC Base transceiver station Color Code BCCH Broadcast Control CHannel BCH Broadcast CHannel BER Bit Error Rate BPSK Binary Phase Shift Keying BS Base Station BSC Base Station Controller BSIC Base transceiver Station Identity Code

Appendix

2

BSS Base Station System BSSAP Base Station System Application Part BSSMAP Base Station System Management Application Part BTS Base Transceiver Station C

CA Cell Allocation CAMEL Customized Applications for Mobile network Enhanced

Logic CATT China Academy of Telecommunication Technology

(China) CC Call Control CC Country Code CCH Control CHannel CCITT Comité Consulatif International Téléphonique et

Télégraphique CCS7 Common Channel signaling System No. 7 CCU Channel Coding Unit CDMA Code Division Multiple Access CEPT Conference Europèene des Postes et

Telecommunication CGI Cell Global Identity CI Cell Identity CN Core Network CP Call Processing CS Coding Scheme CUG Closed User Group CWTS Chinese Wireless Telecommunication Standardization

Institute D

D-AMPS Digital AMPS DCA Dynamic Channel Allocation

Appendix

3

DCS1800 Digital Cellular System in the 1800 MHz band DECT Digital Enhanced Cordless Telephone DL Down Link DoA Direction of Arrival DRNS Drift RNS DRX Discontinuous Reception DS-CDMA Direct Sequence CDMA DSP Digital Signal Processor DTAP Direct Transfer Application Part DTX Discontinuous Transmission DwPTS Downlink Pilot Time Slot E

EDGE Enhanced Data Rates for GSM EFR Enhanced Full Rate speech EIR Equipment Identification Register ERC European Radio communication Committee ERMES European Radio MEssage System ESA European Space Agency ESCD Enhanced Circuit Switched Data ETSI European Telecommunications Standard Institute F

FAC Final Assembly Code FACCH Fast Associated Control CHannel FB Frequency correction Burst FCCH Frequency Correction CHannel FDD Frequency Division Duplex FDMA Frequency Division Multiple Access FEC Forward Error Correction FN Frame Number

Appendix

4

FPLMTS Future Public Land Mobile Telecommunication System FR Frame Relay FR Full Rate speech FRAMES Future RAdio wideband MultiplE access Systems G

GEO GEostationary Orbital GGSN Gateway GPRS Support Node GMM Global Multimedia Mobility GMPCS Global Mobile Personal Communication Systems GMSC Gateway MSC GMSK Gaussian Minimum Shift Keying GP Guard Period GPRS General Packet Radio Service GPS Global Positioning System GSM Global System for Mobile communications H

HCR High Chip Rate HCS Hierarchical Cellular Structures HEO High Elliptic Orbit HLR Home Location Register HO(V) HandOver HR Half Rate speech HPLMN Home PLMN HSCSD High Speed Circuit Switched Data I

IAM Initial Address Message ICO Intermediate Circular Orbits ID IDentification ID IDentity

Appendix

5

IMEI International Mobile Equipment Identity IMSI International Mobile Subscriber Identity IMT-2000 International Mobile Telecommunications-2000 IN Intelligent Network Inmarsat INternational MARitime SATellite ITU International Telecommunication Union IP Internet Protocol IP Intelligent Peripheral ISDN Integrated Services Digital Network ISP Internet Service Provider ISUP ISDN User Part IWE InterWorking Equipment IWF InterWorking Function IWUP InterWorking User Part J

JD Joint Detection JDC Japanese Digital Cellular

K

kbps Kilo Bits per second Kc cipher Key Ki individual subscriber authentication Key L

LA Location Area LAI Location Area Identity LAN Local Area Network LAPDm Link Access Protocol on the Dm channel LCR Low Chip Rate LEO Low Earth Orbital LES Land Earth Station

Appendix

6

LIC Line Interface Circuit LMT Local Maintenance Terminal LR Location Register M

MAP Mobile Application Part MAI Multiple Access Interference MARISAT MARItime SATellite MBS Mobile Broadband System MCC Mobile Country Code Mcps Mega Chips per Second ME Mobile Equipment MExE Mobile station application Execution

Environment MM Mobility Management MMI Man Machine Interface MML Man Machine Language MNC Mobile Network Code MOC Mobile Originating Call MS Mobile Station MSC Mobile services Switching Center MSISDN Mobile Station international ISDN number MSP Multiple Subscriber Profile MSRN Mobile Station Roaming Number MSS Mobile Satellite Systems MT Mobile Termination MTP Message Transfer Part MTC Mobile Termination Call MTP Message Transfer Part MUD Multiuser Detection

Appendix

7

MUX MUltipleXer N

NB Normal Burst NCC Network Color Code (PLMN color code) NDC National Destination Code NE Network Element NMT Nordic Mobile Telephone NSS Network Switching Subsystem O

O&M Operation and Maintenance OACSU Off Air Call Set Up ODMA Opportunity Driven Multiple Access OFDMA Orthogonal Frequency Division Multiple

Access OMC Operation & Maintenance Center OMC-B Operation & Maintenance Center for BSS OMC-S Operation & Maintenance center for SSS OSS Operation SubSystem OVSF Orthogonal Variable Spreading Factor codes P

PA Power Amplifier PACS Personal Access Communication System PC Power Control PCM Pulse Code Modulation PCU Packet Control Unit PDA Personal Data Assistant PDC Personal Digital Cellular (Japan) PDN Packet Data Network PHS Personal Handy System (Japan)

Appendix

8

PIN Personal Identification Number PLMN Public Land Mobile Network PMR Private Mobile Radio PP Point-to-Point PSTN Public Switched Telephone Network Q

QOS Quality Of Service QPSK Quaternary Phase Shift Keying R

RA Rate Adaptation

RACH Random Access CHannel

RAND RANDom number

REQ REQuest

RES RESponse

RF Radio Frequency

RFC Radio Frequency Channel

RFCH Radio Frequency CHannel

RFCN Radio Frequency Channel Number

RNC Radio Network Controller

RNS Radio Network Subsystem

RRM Radio Resource Management

RSS Radio SubSystem

RU Resource Unit

RX / Rx Receiver

S

SACCH Slow Associated Control CHannel SAP Service Access Point SAPI Service Access Point Indicator SB Synchronization Burst

Appendix

9

SCCP Signaling Connection Control Part SCE Service Creation Environment SCH Synchronization CHannel SDCCH Stand- alone Dedicated Control CHannel SF Spreading Factor SFH Slow Frequency Hopping SGSN Service GPRS Support Node SIM Subscriber Identity Module SM Security Management SMG Special Mobile Group SMP Service Management Point SMS Short Message Service SN Subscriber Number SN Switching Network SP Signaling Point SP Switching Point SS Supplementary Services SSF Service Switching Function SSP Service Switching Point STP Signaling Transfer Point SW Software T

T1 Standards Committee T1 Telecommunications TA Terminal Adaptor TAC Type Approval Code TACS Total Access Communication System TB Tail Bit TCAP Transaction CApability Part TCH Traffic CHannel

Appendix

10

TD-CDMA Time Division CDMA TDD Time Division Duplex TDMA Time Division Multiple Access TE Terminal Equipment TETRA TErrestrial Trunked Radio Access THSS Time-Hopping Spread Spectrum TIA Telecommunication Industry Association TMN Telecommunication Management Network TMSI Temporary Mobile Subscriber Identity TRAU Transcoding and Rate Adaptation Unit TRX TRansceiver TS Tele Service TS TimeSlot TTA Telecommunications TechnologyAssociation (South

Korea) TTC Telecommunication Technology Committee (Japan) TX / Tx Transmitter U

UE User Equipment UL UpLink UMTS Universal Mobile Telecommunications System UP User Part USIM UMTS Subscriber Identity Module UTRA UMTS Terrestrial Radio Access UTRAN UMTS Terrestrial Radio Access Network UWC-136 Universal Wireless Communication V

VAD Voice Activity Detection Sprachsteuerung VBR Variable Bit Rate

Appendix

11

VBS Voice Broadcast Service VHE Virtual Home Environment VLR Visited (visitor) Location Register VMSC Visited MSC VoIP Voice over Internet Protocol VPLMN Visited PLMN W

WAN Wide Area Network WAP Wireless Application Protocol WARC World Administrative Radio Conference W-CDMA Wideband CDMA WLL Wireless Local Loop

References

References

1

References

• M. Mouly, M.B. Pautet, "The GSM System for Mobile Communications", Cell & Sys (1992), ISBN 2-9507190-0-7

• S. Redl, M. Weber, K. Oliphant, "An introduction to GSM", Artech House Inc.(1995), ISBN 0-89006-785-6

• Mehrotra, "GSM System Engineering", Artech House Inc. (1997), ISBN 0-89006-860-7

• G. Heine, "GPRS from A – Z", Artech House Inc. (2000), ISBN 1-58053-181-4V.K.G. Garg, K.F. Smolik, J.E. Wilkes, „Applications of CDMA in Wireless/Personal Communications“, Feher / Prentice Hall digital and wireless communications series (1997) ISBN 0-13-572157-1

• A.J. Viterbi: „CDMA: Principles of Spread Spectrum for third Generation Mobile Communication“ (1995), ISBN 0-201-63374-4

• T. Ojanperä, R. Prasad: „ Wideband CDMA for third Generation Mobile Communication“, (1998) ISBN 0-89006-735-X

• R. Prasad, W. Mohr, W. Konhäuser, „Third Generation Mobile Communications Systems, Artech House Publishers (04/2000)

• G. Calhoun, „Third Generation Wireless Communications: Post Shannon Architectures“, Artech House Publishers (07/2000)

• Authentication and Security in Mobile Phones by Greg Rose, Qualcomm Inc., Australia.

• Security in CDMA Wireless Systems by Frank Quick, Qualcomm Inc., February 1997

• Security Aspects of Mobile Wireless Networks, by Mullaguru Naidu, July 2002.

• CDMA RF System Engineering, by Samuel C. Yang • Understanding Cellular Radio, by WILLIAM WEBB • B. J. Wysocki and T. A. Wysocki, “Power Spectra of Signal Formats for

DS-SS CDMA Wireless LANs,” IEEE TENCON, pp. 329-332, 1996 • M.Y. Rhee, CDMA Cellular Mobile Communications Network Security.

Prentice Hall, 1998 • G. Allen and S. Raymond, “Encryption of Analog Signals - A Perspective,”

IEEE Journal on selected area in communications, vol. SAC-2, No. 3, pp. 423-425, 1984.

• James A. Davis, “Security Aspects in Mobile Phone Telephony: Focus on GSM,” White Paper, Jan. 2000.

• CDMA System Analysis II, by Timothy X Brown, Silvana Susi, Sukhjinder Singh University Of Colorado, Boulder

References

2

Useful links

• http://www.3gpp.org • http://www.itu.int/imt • http://www.etsi.fr • http://www.umts-forum.org • http://www.gsmworld.com • http://www.cdg.org

Glossary

Glossary

1

Glossary

AMPS (Advanced Mobile Phone Service): Developed by AT&T’s Bell Laboratories in the1970’s and first used in the US in 1983. The AMPS Standard has been the foundation for the industry in the United States. CDMA (Code Division Multiple Access): Known in the US as IS-95, a spread spectrum approach to digital transmission. With CDMA, each conversation is digitized and then tagged with a code. The mobile phone is then instructed to decipher only a particular code to pluck the right conversation off the air. It has a 1.25Mhz spread spectrum air interface, uses the same frequency bands as AMPS and supports AMPS operation, employing spread-spectrum technology and a special coding scheme. It was adopted by the Telecommunications Industry Association (TIA) in 1993. DAMPS (Digital AMPS): The second generation of the AMPS standard. FDMA (Frequency Division Multiple Access): FDMA is the division of the frequency band allocated for wireless cellular communication into 30 KHz channels, each of which can carry a two way voice conversation. FDMA is the basic technology used in AMPS, the most widely installed cellular phone system in North America. With FDMA, each channel can be assigned to only one user at a time. EDGE (Enhanced Data rate for GSM Evolution): The next generation of data heading towards third generation and personal multimedia environments. It builds on GPRS and is a technique to increase the maximum data capacity of GSM radio channels. It will allow GSM operators to use existing GSM radio bands to offer wireless multimedia IP-based services and applications at theoretical maximum speeds of 384 kbps with a bit-rate of 48 kbps per timeslot and up to 69.2 kbps per timeslot in good radio conditions. GPRS (General Packet Radio Service): A GSM data transmission technique that does not set up a continuous channel from a portable terminal for the transmission and reception of data, but transmits and receives data in packets, with users only paying for the volume of data sent and received. GPS (Global Positioning System): A satellite navigation system, consisting of 24 geosynchronous satellites. Used in personal tracking, navigation and automatic vehicle location technologies.

Glossary

2

GSM (Global System for Mobile communications): A digital cellular or PCS network used throughout the world. Developed by ETSI in Europe. NAMPS (Narrowband AMPS): NAMPS combines cellular voice processing with digital signaling to increase the capacity and functionality of AMPS systems. PCS (Personal Communications Services): A two-way, 1900 MHz digital voice, messaging and data service designed as the second generation of cellular. TDMA (Time Division Multiple Access): A method of digital wireless communications transmission allowing a large number of users to access (in sequence) a single radio frequency channel without interference by allocating unique time slots to each user within each channel UMTS (Universal Mobile Telecommunications System): Europe's approach to standardization for third-generation cellular systems, it will be based on W-CDMA. UMTS will offer a wide range of voice, data and multimedia services with data rates from 114 Kbps to 2 Mbps, depending on whether the user is stationary or in motion. W-CDMA (Wideband Code Division Multiple Access): The European third generation wireless standard. The wideband represents the increase of the frequency band to 5 MHz, in comparison to the 1.25 MHz band used in conventional CDMA (also known as cdmaOne). AuC (Authentication Center): The component of a GSM network that authenticates subscriber and mobile equipment identities. Baseband: The signaling of a digital or analog signal at its original frequencies, i.e. not changed by modulation. BSC (Base Station Controller): The component of a GSM system that controls a group of base stations and acts as a node for connecting base stations to the mobile switching center. BSS (Base Station Subsystem): The combination of BSC’s and base stations that together provide the radio functionality in a mobile system. Cell: The basic geographic unit of a cellular system. Also, the basis for the generic industry term "cellular". The mobile network’s geographic area is divided into smaller “cells”, each of which is equipped with a low-powered radio transmitter/receiver. The cells can vary in size depending upon terrain and capacity demands. By controlling the transmission power, the radio frequencies assigned to one cell can be limited to the boundaries of that cell.

Glossary

3

Cell Site: The central radio transmitter/receiver that maintains communications with mobile phones within a give range. Also called a Base Station. Diversity: The use of multiple antennas to receive or transmit the same signal, so that if one of the antennas picks up a weak signal, another antenna should have a strong signal. Downlink: The transmission of radio signals from the Base Station to the mobile handset. EIR (Equipment Identity Register): The component of a GSM system that retains information about the identity of equipment such mobile phones. Assists network operator in discovering stolen mobile phones and blocking them from using the network. Fading: A reduction in signal strength in a radio signal. Fading is usually caused by reflected waves from the transmitter having different phases from the main signal path. GMSC (Gateway Mobile Switching Center): The component of a GSM network, which provides a point of connection between the GSM network and the PSTN. Handoff: The process of transferring a mobile phone conversation from one cell site to another as a user crosses cell areas during the conversation. HLR (Home Location Register): The component of a GSM network responsible for maintaining the location of a mobile. IMEI (International Mobile Equipment Identity): The unique serial number given to each phone, to help in tracking stolen mobile phones. IMSI (International Mobile Subscriber Identity): A unique number used in GSM systems to identify individual subscribers. MAHO (Mobile Assisted Handoff): Similar to a basic handoff, except that the mobile also helps in finding a suitable base station to handoff into by providing the network with measurements indicating which base station provides the largest signal strength.

Glossary

4

Modulation: Information on a carrier signal modulated by varying one or more of the signal's basic characteristics - frequency, amplitude and phase. Different modulation carries the information as the change from the immediately preceding state rather than the absolute state. MS (Mobile Station): Another name for a cellular mobile phone. MSC (Mobile Switching Center): The switch in a GSM network, which connects calls from the GMSC to the particular base station in which the mobile phone is currently located. The MSC also manages call handovers. MTSO (Mobile Telephone Switching Office): The central computer that connects a wireless phone call to the public telephone network. The MTSO controls the entire system’s operations, including monitoring calls, billing and handoffs. POTS (Plain Old Telephone Service): Standard household phone service. PSTN (Public Switched Telephone Network): The worldwide telephone network which allows people to call anywhere in the world. The PSTN mainly consists of copper cables and switches. Roaming: Roaming allows a user to operate their mobile phone in another countries network. The user’s network makes agreements with other networks worldwide to allow this to happen. Smart antenna: An antenna system with technology that enables it to focus its beam on a desired signal to reduce interference. A wireless network would employ smart antennas at its base stations in an effort to reduce the number of dropped calls, improve call quality and improve channel capacity. Soft handoff: Procedure in which two base stations, one in the cell site where the phone is located and the other in the cell site to which the conversation is being passed, both hold onto the call until the handoff is completed. The first cell site does not cut off the conversation until it receives information that the second is maintaining the call. This reduces the probability of the call being blocked. Uplink: The transmission of radio signals from the mobile handset to the Base Station. VLR (Visitor Location register): The component of a GSM network which keeps track of a mobile phone’s position to the nearest location area.

Glossary

5

Walsh codes: A family of orthogonal codes often preferred for CDMA transmission. WLL Wireless Local Loop: The use of radio to replace copper wiring as a means of connecting the home to the PSTN.



Sub-sections GPRS Introduction

Introduction and Overview

1

GPRS - General Packet Radio Services

2

GPRS Radio Interface

3

Procedures

4

Abbreviations

5

GPRS Introduction


Sub-section identification Pages1 Introduction and Overview 1 - 152 GPRS - General Packet Radio Services 1 - 353 GPRS Radio Interface 1 - 184 Procedures 1 - 105 Abbreviations 1 - 10


Chapter 1


Introduction and Overview Siemens

Contents

1 Mobile Radio Evolution 23

1.1 Trend: from Speech to Data Transmission 34

1.2 The 3rd

Mobile Radio Generation (3G) 46

2 GSM – Current Situation, Services & Applications 69

2.1 GSM – Global System for Mobile Communication 170

2.2 GSM – Implementation in an evolutionary Concept 192

3 GSM – Phase2+ 115

3.1 GSM Phase 2+ Solutions for Meeting Current and Future Mobile

Requirements 126

3.2 Data Transmission in GSM Phase2+ 138

4 Exercise 23

5 Solution 27


1

Introduction and Overview Siemen

1 Mobile Radio Evolution

0,01

0,1

1

10

100

1000

Subscriber[M.]

1982

1984

1986

1988

1990

1992

1994

1996

1998

2000

2002

Year

Germany

World

Subscriber trends:

1982 - 2002

Fig. 1 Increase in the number of subscribers due to introduction of first and second generation of mobile communication

2

1.1 Trend: from Speech to Data Transmission

1G offered mainly speech transmission based on analog transmission modes.

Due to the digital transmission mode it uses, 2G offers not only pure speech trans-

mission but also a number of supplementary services and low rate data transmission.

However, mobile radio systems of 2G are suited optimally to the needs of speech

transmission, primarily; the share of data transmitted via the radio interface will not

exceed 2% even towards the end of the 90ties.

Nevertheless, growth rates in the area of data transmission are much higher than in

the area of speech transmission due to the fact that the need for mobile data trans-

mission is becoming acute in the mobile working world of tomorrow (work outside the

office, teleworking).

Forecasts predict the following figures: in the year 2001, 10% of the total traffic vol-

ume will be allotted to data transport via the radio interface, in 2005 this will already

rise to 30%, and just two years later, in 2007, data transmission will make up 50% of

the total traffic volume and will thus range equal to speech transmission.

Note that there is an underlying rapid increase in the total amount of traffic.


0

20

40

60

80

100

tra

ffic

[%

]

1996 2001 2005 2007

year

speech

data

2 G Trends:

Speech → Data transmission

1 G:

speech transmission only

2 G:

• speech transmission

• supplementary services

• data transmission

Fig. 2 Trend in the traffic to be transported by future mobile communications systems

3

1.2 The 3rd

Mobile Radio Generation (3G)

Currently there are numerous different standards for 1G and 2G mobile radio sys-

tems, each of which has specific characteristics, advantages and disadvantages, ap-

plications and users. Most of the standards are used merely on a national or regional

scale and are not compatible with each other. They cannot meet the requirements

which will be indispensable for future mobile radio systems, such as improved

speech quality, worldwide availability and particularly a fast transfer of large amounts

of data.

3G currently being standardized under the heading IMT-2000 (International Mobile

Telecommunication) designates a global system of compatible standards which in-

deed is able to meet the high demands placed on future mobile radio systems (see

above). The general aim is to enable “communication with anyone, anywhere, any-

time”.

Beside speech transmission, high data rate services and multimedia applications are

to be provided to the customer across all operator-dependent, national and geo-

graphical borders at any place and any time.

The body in charge of IMT-2000 specification is the International Telecommunication

Union ITU. Thus, IMT-2000 shall become the worldwide “guideline” to which all stan-

dards of the 3G orient themselves. In the framework of IMT-2000 guidelines ETSI is

about to standardize a follow-up GSM standard based on the experiences with and

the success of GSM: the standard is known as UMTS (Universal Mobile Telecommu-

nication Standard).

UMTS is a downward compatible to GSM; as such it shall provide worldwide multi-

media access at any point in time and cover all current mobile radio applications.

Data rates of 8 kbit/s up to a maximum of 2Mbit/s shall be supported.

Apart from UMTS the regional standardization authorities draw up further 3G based

on the IMT-2000 guidelines.


4


Third Generation (3G)

2G

Digital Paging

e.g. ERMES

Digital CT

e.g. DECT, PACS, PHS

Wireless

Local Loop

WLL

digital

PMR

e.g. TETRA

digital

cellular systems

e.g GSM, D-AMPS,

IS-95, PDC

digital MSS

e.g. IRIDIUM

1G

analog

Cordless Telephone CT

e.g. CT1, 1+

Paging

Wireless booth

analoge

Private Mobile Radio

PMR

analog

cellular systems


analog MSS

e.g. INMARSAT

IMT-2000:

UMTS, MC-CDMA,

TD-SCDMA,...

3G

Multiple incompatible standards

for different

one standard (family)

for all

• applications

• countries / regions

• applications

• countries / regions

• compatibility within 3G

• downward compatibility to

2G (e.g. UMTS → GSM)

• resource efficiency

• high data rates

• Multimedia

Fig. 3 Intention of third generation as a common global standard for different applications, regions, and service areas

5


2 GSM – Current Situation, Services & Appli-

cations

GSM - current situation,

services & applications

Mobile Radio

Evolution

Fig. 4

6

2.1 GSM – Global System for Mobile Communication

The GSM standard was planned in the early 80ties and agreed upon in 1990 as first

2G standard. The GSM standard has been specified by ETSI as a consistent open

standard for cellular mobile radio systems. It consists of more than 100 recommenda-

tions, categorized into 12 series.

Within Rel. 99 the GSM standard is know specified by GERAN, a group of 3gpp. The

new series are now be found in series number 40-50.

Commercial operation of GSM networks started in 1992. Originally the systems were

planned for Europe only, but in the middle of 1999 there were already 340 GSM net-

works worldwide in 135 countries/regions. In 2001 there are about 45 million sub-

scriber worldwide

Beside the originally planned GSM standard in the 900 MHz range (GSM900 / E-

GSM) further GSM adaptations were specified during the 90ties in the 1800 and 1900

MHz range (GSM1800 & GSM1900) as well as one adaptation for railway communi-

cation (GSM-R).

GSM900 / E-GSM

In 1990 the first GSM standard, known as GSM900 with 2x 25 MHz developed. An

extension of this, the E-GSM (Extended GSM), provides a further 20 MHz, i.e. a total

of 2 x 35 MHz for GSM, in the event that national authorizations to operate other sys-

tems expire.

GSM1800 (DCS1800)

In 1991 the DCS1800 (Digital Cellular System) standard, a GSM adaptation, was

agreed upon as result of a British initiative in view of the opening-up of a mass-

market; in 1997 this standard was renamed GSM1800. For GSM1800 2 x 75 MHz is

available in the 1800 MHz area.

GSM1900 (PCS1900)

Since 1995 PCS1900 (Public Cellular System), renamed GSM1900 in 1997 repre-

sents the GSM adaptation for the American market. 2 x 60 MHz are available for

GSM1900 and other standards (D-AMPS, IS-95,..).

GSM-R

GSM-R (Railway) was specified as GSM Adaption for mobile radio communication. In

1995 ETSI decided to reserve 2 x 4 MHz in 900 MHz range for GSM-R. First GSM-R

systems are in operation since 1998


7


876 880

890

GSM

900

915 921 925

935

960 1710 1785 1805 1850

1880

1910 1930 1990[MHz] [MHz]

GSM

900

E-GSM E-GSM

GSM

1800

GSM

1800

GSM

1900

GSM-RGSM-Adaptations

GSM

1900

Frequency Range

[MHZ]

Useable HF

channels

Application Area

GSM900

E-GSM

890 - 915 / 935 - 960

880 - 915 / 925 - 960

124

174

Worldwide except

US

GSM18001710 - 1785 / 1805 - 1880 374 Worldwide except

US

GSM19001850 - 1910 /1930 - 1990 Shares HF-channels

with other standards

US

GSM-R876 - 880 / 921 - 925 19 European

railroads

Fig. 5 Adaptations of GSM in frequency due to trend to mobile communication

8

2.2 GSM – Implementation in an evolutionary Con-

cept

Originally, the GSM standard was intended as a completed, non-modifiable standard

to be used until the standardization of a 3G follow-up system. However, in 1988 al-

ready it became obvious that it was not possible to standardize all the technical de-

tails and service offers requested within the time frame set. This resulted in the im-

portant decision to leave the GSM standard incomplete and develop and work on it

permanently instead. The evolutionary GSM concept thus provides enough scope for

technical evolutions and can be quickly adapted to the rapidly changing market con-

ditions. GSM developed in various phases.

GSM Phase1

Phase 1 (agreed upon in 1990/91) includes all central prerequisites for mobile, digital

transmission of information. Speech transfer plays an important role. Data transmis-

sion was also defined with transmission rates of 0.3 to 9.6 kbit/s. GSM phase 1 in-

cludes only a few supplementary services.

GSM Phase2

Research on GSM phase 2 was concluded in 1995. Mainly supplementary services

comparable to ISDN were specified, but also technical improvements such as half

rate speech were considered. Of central importance was the agreement on down-

ward compatibility, meaning that all networks and terminal equipment of phase 2

were compatible to the networks and terminal equipment of phase 1.

GSM Phase2+

Phase2+ marks a “smooth” transition as opposed to phase2. The standard is not en-

tirely re-worked. Since 1996 annual releases take place and current themes relate to

new supplementary services relevant mainly for special groups of users, as well as to

connection and call control issues, IN applications and data services with high trans-

mission rates.


9


Phase 1

Phase 2

Phase 1

Phase 2+

Phase 2

Phase 1

Capabilities

year1991 1995 1997

Speech FR,

standard services

Data: max. 9,6 kbit/s

multiple

Supplementary Services (SS)

comparable to ISDN;

decision downward compatibility

Annual Releases !

• new SS

• IN-applications

• new Bearer Services

(high data rates)

GSM: evolutionary concept

Downward compatibility

Early concept:

• closed standard

• life time: until successor standardisation (3G)

Fig. 6 Evolutionary concept of the GSM standard

10


3 GSM – Phase2+

GSM - Phase 2+

Mobile Radio

Evolution

Fig. 7

11

3.1 GSM Phase 2+ Solutions for Meeting Current and

Future Mobile Requirements

GSM phase 2+ develops solutions for numerous demands placed on future mobile

radio systems. Improved speech quality is realized through introduction of a new

speech code (Enhanced Full Rate Speech), worldwide availability is achieved

through multi-mode terminal equipment (satellite roaming). New features (e.g. Ad-

vanced Speech Call Items ASCI for GSM-R) and IN-integration (e.g. Customized Ap-

plications for Mobile network Enhanced Logic, CAMEL) supplement the portfolio of

applications. For the implementation of „mobile Computing“ / Internet access, bearer

services such as High Speed Circuit Switched Data HSCSD, General Packet Radio

Service GPRS are standardized allowing for the adaptation of transmission rates to

those of ISDN. Also, transmission rates can be increased up to 100 kbit/s and more.

User-friendly equipment and comfortable connection options to the mobile equipment

(Blue Tooth) round off the offer and make it suited to meet future demands.

The importance of phase 2+ lies, however, also in the creation of a platform on which

the GSM follow-up standard UMTS can be based. Numerous features of phase 2+

(especially GPRS and CAMEL) are “guidelines” for UMTS and shall prepare UMTS

features. Thus, upward compatibility of GSM with the 3rd

mobile generation is en-

sured and also downward compatibility of UMTS with GSM. To successfully introduce

UMTS this compatibility with GSM as “quasi-world standard” is indispensable, as is

the usage of a common GSM (Phase 2+)/UMTS infrastructure.


EFR

Enhanced

Full Rate

CAMEL

CustomizedApplication

for Mobile network

Enhanced Logic

ASCI

Advanced Speech

Call Items

Multi-

Band / Mode

Satellite

Roaming

GSM

Phase2+

GPRS

General Packet

Radio Service

HSCSD

High Speed Circuit

Switched Data

Multiple further

features

• GSM solutions for

demands to

mobile radio:

∗ enhanced speech quality

∗ user friendly equipment

∗ world-wide connectivity /

“home PLMN” service

∗ specific services

∗ fast transfer of large

data volumes

• platform for UMTS:

compatibility GSM ⇔ UMTS

common infrastructure

GSM

Phase 2+

Solutions

EDGE

Enhanced Data Rates

for the GSM evolution

Fig. 8 Solutions for new demands and market trends offered by GSM phase 2+

12

3.2 Data Transmission in GSM Phase2+

To increase the data transmission rates, in GSM phase 2+ new bearer services with

rates comparable to or higher as ISDN are developed:

HSCSD (High Speed Circuit Switched Data)

GPRS (General Packet Radio Services)

EDGE (Enhanced Data Rates for the GSM Evolution)

High Speed Circuit Switched Data HSCSD

HSCSD (Rec. 02.34) is a circuit switched data service (only point-to-point) for ap-

plications with higher bandwidth demands and continuous data stream, e.g. motion

pictures or video telephony. The higher bandwidth is achieved by combining 1-8

physical channels for one subscriber. Additionally, the data transmission codec was

changed such that a maximum of 14.4 kbit/s instead of 9.6 kbit/s can be transmitted

per physical channel. In this way, HSCSD theoretically enables transmission rates up

to 115.2 kbit/s. In order to implement HSCSD merely the GSM-PLMN software must

be modified. More problematic is the high volume of resources needed.

General Packet Radio Services GPRS

With GPRS it is possible to combine 1-8 physical channel for one user, just as with

HSCSD. Various new coding schemes with transmission rates of up to 21.4 kbit/s per

physical channel enable theoretical transmission rates up to 171.2 kbit/s. Opposite to

HSCSD, GPRS is a packet-switched bearer service, meaning that the same physical

channel can be used for different subscribers. GPRS is resource efficient for applica-

tions with a short-term need for high data rates (e.g. surfing the Internet, E-mail, ...).

GPRS also enables point-to-multipoint transmission and volume dependent charging.

Extensions of the GSM network and protocol architecture are necessary for GPRS

implementation.


13


Comparison HSCSD / GPRS

TDMA-frame ⇔ 8 Time Slots

Time Slot

HSCSD

up to

14.4 kbit/s

GPRS

up to

21.4 kbit/s

HSCSD GPRS

• circuit oriented

⇒ real time applications

(e.g. video telephone)

• bundling of channels

(up to 8 time slots)

• new coding scheme

(9.6 kbit/s → 14.4 kbit/s)

• point-to-point

• small HW modifications

• packet oriented

⇒ data applications

(e.g. internet surfing)

• bundling of channels

(up to 8 time slots)

• 4 new coding schemes

(9.6 kbit/s → 9.05 ... 21.4 kbit/s)

• point-to-multipoint

• new network elements/protocols

Fig. 9 Comparison of HSCSD and GPRS

Enhanced Data rates for the GSM Evolution EDGE

EDGE (Release`99) is able to realize up to 69.2 kbit/s per physical channel though

the change of the GSM modulation procedure (8PSK instead of GMSK). Theoreti-

cally, transmission rates of up to 553.6 kbit/s (meeting 3G requirements) would be

possible by combining up to 8 channels. A combination of GPRS and EDGE could of-

fer optimum usage of Inter- and Intranet, ensuring highest economy in frequency re-

source utilization at the same time.

The change of the modulation method will require hardware changes in the BSS (the

BTS have to be upgraded) and the MS. The mobile equipment has to be small and

cheap but on the other hand high quality linear amplifiers are needed for 8PSK. The

solution to this problem could be that in the introduction phase EDGE is only used in

the downlink.

14


EDGE

(Enhanced Data Rates for GSM Evolution)

EDGE:

• uses a new modulation method:

replaces GMSK by 8PSK

⇒ three bit of information can be transported

by one symbol of modulation (instead of one bit)

⇒ BTS has to be upgraded

⇒ hardware modifications are necessary

• will possibly used only DL in the introduction phase

⇒ cheap mobile phones

⇒ asymmetric data rates in UL and DL

Fig. 10 EDGE replaces GMSK modulation method to enhance data rates

15

Chapter 2

GPRS – General Packet Radio Services

GPRS - General Packet Radio Services Sidemen's

Contents

1 GPRS Objectives and Advantages 23

1.1 GPRS Objectives and Advantages 34

1.2 Standardization 56

2 Basic Principles 79

2.1 Management of Radio Resources/ Coding Schemes 180

2.2 GPRS Subscriber Profile 102

2.3 Quality of Service (QoS) Profiles 124

3 GPRS-Architecture 1721

3.1 GPRS Architecture 1822

3.2 GSM Phase 2+, Interfaces 1924

3.3 New Network Elements for GPRS 216

4 Logical Functions 2735

4.1 Logical Functions in the GPRS Network 2836

4.2 Allocation of Logical Functions 3544

5 Exercises 47

6 Solutions 55

GPRS - General Packet Radio Services

1


1 GPRS Objectives and Advantages

Objectives & Standardization

GPRS

General Packet Radio Services

Fig. 1

2

Sidemen's GPRS - General Packet Radio Services

1.1 GPRS Objectives and Advantages

The transmission of data is becoming increasingly important in the field of telecom-

munication. In the fixed network, the transmission of extensive data files and E-mail

and contacts to the Intra- and Internet is by far in excess of language transmission.

The need for mobile data transport is increasing at a similarly impressive rate, yet the

presently available mobile communication systems, even GSM, still present a num-

ber of shortcomings.

Disadvantages for the user in GSM Phase 1/2:

In GSM (phase 1/2), the data rate is limited to a peak value of 9.6 kbit/s

Links to the data networks need to be routed via PSTN/ISDN (Additional charging of

the user for using a transit network)

The user is billed for the connection duration instead of being billed for his/her actual

use of the network (data volume)

The set-up of a connection takes more time (ca. 20s if a modem is used)

The length of SMS is limited (160 alphanumerical characters)

Disadvantages for the provider in GMS Phase 1/2:

Inefficient resource management & the number of users is limited.

HSCSD (High Speed Circuit Switched Data)

In principle, transmission rates of up to 115.2 kbit/s can be achieved with HSCSD.

Combining 4 timeslots, the ISDN transmission rate can be matched. One problem of

HSCSD, however, is the circuit switched data transmission. Efficient resource man-

agement is impossible. Additional costs arise for the user. For this reason HSCSD is

essentially suited for applications involving high but constant transmission rates

(videotelephony).

GPRS (GENERAL PACKET RADIO SERVICES)

GPRS is, on the one hand, intended to provide the possibility of transmitting large

volumes of data in a very short time. On the other hand it is meant to ensure effective

management of available resources, which will increase the number of users and re-

duce the costs arising for the individual user (volume-oriented fees).

Another positive consequence of the introduction of GPRS is its direct access to the

Intra- and Internet and the possibility to use point-to-point and point-to-multipoint ser-

vices side by side. An important aspect is that GSM networks are prepared for the in-

troduction of UMTS.

3

GPRS - General Packet Radio Services Sidemen'


GPRS Objectives

& Advantages

PSTN

Modem

ISDN

Service provider

access point

BSS

SSS

IP

Modem

SMSC

SMS

PDN´s

Intranet

Internet

PSPDN

BS-udi

BS-

3.1 kHz

audio

GPRS: • high data rates • reducing costs (volume dependent charging)

• resource efficient • Point-to-Multipoint services for PMR market

• no SMS restrictions • direct IP/X.25 connection

• prerequisite for UMTS introduction ⇒ future proof solution

Fig. 2 Limitations of the network architecture

4


1.2 Standardization

The introduction of GPRS into the GSM Recommendations is carried out in two

phases.

Phase 1 of GPRS introduction was completed by ETSI in the Annual Release 1997

(03/98) and includes all central GPRS functions.

Phase 1 supports:

Point-to-point transfer of user data

TCP/IP and X.25 bearer services

GPRS identities

GPRS safety (a new ciphering algorithm specially designed for packet data)

Support of volume-oriented billing

In Phase 2, further extensions are planned for all requirements to be met by GPRS:

Support of point-to multipoint (PTM) services

Support of special point-to-point and point-to-multipoint services for applications such

as traffic telematics and GSM-R (PTM-Group Call: PTM-Multicast)

Support of further additional services

Support of additional interworking functions (e.g. ISDN)

Phase 2 will be completed in 1998 or 1999.

GPRS Phase 1 includes the introduction of a number of new recommendations;

some of the existing recommendations have been modified to cover other GPRS

functions, too.

The following recommendations are of central importance:

Rec. 02.60 General GPRS Overview

Rec. 03.60 GPRS System and architecture description

Rec. 03.64 Radio architecture description

5



GPRS-Standardisation

ETSI/GERAN

GPRS Standardisation in 2 Phases

Rec. 02.60

General GPRS Overview

Rec. 03.60

GPRS system &

architecture description

Rec. 03.64

Radio architecture descriptionVery important:

• PtP Data transmission

• TCP/IP & X.25 Bearer Services

• GPRS Identities

• GPRS Security (Ciphering)

• SMS via GPRS

• volume dependent charging

Phase 1:

(Rel.`97)

• PtM data transmission

• Broadcast & Group Call →

traffic telematic, GSM-R

• further interworking

functionality

• further services

Phase 2:

(Rel.`98/99)

Fig. 3 Standardization of GPRS in phases

6


2 Basic Principles

Basics

GPRS


Fig. 4

7


2.1 Management of Radio Resources/ Coding

Schemes

In a GPRS-supported cell, one or several physical channels can be allocated to

GPRS transmission. These physical channels (Packet Data Channels PDCHs) are

shared by GPRS mobile stations and are taken from the common/shared pool of all

available physical channels of the cell.

Distribution of the physical channels for various logical packet data channels is based

on blocks of 4 normal bursts each. Uplink (UL) and downlink (DL) for GPRS packet

data are assigned separately (consideration of asymmetrical traffic peaks). Allocation

of circuit switched services and GPRS is achieved dynamically, depending on what

capacities are required („capacity on demand“). PDCHs need not be allocated per-

manently; however, it is possible for the operator to permanently or temporarily re-

serve a number of physical channels for GPRS traffic.

New GPRS coding schemes (CS) - CS1 - CS4 - have been defined for the transmis-

sion of packet data traffic channel PDTCH (Rec. 03.64). Coding schemes can be as-

signed as a function of the quality of the radio interface. Normally, groups of 4 burst

blocks each are coded together.

CS-1 makes use of the same coding scheme as has been specified for SDCCH in

GSM Rec. 05.03. It consists of a half rate convolutional code for forward error correc-

tion FEC. CS-1 corresponds to a data rate of 9.05 kbit/s.

CS-4 has no redundancy in transmission (no FEC) and corresponds to a data rate of

21.4 kbit/s.

CS-2 and CS-3 represent punctured versions of the same half rate convolutional

code as CS-1.

CS-2 corresponds to a rate of 13.4 kbit/s, while CS-3 corresponds to a data rate of

15.6 kbit/s.

In principle, 1 to 8 time slots TS of a TDMA frame can be combined dynamically for a

user for the transmission of GPRS packet data. Theoretically it is thus possible to

achieve peak performances of up to 171.2 kbit/s (8x21.4 kbit/s) with GPRS.

8



9,05 kbit/s

13,4 kbit/s

15,6 kbit/s

21,4 kbit/s

CS-1

CS-2

CS-3

CS-4

Coding

Schemes

different

redundancy (FEC) →

“Um transmission quality”

Radio Resource Management / Coding Schemes

CS & PS (GPRS):

“capacity on demand”

Physical channel of one cell

GPRS-MSs:

sharing physical channel

GPRS-MSs:

combining 1-8 TS

Up to

171,2 kbit/s

(theoretically)

1 - 8

channel

GPRS-MSs:

asymmetric UL / DL

Fig. 5 Management of radio resources: coding schemes, FEC, and redundancy

9


2.2 GPRS Subscriber Profile

The GPRS Subscriber Profile is the description of the services a subscriber is al-

lowed to use. Essentially, it contains the description of the packet data protocol used.

A subscriber may also use different packet data protocols (PDPs), or one PDP with

different addresses. The following parameters are available for each PDP:

The packet network address is necessary to identify the subscriber in the public

data net. Either dynamically assigned (temporary) addresses or (in the future) static

addresses are used in case of IP. The problem of the dynamic addresses will be

overcome with the change from Ipv4 to IPv6. In GPRS is two layer 2 protocols are al-

lowed, X.25 or IP.

The quality of service QoS: QoS describes various parameters. The subscriber pro-

file defines the highest values of the QoS parameters that can be used by the sub-

scriber.

The screening profile: This profile depends on the PDP used and on the capacity of

the GPRS nodes. It serves to restrict acceptance during transmission/reception of

packet data. For example, a subscriber can be restricted with respect to his possible

location, or with respect to certain specific applications.

The GGSN address: The GGSN address indicates which GGSN is used by the sub-

scriber. In this way the point of access to external packet data networks PDN is de-

fined. The internal routing of the data is done by IP protocol; the GSNs will have IP

addresses. A DNS function is needed to find the destination of the data packets (ad-

dress translating: e.g. www.gsn-xxx.com → 129.64.39.123)

10



GPRS Subscriber Profile

Subscription profile

used Packet Data Protocols PDP

possible: 1 Subscriber - different PDPs / 1 PDP with different addresses

PDP

Parameter

Packet

network address

static/dynamic

IP address

QoS

Quality of Service

highest QoS-

parameter values in

Subscriber Profile

Screening

Profile

limits receiving / emission

of data packets

GGSN address

Access to external PDN

Fig. 6 Part of the GPRS subscriber profile are the PDPs and their parameters

11


2.3 Quality of Service (QoS) Profiles

The different applications that will make use of packet-oriented data transmission via

GPRS require different qualities of transmission. GPRS can meet these different re-

quirements because it can vary the quality of service (QoS) over a wide range of at-

tributes. The quality of service profile (Rec. 02.60, 03.60) permits selection of the fol-

lowing attributes:

� Precedence class

� Delay class

� Reliability class

� Peak throughput class

� Mean throughput class.

By combining the variation possibilities of the individual attributes a large number of

QoS profiles can be achieved. Only a limited proportion of the possible QoS profiles

need PLMN-specific support.

Quality of Service QoS - Profile

Different requirements for different applications ⇒

multiple GPRS QoS profiles

precedence class

delay class

reliability class

Peak

throughput

class

mean throughput

class

PLMN must support only

limited QoS service profile

Fig. 7 Quality of service parameters

12



Precedence Class

Three different classes have been defined to allow assessment of the importance of

the data packets, in case of limited resources or overload:

1. High precedence

2. Normal precedence

3. Low precedence

Delay Class

GSM Rec.02.60 defines 4 delay classes (1 to 4). However, a PLMN only needs to re-

alize part of these. The minimum requirement is the support of the so-called „best ef-

fort delay class“ (Class 4). Delay requirements (maximum delay) concern the delay of

transported data through the entire GPRS network (the first two columns refer to data

packets 128 bytes in length, while the last two columns apply to packets 1024 bytes

in length).

Delay Class mean transfer

delay (sec)

95% delay

(sec)

mean transfer

delay (sec)

95% delay

(sec)

1 < 0,5 < 1,5 < 2 < 7

2 < 5 < 25 < 15 < 75

3 < 50 < 250 < 75 < 375

4 (Best Effort) unspecified unspecified unspecified unspecified

13




Precedence Class

1: high priority

2: normal priority

3: low priority

Delay Class mean transfer

delay (sec)

95% delay

(sec)

mean transfer

delay (sec)

95% delay

(sec)

1 < 0,5 < 1,5 < 2 < 7

2 < 5 < 25 < 15 < 75

3 < 50 < 250 < 75 < 375

4 (Best Effort) unspecified unspecified unspecified unspecified

Delay Class

SDU size: 128 Byte 1024 Byte

minimum

requirements

Fig. 8 QoS is an assumption of several parameters, which are defined in the recommendations

14


Reliability Class

Transmission reliability is defined with respect to the probability of data loss, data de-

livery beyond/outside the sequence, twofold data delivery, and data falsification

(probabilities 10-2

to 10-9

):. 5 reliability classes (1 to 5) have been defined, 1 guaran-

teeing the highest and 5 the lowest degree of reliability. Highest reliability (Class 1) is

required for error-sensitive, non-real-time applications, which have no possibility of

compensating for data loss; lowest reliability (Class 5) is needed for real-time applica-

tions which can get over data loss.

Peak Throughput Class

The peak throughput class defines the maximum data rate to be expected (in

bytes/s). However, there is no guarantee that this data rate/throughput can be

achieved over a certain period of time. This depends on the capacity of the MS and

the availability of radio resources. 9 throughput classes have been defined, ranging

from Class 1 with 1000 bytes/s (8 kbit/s) to 256,000 bytes (2048 kbit/s). The maxi-

mum data rate doubles from one class to the next.

Mean Throughput Class

The mean throughput class represents the mean data rate /throughput to be ex-

pected for data transport via the GPRS network during an activated link. A total of 19

classes have been defined. Class 1 is „best effort“ and means that the data rate for

the MS is made available on the basis of demand and availability of resources.

Class 2 stands for 100 bytes/h (0.22 bit/s), class 3 for 200 bytes/h, class 4 for 500

bytes/h and class 5 for 1000 bytes/h, etc. till Class 19 which stands for 50000000

bytes/h (111 kbit/s).

15




Reliability Class

1 - 5 (lowest):

• data loss probability

• out of sequence probability

• duplicate probability

• corrupt data probability

probabilities 10-9

- 10-2

peak throughput Class

1 - 9: > 8 kbit /s - >2048 kbit /s

maximum data rate

no guarantee for this data rates

over a longer period of time

mean throughput Class

medium, guaranteed data rate; Class 1-19

1: best effort

100 Byte/h (0,22 bit/s) / 200 / 500 / 1000 / ... /

50 Mio. Byte/h (111 kbit/s)

Fig. 9 QoS is an assumption of several parameters, which are defined in the recommendations

16


3 GPRS-Architecture

Architecture

GPRS


Fig. 10

17


3.1 GPRS Architecture

For introducing GPRS, the logical GSM architecture is extended by two functional

units:

The Serving GPRS Support Node SGSN is on the same hierarchic level as MSC

and has functions comparable to those of a Visited MSC (VMSC).

The Gateway GPRS Support Node GGSN has functions comparable with those of a

Gateway MSC (GMSC) and offers interworking functions for establishing contact be-

tween the GSM/GPRS-PLMN and external packet data networks PDN

A GPRS Support Node GSN includes the central functions required to support the

GPRS. One PLMN can contain one or more GSNs.

In addition to GSN, extensions of functions in other GSM functional units are neces-

sary:

In the BSS a Packet Control Unit PCU ensures the reception/adaptation of packet

data from SGSN into BSS and vice versa.

GPRS subscriber data are added to the HLR. On the following pages of this script

this extension will be termed GPRS Register GR.

Channel Codec Unit CCU

in BTS

for channel coding

Mobile

DTE

SGSN

Serving GPRS

Support Node

PSTN

Internet

Intranet

X.25

GGSN

Gateway GPRS

Support Node

VMSC /

VLR

GMSC

HLR

New network entities:

• SGSN

(access to BSS)

• GGSN

(access to PDN)

GPRS - Architecture

ISDN

PCU

BSS

GPRS subscription data

(GPRS Register GR)

Packet Control Unit PCU

for

protocol conversion &

radio resource

management

Fig. 11 Outline of the GPRS architecture

18



3.2 GSM Phase 2+, Interfaces

Integration of functions GGSN and SGSN (which are necessary for GPRS) into a

GSM-PLMN makes it necessary to provide names for a series of new interfaces in

addition to interfaces A-G already defined in the GSM-PLMN:

Gb - between an SGSN and a BSS; Gb allows the exchange of signaling and user

data: Unlike the A-interface, in which a user is assigned a certain physical resource

for the entire/full duration of a connection, on Gb a resource is only assigned in case

of activity (i. e. when data are being transmitted/received). A large number of sub-

scribers use the same physical resources. The same holds for interfaces Gi, Gn and

Gp.

Gc - between a GGSN and an HLR

Gd - between an SMS-GMSC / SMS-IWMSC and an SGSN

Gf - between an SGSN and an EIR

Gi - between GPRS and an external packet data network PDN

Gn - between two GPRS support nodes GSN within the same PLMN

Gp - between two GSN located in different PLMNs. The Gp interface allows the sup-

porting of GPRS services over an area of cooperating GPRS PLMNs.

Gr - between an SGSN and an HLR

Gs - between an SGSN and an MSC/VLR; serves to support an MS using both

GPRS and circuit switched services (e.g. update of location information).

19



PSTN

X.25

Common GSM/GPRS/UMTS Network:

Interfaces, Network Elements

ISDN

IP

IWF/TC: Interworking Function / Transcoder

IWF/

TC

A

Gb

Iu(PS)

Gi

GMSC

GGSN

GSM Phase 2+

Core Network

MSC

SGSN

HLR/ACEIRCSE

Iu(CS)

A

Gn

T

R

A

U

B

S

C

BTS

BTS

Abis

UE

(USIM)

Uu

Um

MS

(SIM)

E

SMS-GMSC

SMS-IWMSC

EG

d

GSM BSS

Asub

Gs

Gr G

c

UMTS

Terrestrial

Radio

Access

Network

Gf

VLR

SLR

Fig. 12 Common GSM/GPRS/UMTS core network, coexistence of two radio access networks (GSM BSS/UTRAN)

20


3.3 New Network Elements for GPRS

3.3.1 Serving GPRS Support Node (SGSN) Functions

SGSN realizes a large number of functions for performing GPRS services.

SGSN is on the same hierarchic level as an MSC and handles many functions com-

parable to a Visited MSC (VMSC).

SGSN

is the node serving GPRS mobile stations in a region assigned to it;

traces the location of the respective GPRS MSs (Mobility Management functions);

is responsible for the paging of MS;

performs security functions and access control (authentication/cipher setting proce-

dures,...) Procedures are based on the same algorithm, ciphers and criteria as in the

former GSM. Ciphering algorithms have been optimized for the transmission of

packet data;

has routing/traffic-management functions;

collects data connected with fees/charges;

realizes the interfaces to GGSN (Gn), PCU (Gb), other PLMNs (Gp), HLR (Gr),

VLR (Gs), SMS-GMSC (Gd), EIR (Gf).

3.3.2 Gateway GPRS Support Node (GGSN) Functions

GGSN realizes functions comparable to those of a gateway MSC.

GGSN

� is the node allowing contact/interworking between a GSM PLMN and a packet

data network PDN (realization Gi-interface);

� contains the routing information for GPRS subscribers available in the PLMN.

Routing information serves to contact the respective SGSN in the providing area of

which an MS is momentarily located;

� has a screening function;

� can inquire about location informations from the HLR via the optional Gc interface

� transfers data/signaling to SGSN via Gn interface.

21



GGSN

SGSN & GGSN

SGSN

Serving GPRS Support Node SGSN

• serves MSs in SGSN area

• Mobility Management functions, e.g

Update Location, Attach, Paging,..

• Security and access control:

Authentication, Cipher setting, IMEI Check...

New cipher algorithm

• Routing / Traffic-Management


• realises Interfaces: Gn, Gb, Gd, Gp, Gr, Gs, Gf

• controls subscribers in its service area (SLR)

Gateway GPRS Support Node GGSN

• Gi-,Gn-Interface: Interworking PLMN ↔ PDN

• Routing Information for attached GPRS user

• Screening / Filtering


• optional Gc interface

Fig. 13 Tasks of GGSN and SGSN

22


3.3.3 Physical Realization SGSN/GGSN

SGSN and GGSN functions, respectively, can be located within the same physical

unit or at different locations in different physical units. SGSN and GGSN include the

internet protocol (IP) routing function and can be linked together/Interconnected with

IP routers (IP-based GPRS backbone network for Gn). The same holds for the Gp in-

terface (SGSN and GGSN in different PLMNs); in addition there are safety functions

for inter-PLMN communication.

HLR (GPRS Register GR)

HLR includes the GPRS subscriber information (GPRS Register GR) and routing in-

formation. Access to HLR is possible from SGSN via Gr and from GGSN via Gc inter-

face.

SGSN & GGSN:

physical location

External

IP Network

GGSN

SGSN

HLR (GR)

BSSPCU

GPRS-MS

MSC/VLR

BSSPCU

HLR:

• GPRS subscriber data

(GPRS Register GR)

• Routing information

Gb

Gb

Gi

GrGs

SGSN & GGSN

in same

physical entity

SGSN

GGSN

SGSN

GGSN

GGSN

BSSPCU

GPRS-MS

BSSPCU

External

X.25 Network

IP-based

Backbone

Network

Gn

Gp

Security functions

for Inter-PLMN

communication

other

PLMN

SGSN & GGSN

in different

physical entities /

location

External

IP Network

Fig. 14 Different physical locations of SGSN and GGSN

23



3.3.4 Packet Control Unit PCU

In the BSS, the PCU serves

for the management of GPRS radio channels (Radio Channel Management func-

tions), e.g. power control, congestion control, broadcast control information

for the temporal organization of the packet data transfer for uplink and downlink

it has channel access control functions, e.g. access request and grants

it serves for converting protocols from the Gb interface to the radio interface Um.

Three options for positioning the PCU are provided in Rec. 03.60:

Option A: In the BTS

Option B: in the BSC

Option C: In spatial connection with the SGSN

The different positions may be used due to the different solutions of the vendors and

with regard to the traffic, which has to be handled by the PCU/BSS.

3.3.5 Channel Codec Unit CCU

The CCU contains the following functions:

Channel coding, including forward error correction FEC and interleaving

Radio channel measurements, including received quality and signal level, timing ad-

vance measurements

24



CCU

CCU

PCU

BTS BSC site GSN site

CCU

CCU


CCU

CCU


PCU

PCU

A

B

C

optional:

PCU-locationPCU, CCU, GPRS - MS

Um Abis

Gb

MS

MS

MS

Packet Control Unit PCU

• Channel Access Control functions

• Radio Channel Management functions

(Power Control, Congestion Control,...)

• scheduling data transmission (UL/DL)

• protocol conversion (Gb ↔ Um)

Gb

Channel Codec Unit CCU

• Channel Coding (FEC, Interleaving,..)

• Radio Channel Measurementfuncions

(received quality & signal level, TA,..)

Fig. 15 Positioning of the new network elements in the GSM BSS

25


3.3.6 GPRS Mobile Stations MS

A GPRS MS can work in three different operational modes. The operational mode

depends on the service an MS is attached to (GPRS or GPRS and other GSM ser-

vices) and on the mobile station’s capacity of simultaneously handling GPRS and

other GSM services.

„Class A“ operational mode: The MS is attached to GPRS and other GMS services

and the MS supports the simultaneous handling of GPRS and other GSM services.

„Class B“ operational mode: The MS is attached to GPRS and other GMS services,

but the MS cannot handle them simultaneously.

„Class C“ operational mode: The MS is attached exclusively to GPRS services.

Note: Various GSM specifications use the terms GPRS Class-A MS, GPRS Class-B

MS, GPRS Class-C MS.

GPRS-Mobile Station

Class A

Simultaneously handling

of GPRS and other

GSM services

Class B

GPRS and GSM

services but not

simultaneously

Class C

Only GPRS services

Fig. 16 GPRS mobile stations

26



4 Logical Functions

Logical Functions

GPRS


Fig. 17

27


4.1 Logical Functions in the GPRS Network

The tasks required for the handling of processes in the GSM-/GPRS network are

structured into logical functions. These functions may contain a large number of indi-

vidual functions. Logical functions are:

� Network access control functions

� Packet routing and transfer functions

� Mobility management functions

� Logical link management functions

� Network management functions.

Logical functions

in GPRS networks

Network Access

Control

Functions

Mobility

Management

Functions

Radio Resource

Management

Functions

Packet Routeing

& Transfer

Functions

Logical Link

Management

Functions

Network

Management

Functions

Fig. 18 Logical functions of the GPRS network

28



4.1.1 Network Access Control Functions

Network access means the way or manner in which a subscriber gains access to a

telecommunication network to make use of the services this network provides. An

access protocol consists of a defined set of procedures, which makes access to the

network possible. Network access can be obtained both from the MS and from the

fixed network part of the GPRS network. Depending on the provider, the interface to

external data networks can support various access protocols, e.g. IP or X.25. The fol-

lowing functions have been defined for access to the GPRS network:

Registration function: Registration stands for linking the identity of the mobile radio

subscriber to his packet data protocol (or protocols), the PLMN-internal addresses

and the point of access of the user to external data Protocol (PDP) networks. This

link can be static (HLR entry), or it can be effected on demand.

Authentication and authorization function: This function stands for the identifica-

tion of the subscriber and for access legitimacy when a service is demanded. In addi-

tion, the legitimacy of the use of this particular service is controlled. The authentica-

tion function is carried out in conjunction with the mobility management functions.

Admission control function: Admission control is intended for determining the net-

work resources required for performing the desired service (QoS). It also decides

whether these resources are available, and lastly it is used for reserving resources.

Admission control is effected in conjunction with the radio resource management

functions to enable assessment of radio resources requirements in each individual

cell.

Message screening function: A "screening" function is combined with the filtering of

unauthorized or undesirable information/messages. In the introduction stage of

GPRS a network-controlled screening function is supported. Subscription-controlled

and user-controlled screening may be additionally provided at a later stage.

Packet terminal adaptation function: This function adapts data packets re-

ceived/transmitted from/to the terminal equipment TE to a form suited for transport

through the GPRS network.

Charging data collection function: This function is used for collecting data required

for billing

29



Network Access Control Function

Registration:

User‘s mobile ID associated with

*user‘s PDP

*address

*access points

Authentication &

Authorisation

*user

*requested services

Admission Control

*required resources

(available resouces)

(reservation of resources)

Message Screening

Filters unsolicited and

unauthorised messages

Packet Terminal Adaption

Adaption of data packets

between

MS-TE and GPRS-network

Charging Data Collection

Subscription fees + traffic fees

Fig. 19 Network access control functions

30


4.1.2 Packet Routing and Transfer Functions

A route consists of an orderly list of nodes used for the transfer of messages within

and between the PLMNs. Each route consists of the node of origin, no node, one or

several relay nodes, and the node of destination. Routing is the process of determin-

ing and using the route for the transmission of a message within or between PLMNs.

Relay function: Transferring data received by a node from another node to the next

node of the route.

*Routing function: Determining the transmission path for the next hop on the route

towards the GPRS support node (GSN) the message is intended for. Data transmis-

sion between GSNs can be effected via external data networks possessing their own

routing functions; e. g. X.25, Frame Relay or ATM networks.

Address translation and mapping function: Address translation means transforming

one address into another, different address. It can be used to transform addresses of

external network protocols into internal network addresses (for routing purposes).

Address mapping is used to copy a network address into another network address of

the same type (e.g. for the routing and transmitting of messages from one network

node to the next).

Encapsulation function: Encapsulation means supplementing address- and control in-

formation into one data unit for the routing of packets within or between PLMNs. The

opposite process is called decapsulation. Encapsulation and decapsulation is ef-

fected between the GSN of the GPRS-PLMN as well as between the SGSN and the

MS.

Tunneling Function: Tunneling means the transfer of encapsulated data units in the

PLMN. A tunnel is a two-way point-to-point path, only the endpoints of which are

identified.

Compression function: for the optimal use of radio link capacity.

Ciphering function: preventing eavesdropping

Domain name server function: Decoding logical GSN names in GSN addresses. This

function is a standard function of the internet.

31



Packet Routing & Transfer Function

Relay

forward data packetsRouting

„next hop“

Address Mapping

&Translation

Encapsulation

Tunneling

Compression

Ciphering Domain Name

Server

Fig. 20 Packet routing and transfer functions in the GPRS network

32


4.1.3 Mobility Management Functions

Mobility management functions are used to enable tracing the actual location of a

mobile station in either the home-PLMN or a Visited-PLMN.

4.1.4 Logical Link Management Functions

Logical link management functions concern maintenance of a communication chan-

nel between an MS and the PLMN via the radio interface Um. These functions in-

clude the coordination of link state information between the MS and the PLMN and

the monitoring of data transfer activities via the logical link.

Logical link establishment function: Building up a logical link by during GPRS at-

tach.

Logical link maintenance function: Monitoring of the state of the logical link and

state modification control.

Logical link release function: De-allocation of resources associated with the logical

link.

4.1.5 Radio Resource Management Functions

Radio resource management functions include allocation and maintenance of com-

munication channels via the radio interface. The GSM radio resources must be di-

vided /distributed between circuit switched services and GPRS.

Um management function: Managing available physical channels of cells and de-

termining the share of radio resources allocated for use in the GPRS. This share may

vary from cell to cell.

Cell selection function: Allows the MS to select the optimal cell for a communication

path. This includes measurement and evaluation of the signal quality of neighboring

cells and detection and avoidance of overload in the eligible cells.

Um-tranx function: Offers capacity for packet data transfer via Um. The function in-

cludes a. o. procedures for multiplexing packets via shared physical channels, for re-

taining packets in the MS, for error detection and correction, and for flow control.

Path management function: Management of packet data communication between

BSS and serving GSN node. Establishing and canceling these paths can be effected

either dynamically (amount of traffic data) or statically (maximum load to be expected

for each cell).

4.1.6 Network Management Functions

Network management functions provide mechanisms for the support of GPRS-

related operation & maintenance functions.

33



Maintenance of communication channel,

co-ordination Link state information & supervision of

data transfer activity over the logical link MS - SGSN

• Logical Link Establishment

• Logical Link Maintenance

• Logical Link Release

Keep track of current MS-location

Mobility Management Functions

Allocation & maintenance of radio communication path

• Um Management: manage resources GPRS / non GPRS

Cell Selection:select optimal cell (by MS)

• Um-tranx: MAC via Um, user multiplexing, packet discrimination

within MS, error detection & correction, flow control procedures

• Path Management:

manages packet data communication

BSS↔SGSN

(dynamic → data traffic or static)

Radio Resource

Management Functions

mechanism to support O&M

functions related to GPRS

Network Management

Functions

Logical Link

Management Functions

Fig. 21 Mobility management, logical link, radio resource and network management functions

34


4.2 Allocation of Logical Functions

The tasks described in the logical functions can be allocated to various functional

units of the GSM-/GPRS network. The mobile station MS, the base station subsys-

tem BSS (with the packet control unit PCU and channel codec unit CCU), the serving

GPRS support node SGSN and the gateway GPRS support node GGSN participate

in handling the following functions:

Function MS BSS SGSN GGSN HLR

Network Access Control:

Registration X

Authentication & Authorization X X X

Admission Control X X X

Message Screening X

Packet Terminal Adaptation X

Charging Data Collection X X

Packet Routing & Transfer:

Relay X X X X

Routing X X X X

Address Translation & Mapping X X X

Encapsulation X X X

Tunneling X X

Compression X X

Ciphering X X X

Domain Name Server X

Mobility Management X X X X

Logical Link Management:

Logical Link Establishment X X

Logical Link Maintenance X X

Logical Link Release X X

Radio Resource Management:

Um Management X X

Cell Selection X X

Um-Tranx X X

Path Management X X

35


Chapter 3


GPRS Radio Interface Siemens

Contents

1 The Radio Interface (Layer 1) 23

1.1 Layer 1 of the GSM-/GPRS-Radio Interface Um 34

1.2 Channel Bundling, Sharing of Channels 56

1.3 Radio Block 78

1.4 Coding Schemes: 190

1.5 Logical GPRS Radio Channels 134

1.6 Multiframes in GPRS 178

2 Exercises 21

3 Solutions 25


1


1 The Radio Interface (Layer 1)

The Radio Interface Um

(Layer 1)

GPRS:

Interfaces

Fig. 1

2

1.1 Layer 1 of the GSM-/GPRS-Radio Interface Um

By introducing GPRS services into the GSM-PLMN, worldwide modifications are

necessary also in the area of physical transmission (layer1) via the air or radio inter-

face Um. The tasks of layer 1 radio interface relate to the transmission of user and

signaling data as well as to the measuring of receiver performance, cell selection, de-

termination and updating of the delayed MS transmission (timing advance TA), power

control PC and channel coding.

In the GPRS, a decisive difference to the realization of the connection-oriented ser-

vices (circuit-switched services) relates to the fact that a physical channel and a so-

called packet data channel can be used by several mobile stations at the same time.

One packet data channel is allocated per radio block, i.e. for four consecutive TDMA

frames and not for a specific time interval. This means that signaling and the packet

data traffic of several mobile stations can be statistically multiplexed into one packet

data channel. Furthermore, the packet data channel can be seized asymmetrically.

On the other hand it is also possible for a mobile station to use more than one packet

data channel at the same time, i.e. to combine several physical channels of one radio

carrier. In principle, up to 8 packet data channels can be seized simultaneously. The

number of channels that are combined for reception (DL) and transmission (UL) can

be different to achieve asymmetric data rates for certain applications (e.g. file transfer

protocol FTP, internet surfing).

The assignment of radio resources can be done dynamically or in a fixed allocation.

In case of the fixed allocation a message with a bit pattern is sent downlink to indi-

cate which channels can be used by this MS for UL transmission.

If dynamic allocation is applied the MS will be receive a temporary flow identifier (TFI)

and an uplink state flag (USF) for each of the time slots it is allowed to use. The TFI

is part of the control information in the DL packet and identifies the "owner" of the

packet. Each packet also includes an USF that indicates which of the MSs (that has

been assigned to use this time slot UL) is allowed to transmit the next radio block UL.

GPRS Radio Interface Siemen

3


GSM RF:

GPRS Layer 1 (Um)

L1-

tasks

Transmission

of user &

signaling data

determinate &

actualise

Timing Advance

Cell Selection

Measure

signal strength

Power Control

functions Resource optimization:

1 physical channel to be used

by many MSs simultaneously !!

asymmetrical traffic

UL / DL possible !!

High data rate traffic

up to 171.2 kbit/s:

combining 1..8 PDCH for 1 MS !!

Allocation of physical channel

(Packet Data Channel PDCH)

dynamically: 1 or 4 Radio Blocks

(1 Radio Block = 4 Normal Burst

in 4 consecutive TDMA-frames)

⇒ User & signaling data of several MSs

statistically to be multiplexed into 1 PDCH

(also fixed allocation possible)29 multislot classes

Fig. 2 Tasks of the GSM air interface, layer 1 (GSM RF)

4

1.2 Channel Bundling, Sharing of Channels

Sharing of Resources in a Cell: GSM circuit switched (CS) users will share the time

slots in a BTS with the GPRS packet switched (PS)users. A physical channel can ei-

ther be used for GSM CS or GPRS PS traffic but not for both at the same time. De-

pending on the traffic load in the cell there will be more or less channels available for

GPRS, CS connections are dealt with priority.

Sharing of Physical Channels: It is a characteristic of a CS connection that the

physical resource (the time slot) is reserved for one subscriber. Therefore the

GSM CS users cannot share their channels with others. In contrast GPRS PS sub-

scribers can share physical channels. The handling of the channels, the multiplexing

of subscribers onto the same time slots is done by software (protocol, MAC) and

hardware (PCU). Packet oriented connections are not only carried out through the

core network by usage of an appropriate hardware (ATM switches) and software

(protocols) but also on the air interface. This is an important feature of GPRS with re-

gard to an optimized usage of resources on Um, which is the limiting bottleneck in the

PLMN.

Multislot Classes: The subscribers for GPRS will have different needs (applications,

data rates) and therefore the MS will have more or less capabilities. The network

(PCU) will have to identify these different MSs by their multislot class, which indicates

how many time slots (channels) can be bundled by the MS uplink and downlink. A

cheap GPRS mobile will be a GSM mobile that is able to handle the protocols and

coding schemes of GPRS. This will be multislot class 1: one time slot UL and one

time slot downlink can be "bundled". The other extreme is multislot class 29 which

will be able to receive and to transmit in eight time slots UL and DL simultaneously. In

consequence such a MS has to have two synthesizers, and a high battery capacity

because this is more or less continuous transmission and reception. The MS will

send its multislot class and the PCU will only assign time slot combinations which can

be handled by this equipment.


5


Channel Bundling, Sharing of Channels

Radio Blocks

Subsriber A

Radio Blocks

Subscriber B

Radio Blocks

Subscriber C

Radio Block

Subscriber D

TS 0 TS 1 TS 2 TS 3 TS 4 TS 5 TS 6 TS 7 TS 0 TS 1 TS 2 TS 3 TS 4 TS 5 TS 6 TS 7

UL DL

Fig. 3 Channel bundling, sharing of channels

6

1.3 Radio Block

Channel coding was modified substantially for GPRS purposes (GSM Rec. 03.64).

Channel coding starts with the division of digital information into transferable blocks.

These radio blocks, i.e. the data to be transferred (prior to encoding) comprise:

� a header for the Medium Access Control MAC (MAC Header)

� signaling information (RLC/MAC Signaling Block) or user information (RLC Data

Block) and

� a Block Check Sequence BCS.

The functional blocks (radio blocks) are protected in the framework of convolutional

coding against loss of data. Usually, this means inserting redundancy.

Furthermore, channel coding includes a process of interleaving, i.e. different ar-

rangement in time. The convolutional radio blocks are interleaved to a specific num-

ber of bursts/burst blocks. In the case of GPRS, interleaving is carried out across four

normal bursts NB in consecutive TDMA frames and, respectively, to 8 burst blocks

with 57 bit each.

Four new coding schemes were introduced for GPRS (Rec. 03.64): CS-1 to CS-4.

These can be used alternatively depending on the information to be transferred and

on the radio interface’s quality.


7


Radio Block Strucure

collect

user data

signaling

Radio Block

RLC Data Block BCSMAC Header

RLC/MAC Control Block BCSMAC Header

BCS: Block Code Sequence

(for error recognition)

MAC: Medium Access Control RLC: Radio Link Control

One Radio Block = 4 normal bursts

Fig. 4 Radio block

Convolutional

coding

(not CS-4)

Radio Block

Radio Block

(Redundancy !)

rate 1/2 convolutional coding

Radio Block (456 Bits)

puncturingPuncturing

(only CS-2, CS-3)

Interleaving 57 Bit8 Burst-

blocks

57 Bit 57 Bit 57 Bit57 Bit•••

Channel Coding

4 new Coding Schemes:

CS-1, -2, -3, -4

Um: Allocation of PDCH for 1 / 4 Radio Blocks = 4 / 16 Normal Bursts

Fig. 5 Channel coding schemes

8

1.4 Coding Schemes:

CS-1: CS-1 uses the same coding scheme as specified by Rec. 05.03 for the

SDCCH. It comprises a half rate convolutional code for FEC forward error correction.

CS-1 corresponds to a data rate of 9.05 kbit/s.

CS-2 and CS-3 are punctured version of the same half rate convolutional code as

CS-1. The coded bits are numbered starting from 0 and certain punctured bits are

removed.

CS-2: With CS-2 the punctured bits have numbers 4 ∗ i + 3 with i = 3,...,146 (excep-

tion: i = 9, 21, 33, 45, 57, 69, 81, 93, 105, 117, 129, 141). This means that none of

the first 12 bits is punctured. CS-2 corresponds to a data rate of 13.4 kbit/s. Remark:

For CS-2 the puncturing pattern must be adapted to the future new TRAU frame for-

mat in order to be used via the Abis interface (e.g. more bits must be punctured to

make space for RLC signaling).

CS-3: With CS-3 the punctured bits have numbers 6 ∗ i + 3 and 6 ∗ i + 5 with i =

2,...,111. CS-3 corresponds to a data rate of 15.6 kbit/s.

CS-4: CS-4 has no redundancy (no FEC) and corresponds to a data rate of 21.4

kbit/s.

By bundling up to 8 packet data channels of one carrier into one MS, transmission

rates up to 171.2 kbit/s are possible.


9


9,05 kbit/s 13,4 kbit/s 15,6 kbit/s 21,4 kbit/s

CS-1 CS-2 CS-3 CS-4 Different

Redundancy

(FEC)

Quality Um→

Coding

Scheme

Code

Rate

Radio

Block*

Coded

Bits

Punctured

Bits

Data Rate

kbit/s

CS-1 1 / 2 181 456 0 9,05

CS-2 ≈ 2 / 3 268 588 132 13,4

CS-3 ≈ 3 / 4 312 676 220 15,6

CS-4 1 428 456 0 21,4

Channel Coding: Coding Schemes

* Radio Block without

Uplink State Flag USF &

Block Check Sequence BCS

Fig. 6 Coding schemes of GPRS, CS1 with high redundancy, CS4 no redundancy, radio blocks

10

GPRS Channel Coding

Existing channel coding procedures have been modified with a view to introducing

the GPRS. New coding schemes CS 1-4 were specified from ETSI 4. Basically, they

make it possible to transmit 9.05 kbit/s (CS-1), 13.4 kbit/s (CS-2), 15.6 kbit/s (CS-3)

and 21.4 kbit/s (CS-4) per timeslot, respectively.

On the Abis interface, transport capacity is restricted to 16 kbit/s owing to the fact that

existing TRAU frames are used. The transmission of data for CS-3 and CS-4 would

require larger transport capacities via Abis and would thus involve serious modifica-

tions in the existing network architecture. For this reason, only coding schemes CS-1

and CS-2 are supported in GR2.0/BR5.5. Of these two, CS-1 is particularly important.

Due to the unrestricted redundancy in data transmission, CS-1 is well suited to serve

as a safe basic coding for RLC/MAC data and control blocks. With a high-quality ra-

dio interface CS-1 data transmission rates of up to 8 kbit/s are possible. Even if the

air interface quality (the C/I ratio) decreases, the rate of transmission decreases very

slowly.

Under favorable radio transmission conditions, CS-2 achieves higher transmission

rates, with a maximum at 12 kbit/s. However, the rate of transmission depends more

strongly on the C/I ratio than with CS-1.

This is even truer of coding schemes CS-3 and CS-4, respectively, whose transmis-

sion rates are considerably higher than those of CS-1 and CS-2 under good radio

transmission conditions; but they rapidly decrease if the quality of the radio transmis-

sion interface gets worse.


11


CS 1 - 4: Bit Rate Comparison

18 17 16 15 14 13 12 11 10 9 8 7 6

NetThroughput(kbit/s)

0

2

4

6

8

10

12

14

16

18

20

CS1

CS2

CS3

CS4

5

Channel Coding

• Introduction: CS-1 (9,05 kbit/s & CS-2 (13,4 kbit/s)

• CS-1: basic coding for RLC/MAC data & control blocks

• no CS-3 (15,6 kbit/s), CS-4 (21,4 kbit/s)

→ Abis limitation (current TRAU frames: 16 kbit/s)

Carrier / Interference C/I (dB)

Fig. 7 Comparison of the efficiency of the four coding schemes under realistic circumstances of the air interface

12

1.5 Logical GPRS Radio Channels

Use of "classical" logical channels for GSM-CS

A Logical channel is used for a special purpose/contents. For example the MSs have

to find out if this cell is a suitable one (operated by the "right" network operator),

which features are offered (e.g. HR/FR/EFR, GPRS, ...), what is the structure of Um

(channel combination), ... This is provided by the BCCH which is naturally only

transmitted in the downlink. Some resources have to be given for initial access for the

MS (RACH). For these reasons logical channels have been defined to fulfill all tasks,

which are necessary in a GSM network on the air interface (see figure 13).

The GPRS subscribers will share the air interface with the circuit switched users. On

the other hand the protocol structure of GPRS is different from "classical" GSM-CS.

Therefore the user traffic and (part of) the signaling will have to be separated. Before

this separation can take place the different MS (GPRS/non-GPRS) have to be han-

dled by signaling procedures for access (channel assignment. There are two solution

of this problem. The first one is to use (some of) the logical channels for GSM-CS:

The GPRS-MS detects the BCCH of this particular cell and looks for the system in-

formation to find out if GPRS is available. If this is a cell belonging to the same rout-

ing area the MS can choose this cell and wait for paging or for the user to use the

RACH for activating a PDP. In case that the user wants to run an PS application the

GPRS MS will use an access burst (RACH) which indicates that this is a GPRS MS

and the request will be answered by the PCU assigning resources for packet

switched traffic (time slots reserved for GPRS). Signaling (e.g. for authentication) will

then take place using these resources indicated by the message in the AGCH.

So GPRS uses some of the logical channels of GSM-CS. On one hand this can be

an advantage if the resources are sufficient. On the other hand if in the future more

and more GPRS traffic has to be handled, separate logical channels reserved for

GPRS MS will have to be given. This is the second solution. In any case the GPRS

MS will have to look for the BCCH of the cell to find out if GPRS is available. If the

second solution has been chosen the GPRS MS will also read information where a

PBCCH (Packet Broadcast Control Channel) is to be found (which time slot). This

second solution will be explained in figure 14.


13


Allocation of dedicated signalling channel

Dedicated signaling MS ↔ BTSE (Call

Setup, LUP, Security, SMS, CBCH,...)

Signaling

Traffic

User Data

CGI, FR/EFR/HR, GPRS available

frequency hopping, channel combination,...)

Time synchronisation + BSIC, TDMA-No.

Traffic Channel/H

DL

DL

UL

UL + DL

DL

UL

+

BCCH

FCCH

SCH

PCH

AGCH

RACH

SDCCH

SACCH

FACCH

TCH/F

TCH/H

frequency synchronisation

Paging / Searching (MTC)

Request for access

Measurement Report,

TA, PC, cell parameters,...

Signaling instead of TCH

BCH

CCCH

DCCH

User traffic (Full Rate)

User traffic (Half Rate)

Logical Channel

(for GSM Circuit Switched)

Synchronisation Channel

Frequency Correction Channel

Access Grant Channel

Random Access Channel

Paging Channel

Broadcast Control Channel

Stand Alone Dedicated

Control Channel

Broadcast Channel

Slow Associated

Control Channel

Fast Associated

Control Channel

Traffic Channe/Fl

Dedicated Control Channel

Common Control Channel

NCH

Notification Channel

Notifying MSs

Fig. 8 "Classical" logical channels of GSM may be used by GPRS users too

14

Use of new logical channels for GPRS

In addition to the nine existing logical radio channels used for signaling (BCCH, SCH,

FCCH, PCH, RACH, AGCH as well as SDCCH, SACCH and FACCH) and the Traffic

Channel (TCH) for circuit switched user information, a new set of logical channels

was defined for GPRS.

Packet traffic is realized by means of the Packet Traffic Channel (PTCH), which in-

cludes the following:

Packet Data Traffic Channel PDTCH.

Packet Associated Control Channel PACCH

Packet Timing advance Control Channel PTCCH

The PDTCH is temporarily assigned to the mobile stations MS. Via the PDTCH, user

data (point-to-point or point-to-multipoint) or GPRS mobility management and session

management GMM/SM information is transmitted.

The PACCH was defined for the transmission of signaling (low level signaling) to a

dedicated GPRS-MS. It carries information relating to data confirmation, resource al-

location and exchange of power control information.

New GPRS signaling channels are mainly specified analogously to GSM Phase1/2.

The Packet Common Control Channel PCCCH has been newly defined. It consists

of a set of logical channels, which are used for common control signaling to start the

connection set-up:

Packet Random Access Channel PRACH

Packet Paging Channel PPCH

Packet Access Grant Channel PAGCH

Packet Notification Channel PNCH

PRACH and PAGCH fulfill GPRS-MS functions, which are analogue to the “classical”

logical channels RACH and AGCH for non-GPRS-users. The PNCH is used for the

initiation of point-to-multipoint multicast (PtM multicast).

For the transmission of system information to the GPRS mobile stations, the

Packet Broadcast Control Channel PBCCH

was defined analogue to the “classical” BCCH.

In a physical channel all different types of logical channels can be contained (no

separation into traffic and signaling channels respectively as is done in conventional

GSM). The differentiation of channel contents is carried out per radio block using the

MAC header, i.e. contents are specified for the four normal bursts of a radio block

sent in each case.

The MAC function, which distributes the physical channel to the various mobile sta-

tions and allocates radio resources to an MS can also use the conventional logical

channels in GSM.


15


Logical channels

for GPRS

PBCCH

PRACH

PPCH

PNCH

PAGCH

PACCH

PTCCH/U

PTCCH/D

PDTCH

Packet Broadcast

Control Channel

Packet Random

Access Channel

Packet Paging

Channel

Packet Notification

Channel

Packet Access

Grant Channel

Packet Associated

Control Channel

Packet Timing Advance Control

Channel Uplink/Downlink

Packet Data

Traffic Channel

Packet

Signaling

Packet

Traffic

Broadcast channel

Common

Control

channels

Dedicated channels

Packet System

Information

Access request for

UL packet data

transmission

Paging GPRS-MS

(PtP)

Paging GPRS-MS

(PtM)

Resource allocation

Dedicated signaling

MS-network,

e.g.power control

Timing advance

Determination and

Control

Transmission of

User data

UL

DL

DL

DL

UL&DL

UL&DL

UL

Fig. 9 New logical channels for GPRS

16

1.6 Multiframes in GPRS

The GPRS packet data traffic is arranged in 52-type multiframes (GSM Rec. 03.64).

52 TDMA frames in each case are combined to form one GPRS traffic channel multi-

frame, which is subdivided into 12 blocks with 4 TDMA frames each. One block

(B0-B11) contains one radio block each (4 normal bursts, which are related to each

other by means of convolutional coding). Every thirteenth TDMA frame is idle. In the

idle frame the PTACCH is sent. The idles frames are used by the MS to be able to

determine the various base station identity codes BSIC, to carry out timing advance

updates procedures or interference measurements for the realization of power con-

trol.

For packet common control channels PCCH, conventional 51-type multiframes can

be used for signaling or 52-type multiframes. The GPRS users can use "classical"

common control channels of GSM before they will be directed onto their PTCHs. All

mobiles will read the BCCH anyway. Either in case of GSM mobiles to fulfill the same

tasks as before and for GPRS equipment this logical channel will indicate weather

GPRS service is available and if extra logical channels (PBCCH, PPCH, ...) are used.

GSM CS traffic and GPRS subscribers are clearly separated so that there is no con-

flict due to different signaling or multiframe structure.

It is important that there are no "visible" changes for "GSM only mobiles" due to the

introduction of GPRS. GSM CS connections will use for example the same 26 multi-

frame structure for TCH and the 51 multiframe structure for signaling.


17


iB0 B1 B2 B3 B4 B5 i B6 B7 B8 i B9 B10B11 i

52 TDMA Frames = PDCH Multiframe

4 Frames 1 Frame

New multiframe

for GPRS

• PDCH follows 52 multiframe structure

• 52 Multiframe: 12 Blocks à 4 TDMA-frames

• PCCCHs: „classical“ 51er Multiframes

or 52er Multiframes

B0 - B11 = Radio Blocks (Data / Signaling)

i = Idle frame (PTCCH)

• BCCH indicates PDCH with PBCCH (in B0)

• DL: this PDCH bears PDCCH & PBCCH

PBCCH in B0 (+ max. 3 further blocks; indicated in B0)

PBCCH indicates PCCCH blocks & further PDCHs with PCCCH

• UL: PDCH with PCCCH: all blocks to be used for PRACH, PDTCH, PACCH

PDCH without PCCCH: PDTCH & PACCH only

Idle frame:

• Identification of BSICs

• Timing Advance Update Procedure

• Interference measurements

for Power Control

Fig. 10 Multiframes for GPRS consist of a certain time slot in 52 consequent TDMA frames

18

Chapter 4

Procedures

Procedures Sidemen's

Contents

1 Activation of GPRS Services 23

1.1 GPRS Identities 34

1.2 Mobility Management States 68

1.3 Packet Data Protocol PDP States 192

1.4 GPRS Packet Data Transmission 101 14

1.5 Combined GPRS & IMSI Attach 16

1.6 PDP Context Activation Procedure 18

1.7 Start of Mobile Originated Packet Transfer 20

2 Exercise 23

3 Solution 27

Procedures

1


1 Activation of GPRS Services

Activation of

GPRS services

GPRS:

Procedures

Fig. 1

2

Sidemen's Procedures

1.1 GPRS Identities

1.1.1 Regional Organization of GPRS

A set of identities were introduced in GSM and GPRS to identify a subscriber, as well

as to keep track of him. Following identities are well known in GSM:

LAI: (Location Area Identity) covers a set of cells, where a subscriber was "seen"

last.

CGI: (Cell Global Identity) the unique number of a cell of a PLMN, composed the LAI

and the CI (cell identity).

Next to the existing GSM identities there is also a new GPRS specific identity, the

RAI (Routing Area Identity). This identity, defined by an operator, comprises one or

several cells. It is broadcasted by the (P)BCCH. If a GPRS mobile leaves a routing

area, a Routing Area Update Procedure has to be taken place. The RAI is used in the

same way as the LAI. The Routing Area is more precise than the location area. A

Routing Area is a subset of one and only one Location Area.

RAI: LAI + RAC (Routing Area Code) = MCC + MNC + LAC + RAC

Regional Organisation of GPRS

Location Area

Routing area

cell

LACMNCMCC

RACLACMNCMCC

CILACMNCMCC

Fig. 2 Regional organization of GPRS

3

Procedures Sidemen'


1.1.2 Subscriber Identities and Subscriber Services

IMSI (International Mobile Subscriber Identity):

This is an unique number allocated to each subscriber in GSM. This was adapted

also for GRPS-only mobile subscribers.

PTMSI (Packet Temporary Mobile Subscriber Identity):

This identity is allocated to each GPRS attached mobile. Its task is similar to the

TMSI. The discrimination between the TMSI and P-TMSI is realized by allocation to

the two most significant bits to 11 for GPRS and to 00, 01, 10 for GSM.

PDP Address:

On the network layer, the subscriber may identified by one or more network layer ad-

dresses, so-called PDP Addresses, which are allocated to the subscriber temporally

or permanently.

One central question in GPRS is: how can a logical link between a mobile and a

SGSN be identified uniquely? This is done with the NSAPI/TLLI pair, which are

unique within a routing area.

NSAPI (Network layer Service Access Point Identifier):

The NSAPI is used as a service access point between the higher level and the

SNDCP. The NSAPI is used to identify the corresponding PDP context, which is as-

sociated with the GPRS MS PDP address on the side of the GSN.

TLLI (Temporary Logical Link Identity):

The TTLI is used to define a one to one correspondence within a Routing Area be-

tween the MS and the SGSN. This is only known by the MS and the SGSN.

TID (Tunnel Identifier):

This identity is used by the GTP to identify a PDP context. The TID is a combination

of the IMSI and the NSAPI. The IMSI/NSAPI pair uniquely identifies a PDP context.

GSN-Address:

The GSN Address is the IP-no. of GSN for the GPRS IP backbone.

The GSN-number is the ISDN-no. for a GSN

Access Point Name:

This name indicates in the NSS backbone, which GGSN shall be used. Furthermore

it can indicate the external network, the subscriber wants to be attached to, for in-

stance the "Internet Service Provider" Name.

4

Procedures Sidemen'


Subscribers Identities

S

G

S

NG

G

S

N

G

G

S

N

TLLI IMSI

Who is the owner of one packet

Which application does the packet belong to

S

G

S

N

G

G

S

N

NSAPI

1 2

3 4

Fig. 3 Subscribers identities in the network

5


1.2 Mobility Management States

States of the GPRS services

With regard to point-to-point PtP packet data transmission the GPRS service oper-

ates in two independent state models/circles. One circle describes the mobility man-

agement behavior whereas the other is assigned to the activation of a packet data

protocol PDP.

The circle related to mobility management states in the MS and the associated SGSN

consist of the:

"Idle" state

"Standby" state

"Ready" state

The circle related to a specific packet data protocol has the:

"Inactive" state

"Active" state

Packet Data

Protocol

PDP

States of

GPRS services

2 circles

regarding:

Inactive

State

Active

State

Idle

State

Ready

State

Standby

State

Mobility

Management

Fig. 4 States of GPRS services with regard to mobility management and packet data protocols

6

Procedures Sidemen'


"Idle" state

A mobile station MS in the idle state is detached from the GPRS. Only GPRS sub-

scription data is available in the HLR. No further information exists in other network

units such as SGSN and GGSN. It is not possible to activate a packet data protocol

PDP or to maintain a PDP in its active state. The GPRS MS must monitor the BCCH

to determine the availability of cells, which support GPRS services. Accordingly, the

GPRS MS can carry out PLMN and cell selection procedures. To exit idle state, the

MS must execute the “attach” procedure. Upon successful completion of this proce-

dure, the MS changes to ready state.

"Standby" state

In the standby state the GPRS MS is attached to the GPRS network. The GPRS and

the SGSN have a mobility management context comparable to the circuit switched

connections. The MS monitors the broadcast channel to determine the availability of

cells offering GPRS services and also the paging channel PCH, to be informed about

paging requests. The SGSN recognizes/stores the routing area RA of the GPRS-MS.

The routing area is a sub-unit of the location area LA, in other words a more detailed

determination of the GPRS-MS location. The GPRS-MS informs the SGSN about

changes of the routing area and answers paging requests.

"Ready" state

In the ready state, the SGSN detects the current cell of the GPRS-MS beyond the

routing area RA of the GPRS-MS. If the GPRS-MS changes cells, it informs the

SGSN. Paging is thus superfluous in the ready state. The DL packet data transfer

can be performed any time. Ready state does not mean that a physical connection is

established between SGSN and MS. Only in the ready state, SGSN and MS can

transfer data packets. MS and SGSN exit ready state upon expiry of a ready timer or

in case of a faulty packet data transmission and change to standby state. Upon log-

off, i.e. execution of a detach procedure; MS and SGSN exit ready state and change

to idle state.

7

Procedures Sidemen'


Mobility Management

States

IDLE

state

READY

state

STANDBY

state

GPRS

detach

expiry of mobile

reachable timer

expire READY Timer /

Transmission errors

GPRS

attach

SGSN: Paging /

MS: initiates Transfer

• SGSN & GGSN without

MS information

• only HLR contains subscription data

• no PDP context can be activated

• MS observes BCCH

• PLMN- & Cell Selection

• SGSN knows Routing Area & cell!!

• UL & DL packet transmission possible

• SGSN ↔ MS: MM-Context

• SGSN knows Routing Area

• MS observes BCCH, PCH

• initiates RA-Update

• reacts to Paging Request

• MS initiates Cell Update

Fig. 5 Mobility management states

8


1.3 Packet Data Protocol PDP States

There are separate state circles for every authorized PDP of a GPRS-MS

"Inactive" State

The inactive state of a PDP means that this PDP is not operating at that moment.

There is no routing context in the MS, SGSN and GGSN. A transition in the active

state is only possible if there is a mobility management connection and if MS and

SGSN are in the standby or ready state.

No data transfer is possible in the inactive state. Data packets, which reach the

GPRS network are either rejected or ignored.

"Active" State

In the active state the MS, GGSN and SGSN are in a routing context. Data can be

transmitted or received by the MS. The active state is ended explicitly if the MS deac-

tivates a certain PDP. With GPRS detach and expiry of the standby timer, all the acti-

vated PDP are deactivated, too.

PDP States

INACTIVE

state

ACTIVE

state

De-activation PDP context /

GPRS detach

expiry STANDBY timer

Activation

PDP context

• PDP not activated

• no Routing-context

for MS, SGSN & GGSN

• no data transmission possible !

Transition to „Active“ State

only if MM-context exists

( MS & SGSN: STANDBY / READY)

• Routing context

for MS, SGSN & GGSN

• Data transmission possible !

Fig. 6 States of a packet data protocol

9

Procedures Sidemen'


1.4 GPRS Packet Data Transmission

The transmission of GPRS packet data presupposes the execution of

� GPRS Attach Procedure as well as of the

� PDP Context Activation Procedure.

In the case of a mobile packet data transfer, a one or two-phase packet access is

added. This access procedure is necessary for packet data transfer.

Common Mobility Management / MS-Location

To reduce the signaling load via the radio interface during GPRS and non-GPRS op-

eration, important mobility management MM procedures are carried out jointly (com-

mon MM). This regards the procedures for: attachment / detachment, location & rout-

ing area update and paging.

The result of a GPRS routing area update procedure is stored in the SGSN. The rout-

ing area represents a more exact indication of the MS location, than is actually

needed for non-GPRS services. Triggered by the MS (in the framework of a RA up-

date) the SGSN informs the MSC/VLR via the Gs interface of a change in the loca-

tion areas, which has taken place simultaneously.

Further mobility management procedures are also executed via GPRS procedures. If

possible, all messages containing mobility management information are transferred

through signaling data packets. The MM procedures are defined in the GGM/SM

(GPRS Mobility Management & Session Management).

10

Procedures Sidemen'

Abbreviations

Abbreviations Siemen

Contents

1 Abbreviations 23

Abbreviations

1


1 Abbreviations

AAL ATM Adaptation Layer

AAL5 AAL Type 5

ABC Administration and Billing Center

ACCG ASN Controller and Clock Generator

ACIS ATM Communication Interface Simulator

ACT Active

ADET Application Database Engineering Team

AGCH Access Grant Channel

ALI Alarm and Interface Module

ALIB Alarm and Interface Module Type B

ALM ATM Layer Module

AMP ATM Bridge Processor

AMX ATM Multiplexer

AMXE AMX Module type E

AP Accounting Probe

APE Abgesetzte Peripherie Einheit (Remote Peripheral Unit)

API Application Programming Interface

APS Application Program System

ASIC Application Specification Integrated Circuit


ASN.1 Abstract Syntax Notation 1

ASNF ASN Module Type F

ASNG ASN Module Type G

ASNH ASN Module Type H

ATM Asynchronous Transfer Mode

ATM230 ATM Interface Asic with 200- and 30-Mbit Interfaces

AUB Access Unit Broadband

BAP Base Processor

BCH Broadcast Channel

BCCH Broadcast Control Channel

2

Siemens Abbreviations

BCT Basic Craft Terminal

BG Border Gateway

BigFUT a FUT (functional unit test) including all functional units

BIST Built In Self Test

BOP Basic Operation

BOST Board Self Test

BSC Base Station Controller

BSS Base Station System

BSSGP Base Station System GPRS Protocol

BVC Base Station Virtual Connection

C-ID Charging Identifier

CAP Coordination Processor

CBR Constant Bitrate

CCCH Common Control Channel

CCS7 Common Channel Signaling System No. 7

CCS7E Common Channel Signaling System No. 7 Enhanced

CDB Database for C-based Peripherals

CDC Central Data Collector

CGI Cell Global Identity

CGU Clock Generator Unit

CHILL CCITT High Level Language

CI Cell Identifier

CMISE Common Management Information Service Element

CP113 Co-ordination Processor 113

CT Context Table

CTI Context Table Index

CU(-C) Control Unit (shelf type C)

DBLU DBMS less Unit

DBMS Database Management System

DCCH Dedicated Control Channel

DLCI Data Link Connection Identifier

DNS Domain Name Server

DRAM Dynamic RAM

3



DS1 Digital Signal, level 1

DSDL DBMS Specific Definition Language

E1 European PDH Signal, Level 1

ECC Echo Cancellation Circuit

EFD Event Forwarding Discriminator

EIR Equipment Identity Register

EPC External Processor Communication

EPROM Erasable Programmable Read Only Memory

ESGEN Extended MML Syntax Generator

ETSI European Telecommunications Standard Institute

EWSD Siemens Digital Electronic Switching System

EWSD V13 Elektronisches Wählsystem Digital Version 13

EWSX EWSXpress

FACCH Fast Associated Control Channel

FAT Functional Area Test

FCCH Frequency Correction Channel

FEPROM Flash EPROM

FFS For Further Study

FP Frame Relay Processor

FPSM Frame Relay Processor Shared Memory

FR Frame Relay

FR-LIC Frame Relay Line Interface Card

FT1 Functional Test 1 (offline-test)

FT2 Functional Test 2 (online-test)

FT3 FT2 including the HLR

FTP File Transfer Protocol

FUT Functional Unit Test

FW Firmware

GDB GPRS Database

GDMO Guidelines for definition of Managed Objects

GGSN Gateway GPRS Support Node

GMM GPRS Mobility Management

GMM_AF GMM Application Function

4


GMM_TF GMM Transport Function

GOAM GPRS Operation and Maintenance Applications

GPRS General Packet Radio System

GR GPRS Release

GR1.0 GPRS Release 1.0

GSN GPRS Support Node

GTP GPRS Tunnel Protocol

GUI Graphical User Interface

HLR Home Location Register

HPDB High Performance Database

HW Hardware

HWT Hardware Tracer

I/O Input / Output

ICA IDS Communication via ATM

ICMP Internet Control Message Protocol

IDS Interactive Debugging System

IMEI International Mobile Equipment Identity

IMSI International Mobile Subscriber Identity

INT_CID Internal Change ID

INT_CID Internal Charging Identifier

IOC Input Output Controller

IOT Interoperability-Test

IOT Interoperability-Test

IP Internet Protocol

IPC Internal Processor Communication

IPv4 IP version 4

ISP Internet Service Provider

ITP Internal Transfer Protocol

ITU International Telecommunication Union

IWE Interworking Entity

L&S Load and Stress Test

L&S Load and Stress Test

LA Location Area

5



LAN Local Area Network

LCF Log Control Function

LCT Local Craft Terminal

LDC Local Data Collector

LED Light Emitting Diode

LIC Line Interface Card

LLC Logical Link Control

LLE Logical Link Entity

LM Layer Management

LPS LIC Protection Switch

MAP Mobile Application Part

MBC Message Based Communication

MBS Maximum Burst Size

MCI Maintenance Craft Interface

MDB Maintenance Database

MDD Magnetic Disk Device

MIPS Million Instructions Per Second

MM Mobility Management

MMU Memory Management Unit

MOD Magneto Optical Disk

MP Main Processor

MP-AP Main Processor used for application SW processing

MP-SA Main Processor with Standalone Capabilities

MP:ACC Main Processor for Accounting Management

MP:LM Main Processor for Layer Management

MP:OAM Main Processor for Operation and Maintenance

MP:PD Main Processor for Packet Dispatching

MPC Main Processor (Version C)

MPU Main Processor Unit

MPUB Main Processor Unit B

MPUC Main Processor Unit C

MS Mobile Subscriber

MSC Mobile Services Switching Center

6


MSU Message Signaling Unit

MTP Message Transfer Part

N-PDU Network PDU

NC Node Commander

NNI Node Network Interface

NS Network Service

NS-VC Network Service Virtual Connection

NS-VL Network Service Virtual Link

NSAPI Network SAPI

NSS Network Subsystem

O&M Operation and Maintenance

OA&M Operation, Administration and Maintenance

OMC Operation and Maintenance Center

OMC-B OMC for the BSS

OMC-S OMC for the SSS

OS Operations System

P-TMSI Packet Temporary Mobile Subscriber Identity

PCB Printed Circuit Board

PCH Paging Channel

PCM Pulse Code Modulation

PCP Peripheral Control Platform

PCR Peak Cell Rate

PCU Packet Control Unit

PD Packet Dispatcher

PDET Project Database Engineering Team

PDN Packet Data Network

PDP Packet Data Protocol

PDU Packet Data Unit

PLL Phase Locked Loop

PLMN Public Lands Mobile Network

PM Performance management

PRH Protocol Handler

PRH:MGR Protocol Handler Manager

7



PRM Packet Routing Management

PRM-S Packet Routing Manager SGSN

PRT Packet Routing and Transfer Function

PSAX Power Supply 5V for Fibre Optic Transceiver type X

PSU Power Supply Unit

PVC Permanent Virtual Connection

Q3 Q interface at the GSN nodes

QoS Quality of Service

RA Routing Area

RAC Routing Area Code

RACH Random Access Channel

RAI Routing Area Identity

RAM Random Access Memory

RB Record Builder

RF Record Formatter

RPC Remote Procedure Call

RSS Radio Subsystem

SA Stand Alone

SAAL Signaling AAL

SACCH Slow Associated Control Channel

SAPI Service Access Point Identifier

SAR Service Access Routines

SCB Sequencer Control Block

SCB SSNC Control Shelf Basic

SCCP Signaling Connection Control Part

SCE SCB-extended

SCE SSNC Control Shelf Extended

SCH Synchronization Channel

SCR Sustainable Cell Bitrate

SDL System Description Language

SDR Symptom Data Recording

SDRAM Synchronous DRAM

SDRT Symptom Data Transport

8


SGSN Serving GPRS Support Node

SICAT SDL Integrated Computer Aided Tool set

SLR SGSN Location Register

SM Session Management (GPRS)

SM Signaling Manager (part of #7 application)

SMP Standard Maintenance Protocol

SMU Statistical Multiplexing Unit

SNDCP Subnetwork Dependent Convergence Protocol

SP Synchronization Point

SPOTS Support for Planning, Operation & Maintenance and Traffic analysis

SPU Service Provision Unit

SQS Siemens Q3 Specification

SS7 Signaling System #7

SSNC Signaling System Network Control

SST Sub System Test

STATS Statistics Support

STB Standby

STM-1 Synchronous Transport Module Level 1

SVE System Verification Environment (a tool for proving the formal correctness of a design)

SW Software

SWERR Software Error Report

TCH Traffic Channel

TCP Transmission Control Protocol

TID Tunnel Identifier

TLLI Temporary Logical Link Identifier

TLM Trunk Line Management

TM Traffic Measurements

TMN Telecommunications Management Network

TODE Total Outage Detection

TPL Throughput Limiter

TSC Through Switched Connection

TTY Teletype

9



UDP User Datagram Protocol

UNI User Network Interface

VBR Variable Bitrate

VC Virtual Connection

VCPU Virtual Central Processing Unit

VGA Video Graphics Adapter

vGGSN virtual GGSN

VLR Visited Location Register

VOCOC Vision O.N.E. Chill Operating System

VP Virtual Path


WWW World Wide Web

xGSN SGSN or GGSN

10



Sub-sections

UMTS Introduction

The Third Generation (3G) 1

UMTS Evolution 2

The UMTS Network 3

Security Features 4

UTRA Aspects 5

UMTS Radio Access: Basic Principles 6

Appindex 7

UMTS Introduction


Sub-section identification Pages1 The Third Generation (3G) 1 - 32 2 UMTS Evolution 1 - 10 3 The UMTS Network 1 - 39 4 Security Features 1 - 36 5 UTRA Aspects 1 - 19 6 UMTS Radio Access: Basic Principles 1 - 41 7 Appendix 1 - 17


Chapter 1


The Third Generation (3G) Siemens

Contents

1 IMT-2000 23

1.1 3G / IMT-2000 Standardization 34

1.2 3G Frequency Ranges 1214

2 UMTS 1721

2.1 The UMTS Standard 1822

2.2 3G / UMTS: 4 Zone Concept / Data Rates 2732

2.3 UMTS Licenses 3136

3 Exercise 3339

4 Solution 3847


1


1 IMT-2000

The 3rd Generation (3G)

IMT-2000International Mobile Telecommunications

Future Public Land Mobile

Telecommunication Systems

Global Mobile

Personal

Communication

by Satellite

International Mobile

Telecommunications

Standardization:

International Telecommunication

Union

Time & Frequency

Fig. 1

2

Siemens The Third Generation (3G)

1.1 3G / IMT-2000 Standardization

The third generation of mobile communication systems (3G) has been in discussion since the beginning of the 1990's under the term FPLMTS (Future Public Land Mobile Telecommunication Systems). This was taken to refer to the terrestrial branch of mobile communications. In the mid-1990's, the term was changed to IMT-2000. IMT-2000 stands for International Mobile Telecommunications. 2000 indicates not only the time frame for introduction of the systems, but also the frequency band used (in MHz). In addition to terrestrial systems, IMT-2000 also includes mobile satellite systems. These were discussed under the term GMPCS for Global Mobile Personal Communication by Satellite.

The International Telecommunication Union (ITU) is responsible for the IMT-2000 specification. The ITU derives from the International Telegraph Union founded in Paris in 1865. In 1848 the ITU was included as a special organization in the United Nations UN. The ITU is responsible for international coordination in the area of telecommunications. E.g. for the allocation of frequency spectrum, coordination of the development of telecommunication systems, promotion of bilateral agreement on low charges, implementation of studies, issue of regulations and recommendations and much more. The ITU is also in charge of the global 3G coordination, i.e. for IMT-2000 guidelines and frequency recommendations.

1G and 2G systems are characterized by a variety of different standards for various applications. Each of the standards has specific technical attributes, advantages and disadvantages, applications, ranges and costs, and has been optimized for different subscriber groups. Many of these systems exist(ed) solely at regional or national level and are incompatible with each other.

Different to 1G and 2G, 3G has been planed as a family of compatible standards, allowing world-wide access, being used for diverse applications.

The IMT-2000 concept devised by the ITU includes the following major aspects:

��Global, seamless access to mobile communications systems

��Compatibility between all members of the IMT-2000 family

��Downward-compatibility with the major 2G systems (e.g., GSM, IS-95)

��Convergence between mobile and fixed networks

��High data rates for mobile communications

��Circuit- and packet-switched (CS & PS) transfer of data

��Facilitation of multimedia applications

��Inexpensive, flexible telecommunications access also for developing countries

3

The Third Generation (3G) Siemen


e.g. UMTS, cdma2000, UWC-136

2G(digital)

Paging Systemse.g. ERMES

Cordless Telephonee.g. DECT, PACS, PHS

WirelessLocal Loops

WLL

PMR

e.g. TETRA

Cellular systemse.g. GSM, D-AMPS,

IS-95, PDC

MSSe.g. IRIDIUM, ICO,

Globalstar

1G(analog)

Cordless Telephonee.g. CT1, 1+

Paging Systems,e.g. City Call

wirelessTelephone cell

Private Mobile Radio

PMR

Cellular systemse.g. C450, NMT, AMPS

MSSe.g. INMARSAT

3G

1 family of standards

for all

• applications

• countries

different, incompatible standards for

different applications, countries & regions

IMT-2000

� worldwide, seamless access

�� terrestrial & MSS component� Compatibility: IMT-2000 family� downwards-compatible with 2G

� Fixed Mobile Convergence FMC� high data rates� Multi Media applications� CS & PS� low price & flexible access for

developing countries!

Fig. 2

4

IMT-2000 RTT Standardization

IMT-2000 is pledged to enabling global mobile communications. In this respect, the ITU drew up guidelines for IMT-2000 systems and requested the regional standardization organizations (Standards Development Organizations – SDO's) to submit proposals based on the guidelines. These are to be examined in conjunction with the ITU and adapted correspondingly in order to assure compatibility between the individual members of the IMT-2000 family.

Many regional and national SDO's throughout the world participated in the drafting of proposals. They include the following:

��for Europe, the ETSI (European Telecommunication Standardization Institute)

��for Japan, the TTC (Telecommunication Technology Committee) and the ARIB (Association of Radio Industries and Business), an organization for proposing and promoting radio-based development

��for South Korea, the TTA (Telecommunication Technology Association)

��for the USA, the T1 (Standards Committee T1 Telecommunications) and TIA (Telecommunication Industry Association) which represent the interests of many American companies in the information and telecommunications sector and develop standards for the ANSI (American National Standards Institute)

��for China, the CATT (China Academy of Telecommunication Technology)

��and a number of international companies that develop mobile satellites (Inmarsat, ICO, ESA, Iridium,..)

5



IMT-2000 Development:regional Standards Development Organisations

ITU: IMT-2000

ESA: European Space Agency

TTA: Telecommunications Technology Association

CATT: China Academy of Telecommunication Technology

ARIB: Association of Radio Industries and Business

TIA: Telecommunication Industry Association

T1: Standards Committe T1 Telecommunications

ETSI: European Telecommunications Standardization Institute

ICO: Intermediate Circular Orbits

Inmarsat: International Maritime Satellite Organisation

ETSI(Europe)

ARIB, TTC(Japan)

TTA(South Korea)

TIA, T1(USA)

CATT(China)

ICO, Inmarsat(MSS)

ESA, Iridium(MSS)

• 1985: Start ITU studies on FPLMTS (IWP8/13)

• 1992: Frequency reservation in WARC`92

• 1990 - 95: TG 8/1 defines FPLMTS requirements

Fig. 3

6


RTT proposals for IMT-2000

Studies on FPLMTS commenced in 1985 with the founding of a work group in the ITU designated as the Interim Working Party IWP8/13. Questions regarding the necessary bandwidths and frequency bands as well as the level of similarities required to ensure compatibility were discussed here. Guidelines for FPLMTS / IMT-2000 were defined in the 1990's by the ITU task group TG8/1.

Further development stages were as follows:

��Drafting of proposals for IMT-2000 systems (3Q1996 – end of 1997)

��Evaluation of the proposals (2Q1997 – 3Q1998)

��Consensus on Intellectual Property Rights IPR and compatibility (2Q1997 – 1Q1999)

��Finalized specification of the individual standards for the IMT-2000 family (1999)

Another significant date was June 30, 1998 – the deadline for submission of Radio Transmission Technology (RTT) proposals to the ITU. Different regional standards development organizations SDO’s were involved in the development of IMT-2000 systems. 15 proposals for implementing IMT-2000 radio transmission technologies (RTT) were submitted to the ITU by the end of June `98 (deadline). Two further proposals followed a few months later, but were still accepted.

The total of 17 proposals were devised and submitted by the world’s most important SDO’s – i.e., from ETSI (Europe), ARIB (Japan), TIA (USA), T1 (USA), TTA (South Korea) and CATT (China), as well as by the MSS operators ICO, Inmarsat, ESA and Iridium. 11 proposals submitted by the various SDO’s refer to terrestrial, cellular systems. The other 6 proposals from the MSS operators concern satellite systems that are intended to provide genuine global coverage for the 3G systems.

7



RTT proposals

for IMT 2000

T1: NA: W-CDMA

TIA: UWC-136

WIMS W-CDMA

cdma2000

Europe

ICO: ICO RTT

ETSI: UTRA

DECT

Inmarsat: Horizons

ESA: SW-CDMA

SW-CTDMA

South Korea

TTA: CDMA II

CDMA I

SAT-CDMA

JapanARIB: W-CDMA

ChinaCATT: TD-SCDMA

USA

Iridium: INX

MSS

RTT: Radio Transmission Technology

ITU-Deadline

für RTT Proposals:30.06.98

Source: ITU

T1, TIA: WP-CDMA

Fig. 4

8


RTT Proposals

11 of the total number of 17 RTT proposals referred to terrestrial, cellular systems. They cover all commercially viable areas of the mainland including coastal areas – in other words, from indoor areas (i.e., quasi stationary or lowest speed, smallest range) to pedestrian (i.e., low speed, small and medium ranges) to vehicular (i.e., wide ranging at medium and high speeds).

Another 6 proposals from the area of mobile satellite systems (MSS) for covering the remaining surface of the globe (sea, deserts, mountains, and sparsely populated, inaccessible regions) were also submitted.

The greatest share of the RTT proposals, particularly for the terrestrial solutions, have so-called CDMA (Code Division Multiple Access) solutions. Different variations of this special multiple access method provide very efficient use of resources via the radio interface and allow flexible, high data rates.

Other methods use “conventional” TDMA (Time Division Multiple Access) methods with different optimization solutions to provide access to 3G systems at the high data rates demanded by the ITU.

SourceDescriptionProposal IndoorPedes-

trian

Vehi-

cularSatellite

DECTDigital Enhanced Cordless

Telecommunicationsx x - - ETSI

Universal Wireless CommunicationsUWC-136 x x x - USA TIA

WIMS W-CDMA

Wireless Multimedia and MessagingServices Wideband CDMA

x x x - USA TIA

Time-Division Synchronous CDMATD-SCDMA x x x - China CATT

Wideband CDMAW-CDMA x x x - Japan ARIB

Asynchronous DS-CDMACDMA II x x x - South Korea TTA

UTRAUMTS Terrestrial Radio Access:

W-CDMAx x x - ETSI

North American: W-CDMANA: W-CDMA x x x - USA T1P1

W-CDMA (IS-95+)cdma2000 x x x - USA TIA

Multiband synchronous DS-CDMACDMA I x x x - South Korea TTA

49 LEO sats in 7 planes at 2000 kmSAT-CDMA - - - x South Korea TTA

Satellite wideband CDMASW-CDMA - - - x ESA

Satellite wideband hybrid CDMA/TDMASW-CTDMA - - - x ESA

10 MEO sats in 2 planes at 10390 kmICO RTT - - - x ICO

Horizons satellite systemHorizons - - - x Inmarsat

Wideband Packet-CDMAWP-CDMA x x x - T1 & TIA

Iridium Next GenerationINX - - - x Iridium

RTT

Proposals

Source: ITU

Fig. 5

9



Harmonization of the RTT‘s

Due to the demand for global compatibility of the IMT-2000 systems and as a result of the improved chances of the individual proposals, many of the RTT solutions proposed were harmonized. The harmonization reduced – in particular for the terrestrial, cellular systems – the number of RTT’s during the period from the middle of 1998 until the end of 1999. The ARIB (W-CDMA) and ETSI (UTRA) proposals were harmonized and further jointly developed as UTRA FDD and TDD components (as a GSM successor system). The IS-95 successor system, CDMA2000, and the UTRA FDD/TDD components were also harmonized. This new IMT-2000 RTT component referred to now as MC-CDMA (instead of CDMA2000) is for the most part harmonized with the UTRA TDD and FDD (now also known as DS-CDMA) components with the result that roaming is possible in theory between the system components. The Chinese TD-SCDMA proposal has also been retained as an IMT-2000 component.

At the same time, UWC-136 remains as a step toward optimization of D-AMPS in the direction of high data rates. UWC-136 is equivalent to EDGE for GSM). Therefore, EDGE has been renamed to Enhanced Data Rates for the Global Evolution, consisting of an "EDGE Classic" component (for GSM enhancement) and an "EDGE Compact" component (for D-AMPS enhancement).

So in general four 3G standards are expected to be more or less important on 3G market: UMTS (FDD mode and TDD mode), MC-CDMA, EDGE and TD-SCDMA.

Now, having finished 3G standardization (ITU TG8/1 closed in 12/99), further plans are made to enhance 3G (denominated as 3.5G) and first studies are planed for 4G development (e.g. in the ITU Working Party WP8F).

10



IMT-2000

RTT Harmonization

CDMA II, W-CDMA

NA: W-CDMA

UTRA, WIMS

CDMA2000

CDMA I TD-SCDMAUWC-136

DECT

Source: ITU

June `98

CDMA FDD

UTRA (FDD)

WP-CDMA

CDMA2000

TDMA/CDMA(Hybrid TDD)

TD-CDMA(UTRA TDD)

TD-SCDMA

TDMA

UWC-136

DECT

Paired:

EDGE

UTRA FDD

MC-CDMA(former

CDMA2000)

Unpaired:

UTRA TDD

TD-SCDMA

March `99

December `99

FDD: Frequency Division Duplex

TDD: Time Division Duplex

DS-CDMA: Direct Sequence CDMA

MC-CDMA: Multicarrier CDMA

TD-SCDMA: Time-Division Synchronous CDMA

12/99 ITU:

TG 8/1 closed &

WP 8F founded: 3.5G / 4G studies

Fig. 6

11


1.2 3G Frequency Ranges

A significant disadvantage of mobile communications is the limited availability of frequency resources. The radio interface can be likened to the eye of a needle for information transfers. The radio interface in most industrial nations has hardly any unused gaps in the range from KHz to GHz. A variety of diverse applications (e.g., radio, TV, radar, mobile communications, radio relay systems, microwave applications, etc.) for industrial, military and private use are competing for the available frequency bands. Licenses are granted at national level.

1G mobile communications systems in Europe were mostly positioned in the 450 MHz and 900 MHz frequency bands. 1G and 2G successor systems in America and Japan occupy the 800 MHz range. Expansions in Japan were implemented for the 1500 MHz range and in America for the 1900 MHz range. For GSM, frequency bands around 900 MHz were reserved for GSM900 and GSM-R, and frequencies around 1800 MHz for GSM1800 in most European countries and in many non-European countries (outside America). The 1800 MHz band is available for different 2G systems (including GSM1900) in different American states.

The European 2G cordless standard DECT is used globally in many countries in the range 1880 – 1900 MHz. The Japanese PHS equivalent used in the South Asian area uses the range 1895 – 1918 MHz.

Frequencies in the range of 1600 MHz are also available to 2G MSS's. Other MSS bands are located between 2.5 and 30 GHz.

A recommendation for the national authorities for reserving frequencies for 3G applications was passed on the initiation of the ITU-R at the World Administrative Radio Conference in February 1992 (WARC-92). The frequency ranges from 1885 –2025 MHz and from 2110 – 2200 MHz are to be reserved globally for 3G systems. They include frequency ranges for MSS's: 1980 - 2010 MHz and 2170 - 2200 MHz.

12



1G & 2G systems

1G (NMT, C450,..)possibly 2G: GSM450

GSM900+ GSM-R GSM1800

DECT

0 250 500 750 1000 1250 1500 1750 2000 frequency [MHz]

MSS

Europe,

Africa,

Australia

1G + 2G: PDC PHSMSS

Japan

2G:PDC

1G: AMPS,2G: D-AMPS, IS-95

2G: GSM1900, IS-95, D-AMPS

MSS

America

1 8 5 0 1 9 0 0 1 9 5 0 2 0 0 0 2 0 5 0 2 1 0 0 2 1 5 0 2 2 0 0 2 2 5 0


1885

2010

2110

1980

2025

2170

2200


WARC-92: 3G Plans

WARC: World Administrative Radio Conference

Frequency reservation

Remaining frequencies < 2 GHz:Military, Industry, Broadcast, TV, Research,

private (households, amateurs),...

Fig. 7

13


Regional 3G reservation

Europe, Japan and South Korea complied for the most part with the recommendations of the WARC-92 regarding reservation of frequency ranges for 3G systems.

Europe: It was defined at European level after a decision taken by the ERC (European Radiocommunications Committee) at the end of 1997 that the corresponding (WARC-92) frequency range, with the exception of the frequency range from 1880 – 1900 MHz (DECT range), is to be made available to 3G systems. Many non-European countries also adopted this frequency reservation.

Japan: With the exception of the frequency range below 1918.1 MHz, which will continue to be used for PHS systems, the entire WARC-92 frequency band was reserved for 3G systems.

South Korea: The full WARC-92 frequency band was reserved for 3G systems.

North America: In 1995 the frequency range between 1850 MHz and 1990 MHz was auctioned in the USA for use by 2G systems (e.g., IS-95, D-AMPS, GSM1900). As a result, the introduction of 3G systems in the USA is experiencing great difficulty. The same applies to Canada. However, smaller ranges (C, E blocks) were reserved here for future applications.

USA,

Canada(C,E reserved)

1850 1900 1950 2000 2050 2100 2150 2200 2250

1850 1900 1950 2000 2050 2100 2150 2200 2250

WARC-92

Europe

Japan;

S. Korea like WARC-92

1885 MHz 2025 MHz

MSSIMT 2000

MSSUMTSGSM 1800DECT

1880 MHz 1980 MHz

MSS

MSSIMT 2000PHS

PCS1900

A C B BC C CEF A FE

2010 MHz

MSSIMT 2000

MSSUMTS

MSSreserved

MSSIMT 2000

2160 MHz

2110 MHz

1895 MHz

1918 MHz2170 MHz

2170 MHz

1990 MHz1910 1930

Regional 3G Reservation

Source: UMTS Forum Report #5

Fig. 8

14



World Radiocommunication Conference WRC 2000

The WRC 2000 in Istanbul, Turkey, was looking for additional 160 MHz spectrum on top of the today available 2G and 3G frequency ranges. Furthermore, a central aspect of the WRC’2000 has been to provide a global harmonization of frequency ranges for 3G. The ability to roam world-wide on 3G frequency ranges is very beneficial for a real 3G mass market. A third aspect has been the extension of 3G frequency ranges to lower frequencies for the deployment of 3G services in rural areas, i.e. in larger cells.

One key principle, which helped in the process of identification of 3G spectrum in WRC’2000 was that the identified 3G spectrum would not preclude the use of these bands by any other services to which they are allocated. Regulators will be reminded at regular intervals that when licensing services in those bands sufficient resources must be provided for 3G services.

The additional bands identified for 3G terrestrial components are:

��806 – 960 MHz

��1710 – 1885 MHz

��2500 – 2690 MHz

The bands, which had been identified for 3G in WARC’92 remain unchanged:

��1885 – 2025 MHz

��2110 – 2200 MHz

The frequency ranges below 1GHz are especially useful for rural services and developing countries. Some countries are planning to use the following frequency range additionally for 3G implementation: 698 – 806 MHz.

The focus of the 3G extension is the frequency range between 2500 – 2690 MHz.

Reference is also made to the 2300 – 2400 MHz frequency range, which is the preferred choice of China.

15



WRC-200005/2000 in Istambul

� additional 3G frequency ranges

� to be used from 2005

� world-wide Harmonisation

� of 3G frequency ranges


cellular

806 960

Harmonisation / Extension:

Refarming 2G frequencies(important for rural service areas)

only somecountries

cellular

1710 1885

Harmonisation / Extension:

Refarming 2G frequencies

cellular

2500 2690


1885

2010

2110

1980

2025

2170

2200

WARC’92

Extension band

China only: 2300 - 2400 MHz

698

Fig. 9

16


2 UMTS

Telecommunication System

UMTS

Standardisation & Concept

World-wide,

seamless

Multimedia access

Universal Mobile

The 3rd Generation (3G)

Fig. 10

17


2.1 The UMTS Standard

The European telecommunications standards institute ETSI began with the development of a successor standard to GSM in the mid-1990's. This standard, referred to as UMTS (Universal Mobile Telecommunication System), is intended to be a European 3G system that meets all IMT-2000 requirements stipulated by the ITU.

ETSI SMG's (Special Mobile Groups) were charged with drafting the UMTS standard. The SMG's also devised GSM and are responsible for its updating.

Different studies on the implementation of the UMTS radio interface, UTRA (UMTS Terrestrial Radio Access), were completed in 1996 and 1997. These studies are regarded as the 1st phase of the UTRA conception.

A total of five concepts were selected in mid-1997 for the implementation of UTRA. These five concepts were named after the first five letters in the Greek alphabet: alpha, beta, gamma, delta and epsilon. The various concepts were evaluated from the middle of 1997 until the end of that year. The evaluation is referred to as the 2nd phase in the UTRA conception. That phase was completed in 01/1998 with the selection of the alpha and delta concepts for UTRA.

In the 3rd phase of the UTRA conception, these two UTRA concepts were harmonized with each other. The harmonization was concluded in 06/1998. Since then the two concepts are known as UTRA FDD and UTRA TDD. At the same time, UTRA was submitted to the ITU as the ETSI proposal for IMT-2000. The ITU accepted UTRA as an IMT-2000 system at the start of 1999.

The Japanese standards association, ARIB, with observer status in the ETSI, also participated in the evaluation and harmonization of UTRA.

As a result, the submissions made by ETSI (UTRA) and ARIB (WCDMA) to the ITU closely match each other in many respects. In view of this similarity, ETSI and ARIB agreed in 05/1998 on a joint venture for 3G development.

This cooperation resulted in 12/1998 in the founding of the 3GPP (Third Generation Partnership Project). Many other major organizations participate in the 3GPP for development and promotion of 3G standards. Since then, 3GPP is responsible for the production, testing and further development of a global UMTS standard (often referred to as WCDMA in Asian areas).

18



Start of UMTS Standardization

GSM900/1800/1900

GSM-R, UMTS

• UMTS: GSM

successor standard

• devised in SMGs

(Special Mobile Groups)

ETSI• 1996/97: studies on UMTS

(1. Phase UTRA conception)

• 06 - 12/97: Evaluation of

5 Concepts

(2. Phase UTRA conception)

• 01/98: Select � & � concept

• 01 - 06/98: Harmonisation

� FDD & TDD

(3. Phase UTRA Conception)

• 06/98: Submission of UTRA

RTT proposal to ITU

• 05/98: Harmonisation by

ETSI / ARIB

12/98: 3GPP foundedfor

„developing, approving & maintaining

common UMTS specification“

Fig. 11

19


3GPP: Third Generation Partnership Project

In December 1998, five regional standards organizations (Japan: ARIB and TTC, Europe: ETSI, South Korea: TTA, USA: T1) agreed to found a new global standardization body. The objective of this body, known as 3GPP, is the joint standardization, testing and continued development of UMTS.

The cooperation between many of these globally important standards organizations is intended to assure that UMTS can establish itself as the dominating 3G standard thereby facilitating global roaming and a genuine mass market for 3G.

The 3GPP guidelines were completed by March 1999.

From the year 2000 on, the remaining GSM/EDGE standardization work has been taken over by 3GPP from the ETSI.

3GPP members

3GPP distinguishes between "organizational partners“, "market representation partners" and "observership status“.

Organizational partners delegate experts to 3GPP to work on the development of the standard. Market representation partners can make submissions to 3GPP, and engage in the investigation of market demands, services, compilation of studies, etc.

Observership status is given to organizations with access to the 3GPP committees but without any voting power.

Since the founding of the 3GPP many other organizations have agreed to active involvement in the project.

For instance, by the beginning of the year 2000, the CWTS (China) joined as an organizational partner; the UMTS Forum, GSM Association, GSA,UWCC and Ipv6 Forum as market representation partners MPRs and TIA and TSACC are engaged under observership status. Several other organizations joined 3GPP in the following as MPRs.

20



3GPP3rd Generation

Partnership Project

ETSIEuropean Telecommunication

Standards InstituteARIB/TTC

Association of Radio Industries

& Business / Telecommunication

Technology Committee, Japan

CWTSChina Wireless

Telecommunications

Standards

UMTS

Forum

GSM

Association

MPR: Market Representation

Partner

Organisational Partner

Observership status

GSAGlobal Mobile Supplier

Association

UMTS

Standardization

TIATelecommunication

Industry Association,

USA

TSACCTelecommunication

Standards Advisory Council

of Canada

ANSI T1Committee T1

Telecommunications

TTATelecommunications Technology

Association, South Korea

UWCCUniversal Wireless

Communications

Consortium

IPv6

Forum

WMFWireless Multimedia

ForumMWIF

Mobile WirelessInternet Forum

3G.IPForum

ACIFAustralian Communications

Industry Forum

Fig. 12

21


3GPP structures

3GPP originally has been divided into a project coordinating group (PCG), originally four, now five technical specification groups TSG's and many working groups WG's.

The PCG coordinates the work of the various TSG's and WG's.

The TSG's are writing the standard – i.e., the recommendations for UMTS and GSM/EDGE.

There are TSG's for each of the following UMTS topics: "Radio Access Network", "Service & System Aspects", "Core Network" and "Terminals"."

A fifth TSG has been created in July 2000: "GERAN" (GSM/EDGE Radio Access Network). Its principal responsibilities will be the maintenance and development of GSM Technical Specifications and Technical Reports, including GSM evolved radio access technologies such as GPRS and EDGE.

The Working Groups are working out studies regarding different aspects of the standard. The studies are used by the TSG's as a basis for drafting the recommendations.

TSG: TechnicalSpecification Group

PCGProject Co-ordinating Group

3GPP

Structure

Source: 3GPP

RAN WG 1Radio Layer 1

specification

T WG 1Mobile Terminal

Conformance testing

CN WG 1MC/CC/CS (Iu)

SA WG 1Services

GERAN WG 1Radio Aspects

RAN WG 2Radio Layer 2 & 3

(RR) spec.

T WG 2Mobile Terminal

Services & capabilities

CN WG 2CAMEL

SA WG 2Architecture

GERAN WG 2Protocol Aspects

RAN WG 3Iub, Iur, Iu spec. &

UTRAN O&M requirem.

T WG 3USIM

(Universal SIM)

CN WG 3Interworking with

External Networks

SA WG 3Security

GERAN WG 3BS Testing and O&M

RAN WG 4Radio performance &

Protocol aspects

CN WG 4MAP/GTP/BCH/SS

SA WG 4Codec

GERAN WG 4MS testing

CN WG 5OSA (Open

Service Architecture)

SA WG 5Telecom Management

TSG RANRadio Access

Network

TSG TTerminals

TSG CNCore Network

TSG SAServices & System

Aspects

TSG GERANGSM EDGE

RAN

Fig. 13

22



The UMTS Standard

The UMTS (3G) Standard drafted by the 3GPP is based on the success and experiences of the GSM Standard.

The first UMTS (3G) Release – completed at the beginning of the year 2000 and known as the UMTS Annual Release 1999 – is based in many areas on the GSM Annual Release 1999. This is true in particular for the Core Network (CN) and the service aspects. There are also very many '3G-only' specifications. This refers particularly to the implementation of the UTRA radio interface.

The UMTS (3G) Standard is divided into different series (Series 21 to 34). These are in turn subdivided into individual specifications.

Recommendations of the UMTS (3G) Standard as known as technical specifications. Their numbering is derived from the numbering system of the GSM Standard. A technical specification (TS) is numbered as "3G TS ab.cde", where "ab" represents the series and "cde" the particular specification. Up to 1000 specifications are therefore possible in any one series. This is a larger scale than is the case for GSM.

Specifications derived from the GSM Rel. '99 are numbered after the corresponding GSM series plus 20. The "c" in the TS is set to "0" here. For example: 3G TS 27.007 is a technical specification deriving from the GSM Rec. 07.07.

The numbering system is explained in detail in the 3G TS 21.101.

The 3G TS 21.101 also provides an overview of all series and individual 3G technical specifications.

23



The UMTS Standard

GSM

Rel. 99Specification

„3G only“Specification

3G

Release 1999Specification

3G TS ab.cde

TS: Technical Specification

ab.cde: Series . Number

Numbering:

Derived from GSM-Spec.:

GSM-Series +20; c = 0e.g.: GSM 07.07 � 3GTS 27.007

Fig. 14

24


3G Series

The UMTS specifications are divided into a total of 15 series.

Each of the series treats a particular aspect of the UMTS Standard.

21 series: Requirement specifications (overview: preliminary nature)

22 series: Service aspects

23 series: Technical realization

24 series: Signaling protocols (UE - CN network)

25 series: UTRA aspects

25.100 series: UTRA radio performance aspects

25.200 series: UTRA radio aspects (physical layer 1 of UTRA)

25.300 series: UTRA radio interface architecture, layer 2 and layer 3 aspects

25.400 series: UTRA network aspects (Iub, Iur, Iu Interface)

26 series: Codecs (speech, video, etc.)

27 series: Data (functions for support of data applications)

28 series: Signaling protocols (RSS - network part)

29 series: Signaling protocols (NSS)

30 series: Program management (3GPP plans and work programs, etc.)

31 series: UIM (User Identity Module)

32 series: Operation and Maintenance

33 series: Security aspects

34 series: Test specifications

35 series: Confidentiality & integrity algorithms

Work on the "classical" GSM series 1 - 12 is closed. The remaining work on GSM/EDGE is done by TSG "GERAN" in the series 41 – 55, which are build up in analogy to the 21 - 35 series of UMTS.

25



3G TS: Series

34-Series: Test Specifications

33-Series: Security Aspects

32-Series: Operation & Maintenance

31-Series: USIM

30-Series: Program Management

29-Series: Signalling Protocols (NSS)

28-Series: Signalling Protocols (RSS - CN)

27-Series: Data

26-Series: Codecs (Speech, Video,..)

25-Series: UTRA Aspects

21-Series: Requirements Specifications (Overview, Infos,..)

22-Series: Service Aspects

23-Series: Technical Realisation

24-Series: Signalling Protocols (UE - CN)

35-Series: Confidentiality & integrity algorithms

TS: Technical Specifications

� GSM Series 1 - 12

� closed with Rel. ‘99

� GERAN: Series 41 - 55

� R4 (Rel.`2000) onwards

� GSM Series 1 - 12

� closed with Rel. ‘99

� GERAN: Series 41 - 55

� R4 (Rel.`2000) onwards

Fig. 15

26


2.2 3G / UMTS: 4 Zone Concept / Data Rates

The 4-zone concept in UMTS is based on the IMT-2000 specifications of the ITU. The concept defines three terrestrially supplied zones (in-building, urban, suburban/rural) and one zone (global) supplied by MSS's (Mobile Satellite Systems).

Zone 1: Indoor

Zone 1 is made up of pico cells and is used for servicing large offices, domestic households, floors in skyscrapers, the stock exchange, etc. The service radius of the pico cells is in the order of several tens of meters – i.e., small areas with high user densities and little mobility (max. 10 km/h) are supplied. Coupled with the restricted mobility are high (ITU) requirements on the transfer rate (up to 2 Mbit/s). Up to 2 Mbit/s are theoretically possible with UMTS in Zone 1.

Zone 2: Urban

Zone 2 is made up of micro cells and is used to serve so-called hot spots. These are inner city areas, public places, sports stadiums, exhibition and trade fair halls, airport terminals, railway stations, etc. The service radius of the micro cells is in the order of several hundreds of meters – i.e., relatively small areas with high user densities and low (max. 10 km/h) mobility are supplied. Up to 2 Mbit/s are theoretically possible with UMTS in Zone 2.

Zone 3: Suburban/rural

Zone 3 is made up of macro cells and is used for servicing suburban and rural areas. The service radius of the macro cells is in the order of several kilometers – i.e., relatively large areas with medium-sized user densities and medium (max. 120 km/h) or high (max. 500 km/h) mobility are supplied. The ITU requested up to 384 kbit/s for medium speed support. In UMTS theoretically up to 480 kbit/s are foreseen for Zone 3. High mobility (max. 500 km/h), for which the ITU requested to support up to 144 kbit/s is not supported in initial UMTS.

Zone 4: Global

Zone 4 globally covers all rural, non-built-up, sparsely populated areas: In other words, everything not covered by zones 1 – 3. This includes the oceans, deserts, mountainous terrain and the polar regions. MSS's are to service these areas. They can provide coverage for areas ranging from several tens of kilometers (via beam spots) to areas with a radius of up to several thousands of kilometers. Supply for the highest mobility (up to 1000 km/h) should be possible at data rates of up to 144 kbit/s (ITU requirement). Satellite UMTS (S-UMTS) has been discussed but never developed.

27



Zone 4: Global

Zone 3:

Suburban / Rural

Zone 2:Urban Zone 1:

IndoorPicoCellMicro

Cell

MacroCell

MSS

UMTS-

concept:

4 zones

max.

data rate144 kbit/s 384 kbit/s 2048 kbit/s

max.

speed

144 kbit/s

1000 km/h 120 km/h 10 km/h500 km/h

Fig. 16

28


Data rates and applications: UMTS compared to other transmission systems

In the indoor area, UMTS with its greater flexibility and faster data rates will assume control of the functions currently implemented by 2nd generation systems such as DECT, W-PBX and WLL. These 2G systems work in TDD mode (Time Division Duplex) and theoretically enable data rates of more than 100 kbit/s. UMTS has a TDD mode for this area that allows data rates of up to 2 Mbit/s. These speeds provide capability for image transmission that goes beyond the performance of previous applications (for example, video-on-demand, games-on-demand, video conferences, etc.). Applications that were previously inconceivable or extremely unlikely are now possible in this area.

Fixed network links or special mobile transmission systems such as WLAN (Wireless Local Area Network) or MBS (Mobile Broadband Systems) will still be required in the future for applications with extremely demanding capacity requirements. These systems are either in the trial or development phases (4G).

Cellular 2G systems such as GSM, IS-95, D-AMPS or PDC and 3G PMR systems such as TETRA are used in the outdoor area – i.e., suburban and rural areas with low to medium speeds. These 2G systems work in FDD mode (Frequency Division Duplex). Generally only voice and data transfer rates of about 10 kbit/s (in GSM Phase 2+ with over 100 kbit/s) are reached. UMTS possesses an FDD mode for this area that allows data rates of up to 480 kbit/s for medium speed in outdoor areas.

Terrestrial, cellular UMTS components (TDD and FDD modes) will therefore be responsible for the functions of today's 2G indoor systems (TDD mode) and 2G outdoor systems (FDD mode). Much higher data rates are possible with the new generation.

3G systems will also represent a quantum leap in the number and variety of potential applications in the global area, which with 1G and the first 2G MSS systems could only offer relatively low data rates.

29



Source: UMTS Task Force Report

• Applications • Data rates• 2G / 3G comparison

UMTS

MBS(Mobile BroadBand System)

100

1

0.1

0.01

10

Fix

ed

netw

ork

office / floor Building, halls Hot Spots Pedestrian Vehicles

Indoor

WLAN

UMTS

2G FDDcellular systems (GSM, IS-95,..)

2G TDD(DECT, W-PBX, WLL)

Fixed networkTerminal

Da

ta r

ate

s [

Mb

it/s

]

stationary stationary stationary Low mobility High mobility

Outdoor

(FDD & TDD Services)

3G

Fig. 17

30


2.3 UMTS Licenses

Licensing

The licensing of UMTS was commenced in Finland in 03/1999. The remaining EU15 nations, other Western and Central European countries, Japan and South Korea, South Africa, Australia and New Zealand have followed in 2000 and early 2001.

Different licensing methods are used. A number of countries (e.g. Finland, Spain) prefer the distribution of licenses (more or less) free of charge, using a so-called "beauty contest" to find out the most reliable network operators for the restricted number of licenses.

Most other countries (e.g. Germany, the United Kingdom and the Netherlands) preferred different auction systems (open and closed). The acquisition of licenses is linked in most countries to different conditions. The conditions include guarantees for commencement of UMTS operation and the requisite service level with UMTS after a particular time (e.g., 50% of the population after 5 years). The lifetime of the licenses will be limited to 15 years in most cases. In Germany they are limited to 20 years. Regional licenses are not excluded. In general, however, operators prefer national licenses.

Licenses

2 x 60 MHz are available for paired bands (FDD) and a total of 35 MHz for unpaired bands (TDD) for the EU15. There are therefore 12 packets for paired bands and 7 packets for unpaired bands to be allocated for use with the UMTS 5-MHz bandwidth. The UMTS Forum specified a minimum of 3 packets for paired bands (i.e., 2 x 15 MHz) and 1 packet for unpaired bands (i.e., 1 x 5 MHz) per operator for optimum deployment of UMTS. If licenses have been granted in this way (2 x 15 MHz for paired band), this implies a maximum of 4 operators in each country. For this reason, licenses with 2 x 10 MHz for paired bands have been also allocated in countries with high population densities, thereby allowing 5 or 6 licenses per country.

31



UMTS

Licensing

Licensing in:� Finland 03/99

� Spain, GB: 1Q2000

� NL, D, F, I: 3Q2000

� EU15: closed until

end of 2000

� Japan: 1Q2001

frequency range [MHz]19001920 1980 2010 2025 2110 2170

Licenses (EU15):� 2 x 60 MHz paired band (FDD)

� 35 MHz unpaired (TDD)

� bandwidth: 5 MHz

� � 12 FDD packets + 7 TDD packets� UMTS Forum SAG requests per operator:

min. 2 x 15 MHz FDD + 1 x 5 MHz TDD

� EU15: 4 - 6 Licenses� (e.g.: F, Fin., Spain: 4; GB, NL: 5; D: 6)

Licenses (EU15):� 2 x 60 MHz paired band (FDD)

� 35 MHz unpaired (TDD)

� bandwidth: 5 MHz

� � 12 FDD packets + 7 TDD packets

� UMTS Forum SAG requests per operator:

min. 2 x 15 MHz FDD + 1 x 5 MHz TDD

� EU15: 4 - 6 Licenses� (e.g.: F, Fin., Spain: 4; GB, NL: 5; D: 6)

UMTS FDD (UL) UMTS FDD (DL)UMTS

TDDUMTS

TDD

Licensing methods / conditions� „free of charge“ / “beauty contest”

� (e.g. Finland, Spain)

� Auctioning: e.g. GB, D, NL, I

� annual fee: e.g. France

� available (mostly) for 15 years

Fig. 18

32

Chapter 2

UMTS Evolution

UMTS Evolution Siemens

Contents

1 Background & Principle 23

1.1 Evolutionary Path: GSM to UMTS 34

1.2 GSM & UMTS Evolution 78

1.3 Evolution: Data Transmission 190

2 Exercise 1113

3 Solution 1317

UMTS Evolution

1


1 Background & Principle

Background & Principle

UMTS Evolution

GSM

UMTS

Phase1/2

Phase2+

Release3

Release4

Fig. 1

2

Siemens UMTS Evolution

1.1 Evolutionary Path: GSM to UMTS

Original UMTS planning

The original considerations regarding a 3rd generation of mobile communications at the start of the 1990's represented a decisive leap in comparison to the 2nd generation. The general opinion expressed at the so-called "zero meeting" held by the ETSI SMG5 responsible for UMTS conception and coordination in December 1991 was that all downward compatibility of UMTS with GSM be avoided. UMTS was to be a system fully independent of GSM in order not to limit the capability of UMTS with compromises regarding the existing GSM infrastructure.

This point of view was revised in the mid-1990's. The costs of research, standardization and development of UMTS exceeded those of GSM many-fold. Moreover, GSM proved to be much more successful than even the most optimistic forecasts predicted. GSM networks providing total coverage were erected not only in Europe, but also in most other countries in the world. In view of this situation, it would have been extremely expensive with little chance of success to establish UMTS networks that are fully incompatible with existing GSM networks.

Downward compatibility of UMTS

The UMTS strategy was changed with the publication of the ETSI GMN (Global Multimedia Mobility) Reports 1996.

UMTS networks are now to be designed on the basis of the existing GSM infrastructure and are to be downward compatible with GSM. UMTS has a modular design for this reason. The first module to be centrally changed for the UMTS introduction with regard to GSM is the broadband radio interface. Further modifications are to follow in subsequent phases.

3

UMTS Evolution Siemen


Problems:• UMTS-costs (research, standardisation, development) >> GSM• creation of GSM-incompatible networks is not promising

Capabilities

Zeit2000 20021990

GSM

UMTS

Evolutionary path:

GSM to UMTS Original vision:

quantum leap from

GSM to UMTS

Fig. 2

4


The evolutionary path: GSM to UMTS

The ETSI GMM (Global Multimedia Mobility) Report from 1996 pointed the way for the development not only of UMTS, but also of GSM. GSM was to be further evolved in the GSM Phase 2+ in such a manner that its capabilities progressed toward UMTS. The GSM network and protocol structures were developed so that they can be used as a platform not only for high level GSM services, but also for UMTS.

UMTS will continue the GSM success story. The existing infrastructure of the GSM operators will be more intensively used, and also for UMTS. This reduces the financial risks involved in the introduction of UMTS. In other words, the 2G investments will continue to be utilized.

The experience gained by GSM with regard to the core network and the protocols/procedures (e.g., the MAP protocol, call control, mobility management, handover, etc.) will also be used either directly or in a modified form. This approach will also reduce the risks involved in the technical 3G implementation.

Also of great importance is the introduction of dual and multimode terminals that will be able to use the entire area serviced by GSM from the very beginning by handover between UMTS and GSM, thereby paving the way for UMTS (reduction of 3G risks).

This new evolutionary plan gives 2G operators a chance to reconfigure their networks for upward compatibility, and UMTS operators can avail of the downward compatibility to assure successful UMTS launching.

In this way GSM will slowly evolve along a migration path toward the original objectives of UMTS to obtain the smoothest possible transition from the 2nd to the 3rd generation of mobile communications.

5



Reducing 3G Risks !• Minimize technical risks

• Minimize implementation risks

Save 2G Investments!• Technical investments of operators

• sales/marketing investments

• Based on global GSM success & experience

• Common Core Network (for GSM & UMTS)

• based on GSM Non-Access Stratum protocols (CM, MM, SM,..)

• based on GSM CN protocols (MAP)

• re-use GSM Supplementary Services

• production experience of 2G equipment vendors– shorter paths for marketing 3G products– faster reduction of costs

ETSI GMM Report 1996:

UMTS downward compatible

Upwardcompatible

Downwardcompatible2G2G 3G3G

Migration path for 2G operators toward 3G

GMM: Global Multimedia Mobility

Evolutionary path:

GSM to UMTS

Fig. 3

6


1.2 GSM & UMTS Evolution

The original plans for GSM in the 1980's included all aspects of a 2G standard. In 1988 it became clear that this was not possible in the specified time frame. For this reason, GSM was released in a preliminary version in 1990/91 as GSM Phase 1.

GSM Phase 1

Phase 1 contains everything required for the operation of GSM networks. Speech data transfer is the core focus. Data transfer is defined, too (0.3 - 9.6 kbit/s). Only a few supplementary services are included.

GSM Phase 2

After Phase 1completion, the GSM Standard was fully revised. Phase 2 includes a wide range of supplementary services comparable with the ISDN standard.

GSM Phase 2+

Phase 2+ enhances in Annual Releases (`96, `97, `98, `99) the GSM standard and prepares the UMTS introduction. Especially the GSM Core Network CN is enhanced to be used as UMTS CN at UMTS start. Major Phase 2+ aspects are IN services, flexible service definition, packet data transfer, high data rate transmission and improved voice codes. GSM is limited by the narrowband radio access, the radio resource efficiency and a lack of additionally available frequency bands.

UMTS Release `99 (also: Release 3)

With GSM Rel. `99, a handshake with the first UMTS Release (Rel.. `99 or Rel. 3) according to many CN and service aspects is performed. UMTS introduces a new, broadband radio access optimized for packet data transmission up to 2 Mibt/s.

UMTS Release 4

Unlike GSM Phase 2+, the enhancement of UMTS is not performed in annually steps. Enhancements should be possible in flexible time schedules. Rel. 4 (late 2001) introduces e.g. important CN modifications (bearer independent signaling flow) and the Low Chip Rate LCR TDD mode as a third radio access option.

UMTS Release 5, 6, …

For UMTS Rel. 5 major CN modifications, i.e. the IP Multimedia Subsystem IMS, are planed. New network elements and protocol structures are defined.

For the future modifications of the UTRAN toward an All IP RAN, enhancements of the radio resource efficiency, new frequency ranges (WRC'2000) and many more enhancements toward 4G are expected

7



GSM & UMTS

Evolution

Capabilities

TimePh1: TeleServices TS, BS max. 9.6 Kbit/s

Ph2: SupplementaryServices SS (= ISDN)

Phase

1

Phase

2

GSM

UMTS

Phase

2+

Release

4

Release

5

Release‘96

Release‘97

Release‘98

Release‘99

new SS, flexibleService Concept

(CAMEL, MExE,..),higher data rates

(HSCSD, GPRS, EDGE)new network elements

GSM Limits: • narrow-band radio access• resource efficiency• additional frequency bands

required

Release

3

new WCDMARadio Interface(large bandwidth,

Flexible data rates;optimized for PS);

new RAN

new CN solutions(R’4: CS domain

modificationR’5: IMS);

new RTT options(LCR-TDD)

��

close to original3G plans

IMS: IP Multimedia SubsystemLCR: Low Chip RateRTT: Radio Transmission Technology

Fig. 4

8


1.3 Evolution: Data Transmission

In Phases 1 / 2 GSM allows data transfers at 0.3 to 9.6 kbit/s. In Phase 2+ HSCSD, GPRS and EDGE are introduced to enhance the data transmission capabilities.

HSCSD: High Speed Circuit Switched Data

HSCSD defines bundling of up to 8 physical channels of one carrier. In practice, however, only up to 4 channels are bundled together due to CN restrictions. The maximum data rate per physical channel was increased from 9.6 kbit/s to 14.4 kbit/s, introducing a new codec. As a result, up to 57.6 kbit/s can be reached (theoretically up to 115.2 kbit/s). HSCSD, like conventional GSM, defines Circuit Switched CS data transfer. For HSCSD, only minor modifications to the GSM network were necessary.

GPRS: General Packet Radio Services

GPRS also allows bundling of up to 8 physical channels to one user. Four new Coding Schemes CS enable transfers at rates of 9.05 /13.4 / 15.6 / 21.4 kbit/s per physical channel. GPRS introduces Packet Switched PS data transmission, which allows efficient use of resources and direct access to Packet Data Networks PDN. New network elements and protocols, paving the way for UMTS, have been defined.

EDGE: Enhanced Data Rate for the GSM Evolution

EDGE introduces a new modulation method over the radio interface: 8-Phase Shift Keying 8PSK. This allows three times faster data transfer compared to the conventional GSM modulation method Gaussian Minimum Shift Keying GMSK. In this way, EDGE is used to enhance the performance of GPRS and HSCSD. Transmission at up to 69.2 kbit/s per physical channel is possible. Theoretically, data rate of up to 553.6 kbit/s are possible, granting ITU 3G requirements for Zone 3 (wide area mobility.

UTRA: UMTS Terrestrial Radio Access

In UMTS, UTRA introduces a new multiple access method (WCDMA), modulation principle (QPSK) and a 25 times larger bandwidth than GSM at new frequency ranges. New RAN network elements and protocols are defined. The maximum data transmission rate will be some 2 Mbit/s.

9



HSCSD: High Speed Circuit Switched Data

GPRS: General Packet Radio Services

EDGE: Enhanced Data rates for the GSM Evolution

Data TransmissionEvolution

• HSCSD, GPRS & EDGE: combining 1-8 TS

• HSCSD: Circuit Switched

• GPRS: Packet Switched; new Infrastructure

• EDGE: 8PSK instead of GMSK

• UMTS: UTRA (WCDMA) optimised for PS

8PSK: Phase Shift Keying

GMSK: Gaussian Minimum Shift Keying

UTRA: UMTS Terrestrial Radio Access

GSMPhase 1/2:

9.6 kbit/s

HSCSD:115 kbit/s

4 / (8) x 14.4 kbit/s

8 x21.4 kbit/s

8 x 69.2 kbit/s

max. D

ata

ra

te

EDGE:553 kbit/s

GSM Phase 2+

no newnetwork elements;

SW-changes

newnetwork elements &

protocol architecture:prerequisitefor UMTS !!

no newnetwork elements;

only changesin modulation

principle

GPRS:171 kbit/s

9,6 kbit/s

UTRA:1920 kbit/s

New:

• transmission

principles

(WCDMA)

• network

elements

• protocols

Fig. 5

10

Chapter 3

The UMTS Network

The UMTS Network Siemens

Contents

1 Release `99: Network Overview 23

2 Release `99 CN: CS Domain 69

3 Release `99 CN: Entities common to CS & PS Domain 1319

4 Release `99: PS Domain 1929

5 Release `99: UTRAN & UE 2637

6 Further Evolution: Release 4 & 5 3347

7 Exercise 4055

8 Solution 4765

The UMTS Network

1


1 Release `99: Network Overview

Enhanced GSM Phase 2+

Core Network

BSSGSM Base Station

Subsystem

UTRANUMTS Terrestrial

Radio Access Network

PSTN /

ISDNIntra- /

Internet

Co-existence of

GSM & UMTS

network elements

Release `99

Network Overview

UMTS

Network

GSM �� UMTS Evolution� saves investment costs

� reduces implementation risks

A IuGb

Um Uu

GSM GSM / UMTS UMTS

Fig. 1

2

Siemens The UMTS Network

Release `99: Network Overview

UMTS networks are based on GSM Phase 2+ Core Networks. This approach safeguards the investments made by today's GSM network operators and reduces the 3G implementation risks. The UMTS Terrestrial Radio Access Network UTRAN is connected to the enhanced Phase 2+ CN via Iu interface. The GSM Base Station Subsystem BSS and UTRAN can be connected to the same CN. The GSM Mobile Station MS is connected to the GSM BSS via GSM radio interface Um, the UMTS User Equipment UE to UTRAN via UMTS radio interface Uu.

An overview of the UMTS network architecture is given in TS 23.002.

The UMTS CN

The enhanced GSM Phase 2+ Core Network consists of a Circuit Switched CS Domain for speech, video telephony and real-time data transfer and a Packet Switched PS Domain for Non real-time data transfer. Furthermore, several network elements are necessary respectively optional for both domains, here determined as "Entities common to the CS & PS Domain".

An overview of the PS Domain is given in TS 23.060.

The UMTS Network Siemen

External

Networks

Network OverviewTS 23.002:

Network Architecture

CS Domain

PS Domain

Entities common

to the CS & PS Domain

GSM BSS

UTRANUE

RANRadio Access Network

CNCore Network

TS 23.060:GPRS

Fig. 2

3


The UMTS Network

CS Domain

The CS Domain of the UMTS CN consists of the following functions:

��MSC: Mobile Services switching Center

��GMSC: Gateway MSC

��SMS-GMSC: Short Message Services Gateway MSC

��SMS-IWMSC: Short Message Services Interworking MSC

��VLR: Visitor Location Register

��TC/IWF: Transcoding & Interworking function

PS Domain

The PS Domain of the UMTS CN consists of the following functions:

��GGSN: Gateway GPRS Support Node

��SGSN: Serving GPRS Support Node

��CGF: Charging Gateway Function

Entities common to the CS & PS Domain:

��HLR: Home Location Register

��AuC: Authentication Center

��EIR: Equipment Identity Register

��CSE: CAMEL Service Environment

UMTS Terrestrial Radio Access Network UTRAN & UE

The UTRAN consists of the following functions:

RNC: Radio Network Controller

Node B

UE: User Equipment

Remark: This list of UMTS functions is not complete (see TS23.002). Only the "most important" functions are shown. The listed functions are described in the following.


4


PSTN

X.25

ISDN

IP

TC: Transcoding

IWF: Interworking Functions

SM-SC: Short Message Service Centre

IWF/

TC

GMSC

GGSN

MSC /VLR

SGSN

HLR AuCEIRCSE

TRAU

B

S

C

BTS

R

N

C

BTS

Node B(n x BTS)

R

N

C

Node B(n x BTS)

Node B(n x BTS)

UE

CGF: Charging Gateway Function

CSE: CAMEL Service Environment

SMS-GMSCSMS-IWMSC

SM-SC

CGFBilling

System

CS Domain

PSDomain

GSM BSS

UMTS

Network

TS 23.002

UTRAN

Fig. 3

5


2 Release `99 CN: CS Domain

PSTN

X.25

ISDN

IP

IWF/

TC

GMSC

GGSN

MSC /VLR

SGSN

HLR AuCEIRCSEUTRAN

TRAU

B

S

C

BTS

R

N

C

BTS

Node B(n x BTS)

R

N

C

Node B(n x BTS)

Node B(n x BTS)

UE

SMS-GMSCSMS-IWMSC

SM-SC

CGFBilling

System

CS Domain

PSDomain

GSM BSS

Release `99 CN:

CS Domain

UMTS

Network

Fig. 4

6


3G MSC

The Mobile-services Switching Center MSC constitutes the interface between the radio system and the external fixed networks (ISDN / PSTN). The MSC performs all necessary functions in order to handle the circuit switched services to and from the Mobile Stations MS / User Equipment UE.

The MSC is an exchange which performs all the switching and signaling functions for MSs / UEs located in a geographical area designated as the MSC area. The MSC area is sub-divided into so-called Location Areas LA. The main difference between a MSC and an exchange in a fixed network is that the MSC has to take into account the impact of the subscribers mobility.

Several MSCs may be required to cover a country.

The MSC is connected to other network elements via the following interfaces (Examples):

��A-Interface: to the GSM Base Station Controller BSC

��B-Interface: to the VLR. The MSC is always associated with a Visitor Location Register. Therefore, the B-Interface is proprietary.

��C-Interface: to the HLR

��E-Interface: to other MSCs

��F-Interface: to the EIR

��Gs-Interface: to the SGSN (for common Mobility Management)

��Iu(CS)-Interface: to the RNC

Gateway MSC (GMSC): If a network delivering a call to the PLMN cannot interrogate the HLR, the call is routed to an MSC. This MSC will interrogate the appropriate HLR and then route the call to the MSC where the mobile station is located. The MSC which performs the routing function to the actual location of the MS / UE is called the Gateway MSC. The choice of which MSCs can act as Gateway MSCs is for the operator to decide (i.e. all MSCs or some designated MSCs).

Visited MSC (VMSC): For all the MSs / UEs in the MSCs area the serving MSC is regarded as Visited MSC.


7


ISDNMSC

VLR VLR

HLR

3G MSCMobile services

Switching Center

SGSN

IWF/

TC

TRAU

B

S

C

R

N

C

Iu(CS)

A

E

E

Gs

C

B

EIR

F MainMSCtasks:

• Switching• Handling CS Services• Call Setup / Release• Charging• Interfaces:

A, B, C, E, F,Gs, Iu(CS)

SMS-GMSCSMS-IWMSC

SM-SC

PSTN

GMSC:• PSTN/ISDN Interface • Interrogating HLR• routing to actual

UE location

GMSC:• PSTN/ISDN Interface • Interrogating HLR• routing to actual

UE location

GMSC

B

MSC:• always associated with VLR• control of geographical area:

MSC Area = 1 / severalLocation Area LA

• V(isited)-MSC for all UEsin MSC Area

MSC:• always associated with VLR• control of geographical area:

MSC Area = 1 / severalLocation Area LA

• V(isited)-MSC for all UEsin MSC Area

LA1 LA2

LA3 LA4

MSC Area

Fig. 5

8


Short Message Service SMS Gateway MSC (SMS-GMSC)

The SMS-GMSC acts as an interface between an external Short Message Service Center SMS-SC and the PLMN, to allow short messages to be delivered to MS / UE from the Service Center.

The choice of which MSCs can act as SMS Gateway MSCs is a network operator matter (e.g. all MSCs or some designated MSCs).

SMS Interworking MSC (SMS-IWMSC)

The SMS Interworking MSC acts as an interface between the PLMN and a SMS-SC to allow short messages to be submitted from MS / UE to the SMS-SC.

The choice of which MSCs can act as SMS Interworking MSCs is a network operator matter (e.g. all MSCs or some designated MSCs).

SMS-GMSC and SMS-IWMSC description can be found in TS 23.002.

SMS-GMSC

SMS-IWMSC

MSC /

VLR

SGSN

CS

Domain

PS

Domain

E

Gd

SM-SCShort MessageService Center

SMS-GMSCSMS Gateway MSC

SMS-IWMSCSMS Interworking MSC

all or some designatedMSCs can act as

SMS-GMSC/IWMSC(Network operator

dependent)

TS 23.002

External

Networks

Fig. 6


9


Visitor Location Register VLR

The Visitor Location Register VLR is responsible to aid the MSC with information on the subscriber, which are temporarily in the MSC service area. Therefore, in praxis it is always associated with an MSC.

The VLR request the subscriber profiles of subscriber with activated MS / UE in the MSC service area from the Home Location Register HLR and stores them temporarily. Temporarily means as long as the subscriber is not registered in a new MSC/VLR, even if he deactivated the MS / UE.

Additional to the semi-permanent subscriber data received from the HLR the VLR stores temporary data, e.g. information on the subscribers current location (the Location Area), the state of activation (Attached / Detached),...

Furthermore, the VLR is responsible for the initiation of security functions, e.g. the Authentication procedure, the start of ciphering and the TMSI re-allocation.

Examples of subscriber data in the VLR:

��MSISDN: Mobile Subscriber ISDN No.

��IMSI: International Mobile Subscriber Identity

��TMSI: Temporary Mobile Subscriber Identity

��LMSI: Local Mobile Subscriber Identity

��MSRN: Mobile Station Roaming Number

��LAI: Location Area Identity

��Authentication Parameter

��the identity of the SGSN where the MS has been registered

The organization of the subscriber data is outlined in TS 23.008.


10


* e.g. Authentication, Authorization,

Cipher & Integrity Start

MainVLRtasks:

• storing Subscriber profiles• Mobility Management• storing Location Information• controlling

Security Features*

for all UEs in MSC AreaVLR as „MSCs Data Base“:

• Subscriber Profile,e.g. IMSI, MSISDN,

Services (TS, BS, SS),..

• Temporary Subscriber Datae.g. LMSI, TMSI, MSRN,

Security Parameter, Location Information, IMSI attach/detach,..

VLRVisitor Location

Register

VLRMSC

B

HLR

D• Location Updates• Subscriber Profiles � VLR• Security Parameter

(via HLR � VLR)

• Interrogation (MSRN via HLR to GMSC)

• Location Updates• Subscriber Profiles � VLR• Security Parameter

(via HLR � VLR)

• Interrogation (MSRN via HLR to GMSC)

AuC

TS: Tele ServicesBS: Bearer ServicesSS: Supplementary ServicesMSRN: Mobile Station Roaming Number

IMSI: International Mobile Subscriber IdentityLMSI: Local Mobile Subscriber IdentityTMSI: Temporary Mobile Subscriber Identity

Fig. 7

11


Transcoding TC function

The Transcoding TC function is used to perform conversion between standard ISDN 64 kbit/s speech transmission and the UMTS Adaptive Multi-Rate AMR speech codec (Specs: 26-series).

The AMR speech coder is a single integrated speech codec with eight source rates from 4.75 kbit/s to 12.2 kbit/s, and a low rate background noise encoding mode. The speech coder is capable of switching its bit-rate every 20 ms speech frame upon command (TS 26.071).

Different to GSM, in UMTS the Transcoding function is not part of the Radio Access Network RAN. It has been defined as part of the UMTS Core Network CN.

Some optimization procedures allow it to be passed through, without transcoding, in the case of UE to UE communication for example, when double-transcoding would be performed for nothing.

Interworking Function IWF

The "classical" Core Network CN interfaces (e.g. A – G) are all Time Division Multiplexed TDM based (E1/T1). Different to this, The Iu interface between UTRAN and the UMTS CN is ATM-based. An Interworking Function IWF is necessary for conversion between TDM-based and ATM-based interfaces.

Remark: IWF and TC function can be stand-alone network elements or be integrated into the UMTS MSC, depending on the manufacturers / network operators decision / demands.

TCTranscoding

&

IWFInterWorking Function

VLR

IWF/

TC

TRAU

B

S

C

R

N

C

MSC

Iu(CS)

A

B

TCTranscoding

BlaBla

Bla

BlaBlaBla

RANRadio Access

Network

CNCore Network

• CN function in UMTS:part of MSC or standalone N.E.

• Conversion of Speech Data (CN �� RAN):using AMR speech codec

• CN: 64 kbit/s (ISDN)• RAN: 4.75 – 12.2 kbit/s (AMR)

AMR: Adaptive MultiRate

FGs

E

C

• Interworking: TDM �� ATM• all „classical“ CN-Interfaces (A-G):

TDM based (E1/T1 �� PCM30/PCM24)

• Iu(CS): ATM based

IWF

4.75 – 12.2 kbit/s 64 kbit/s (ISDN)

UTRAN

CN

Fig. 8


12


3 Release `99 CN: Entities common to CS &

PS Domain

PSTN

X.25

ISDN

IP

IWF/

TC

GMSC

GGSN

MSC /VLR

SGSN

HLR AuCEIRCSEUTRAN

TRAU

B

S

C

BTS

R

N

C

BTS

Node B(n x BTS)

R

N

C

Node B(n x BTS)

Node B(n x BTS)

UE

SMS-GMSCSMS-IWMSC

SM-SC

CGFBilling

System

CS Domain

PSDomain

GSM BSS

Release `99 CN:

Entities common

to CS & PS Domain

UMTS

Network

Fig. 9

13


Home Location Register HLR

The HLR is a database in charge of the management of mobile subscribers There may be one or more HLRs in a GSM PLMN.

The HLR is always associated with an Authentication Center AC (proprietary interface). It participates in different procedures, for e.g.:

��It sends all necessary data to the VLR.

��It supports the call setup in case of Mobile Terminating Calls MTC by sending routing information to the Gateway MSC (Interrogation).

��It transmits the security parameters from AuC to VLR on request

An HLR contains different semi-permanent mobile subscriber data, e.g.:

��IMSI: International Mobile Subscriber Identity

��MSISDN: Mobile Station International ISDN number

��Packet Data Protocol (PDP) address(es), e.g. IP address

��Services: Bearer Services BS, Tele Services TS, Supplementary Services SS

��a list of all the group IDs a service subscriber is entitled to use to establish voice group or broadcast calls

��CAMEL Subscription Information(s)

��Service Restrictions (e.g. roaming limitations)

Additionally, the HLR contains different temporary information of the mobile subscriber, e.g.:

��VLR and SGSN addresses

��Mobile Station Roaming Number MSRN

��SMS flags

The organization of the subscriber data is outlined in GSM 23.008.

Authentication Center AuC

The AuC is responsible to store the secret Keys of the subscribers and the security algorithm, which are necessary for the generation of the GSM and UMTS security parameters. On request of the VLR respectively the SGSN the AuC generates the security parameters. They are delivered via HLR to VLR / SGSN to enable Authentication, Ciphering and Integrity Check.

The AuC is always associated with an HLR (communication via a proprietary interface).


14


HLRHome Location Register

GMSC

GGSN

MSC /VLR

SGSN

HLR AuC

CS Domain

PS Domain

AuCAuthentication Center

C

Gr Gc

Subscriber data (Examples):• Semi-permanent Data: MSISDN, IMSI, Services

(BS, TS, SS), QoS Profile, CSI, Service Restrictions,..

• Temporary Data: VLR / SGSN address,

MS Non-Reachable flag, MSRN, SMS flags,..

• Subscriber Registration• Storing/Management

subscriber profiles• Deliver profiles to VLR/SGSN• Storing Location Information• (VLR / SGSN)• MTC: Deliver Routing

information to GMSC / GGSN• Associated with AuC

• Storing „secret Keys“(counterpart: USIM) &Security Algorithm

• Generating Security Parameter(GSM: Triples; UMTS: Quintets)

• Deliver Parameter to VLR / SGSN (via HLR)

• Associated with HLR

BS: Bearer ServiceTS: Tele ServiceSS: Supplementary ServiceCSI: CAMEL Subscription InformationQoS: Quality of ServiceIMSI: International Mobile Subscriber IdentityMSISDN: Mobile Station ISDN NumberMSRN: Mobile Station Roaming Number

D

Fig. 10

15

Siemens The UMTS Networ

Equipment Identity Register EIR

The EIR is an optional feature in GSM and UMTS. It has been defined to enable theft prophylaxis. Stolen or non-valid Mobile Equipment ME can be blocked from further usage.

The Equipment Identity Register EIR is the logical entity, which is responsible for storing in the network the International Mobile Equipment Identities IMEIs (TS 23.002). An IMEI clearly identifies a unique Mobile Equipment ME and contains information about the place of manufacture, device type and the serial number of the equipment.

The Mobile Equipment ME is classified as "white listed", "grey listed", "black listed" or it may be unknown as specified in TS 22.016 and TS 29.002.

The EIR performs IMEI Checks on VLR respectively SGSN request to check whether the ME is stolen or non-valid.

The EIR is connected to:

��the SGSN via Gf interface

��the VLR via F interface

• Storing IMEIs(counterpart: ME)on White / Gray / Black List

• Performing IMEI Checkon VLR / SGSN request

• optional network function

EIREquipment Identity Register

MSC /VLR

SGSN

EIR

CS Domain

PS Domain

F

Gf

IMEIInternational

Mobile stationEquipment

Identity

Fig. 11


16


CAMEL Service Environment CSE

For the introduction of CAMEL services, some network elements have to be enhanced and new functional entities have to be introduced (TS 23.078):

��GSM Service Control Function gsmSCF: functional entity that contains the CAMEL service logic to implement Operator-Specific Services OSS. It interfaces e.g. with the gsmSSF, the gprsSSF and the HLR.

��GSM Service Switching Function gsmSSF: functional entity that interfaces the MSC/GMSC to the gsmSCF. The concept of the gsmSSF is derived from the IN SSF, but uses different triggering mechanisms because of the nature of the mobile network

��GPRS Service Switching Function gprsSSF: functional entity that interfaces the SGSN to the gsmSCF.

��Home Location Register HLR: for subscribers requiring CAMEL support, the HLR stores different types of CAMEL Subscriber Information CSI (e.g. O-CSI for Mobile Originating Calls MOCs, T-CSI for Mobile Terminating Calls MTCs). The O-CSI is sent to the VLR at Location Update, on data restoration or if the O-CSI is updated by administrative action. The O/T-CSI is sent to the GMSC when the HLR responds to a request for routing information.

��MSC/VLR or SGSN: VLR or SGSN store the different CSI information as part of the subscriber data for subscribers roaming in the MSC/VLR or SGSN area. MSC or SGSN monitor the call states and communicate (internally) with the gsmSSF for further proceeding.

GMSC

GGSN

MSC /VLR

SGSN

HLR AuCgsm

SCF

Gn

E

gsmSSF

gsmSSF

gprsSSF

GSM Service Switching Function• interfaces MSC/VLR to gsmSCF• derived from IN SSF

• stores CAMEL Subscription Information CSI

GPRS Service Switching Function• interfaces SGSN to gsmSCF

GSM Service Control Function:

contains CAMELservice logic for

Operator-SpecificServices

MSC/VLR & SGSN:store CSI as part ofsubscriber profile

MSC/VLR & SGSN:

store CSI as part ofsubscriber profile

CSECAMEL Service

Environment

CS

Domain

PSDomain

Fig. 12


17


CAMEL Protocols & Interfaces

The Mobile Application Part MAP and the CAMEL Application Part CAP (TS 29.078) are used on the different interfaces (TS 23.078) applicable to CAMEL:

��HLR - VLR interface (D-Interface): On this interface the MAP is used to send the CAMEL related subscriber data to the VPLMN and for provision of Mobile Station Roaming Numbers MSRN. The interface is also used to retrieve subscriber status and location information of the mobile subscriber or to indicate suppression of announcement for a CAMEL service.

��GMSC - HLR interface (C-Interface): This interface is used at terminating calls to exchange routing information, subscriber status, location information, subscription information and suppression of announcements. The O/T-CSI that is passed to the IPLMN is sent over this interface using the MAP.

��SGSN / MSC or GMSC – gprsSSF / gsmSSF interface: These are internal interfaces. These interfaces are described in the specification to make it easier to understand the handling of Detection Points DPs.

��gprsSSF / gsmSSF - gsmSCF interface (CAP Interfaces): On these interfaces the CAP is used by the gsmSCF to control a call in a certain gprsSSF / gsmSSF.

��gsmSCF - HLR interface (CAP Interface): On this interface the MAP is used by the gsmSCF to request information from the HLR. As a network operator option the HLR may refuse to provide the information requested by the gsmSCF.

��GMSC - MSC interface (E-Interface): On this interface the MAP is used to transfer control of a call from a VMSC back to a GMSC for optimal routing.

MAP

HPLMN

VPLMN

CAMELProtocols &

Interfaces

MSC/VLR

HLR

UE

gsmSSF

MSC/VLR

gsmSSF

CSE

gsmSCF

CSE: CAMEL Service Environment

gsmSSF: GSM Service Switching Function

gsmSCF: GSM Service Control Function

CAP: CAMEL Application Part

MAP: Mobile Application Part

O-CSI: CAMEL Subscription Information (MOC)

T-CSI: CAMEL Subscription Information (MTC)

Signalling

Data transfer

SGSN

gprsSSF

MAPCAP

Interfaces

O-CSIT-CSI

TS 23.078,29.078

Fig. 13


18


4 Release `99: PS Domain

PSTN

X.25

ISDN

IP

IWF/

TC

GMSC

GGSN

MSC /VLR

SGSN

HLR AuCEIRCSEUTRAN

TRAU

B

S

C

BTS

R

N

C

BTS

Node B(n x BTS)

R

N

C

Node B(n x BTS)

Node B(n x BTS)

UE

SMS-GMSCSMS-IWMSC

SM-SC

CGFBilling

System

CS Domain

PSDomain

GSM BSS

Release `99 CN:

PS Domain

UMTS

Network

Fig. 14

19

k

PS Domain - Main Concept

The PS domain uses a packet-mode technique to transfer high-speed and low-speed data and signaling in an efficient manner. The PS domain optimizes the use of network and radio resources. Strict separation between the radio subsystem and network subsystem is maintained, allowing the network subsystem to be reused with other radio access technologies. (TS 23.060)

Gateway GPRS Support Node GGSN

The GGSN is the first point of Packet Data Network PDN interconnection with a GSM / UMTS PLMN (i.e. it supports the Gi interface). GGSN functionality is common for GSM and UMTS.

The Gateway GPRS Support Node GGSN provides interworking with external Packet-switched Data Networks PDNs and it is connected with SGSNs via an IP-based backbone network (Gn interface). When the SGSN and the GGSN are in different PLMNs, they are interconnected via the Gp interface. The Gp interface uses the same protocols as the Gn interface. Additional security features are necessary.

The GGSN is the node that is accessed by the PDN due to evaluation of the Packet Data Protocol PDP address. It contains routing information for PS-attached users. The routing information is used to tunnel packet data to the MS / UE's current point of attachment, i.e., the Serving GPRS Support Node SGSN. The GGSN may request location information from the HLR via the optional Gc interface.

Furthermore, the GGSN is responsible for message screening and it is collecting charging data. The GGSN forwards the charging data via Charging Gateway Functionality CGF (Ga interface) to the Billing Center.

The SGSN and GGSN functionalities may be combined in the same physical node, or they may reside in different physical nodes.

20



GGSNGateway GPRS

Support Node

X.25

IPGGSNSGSN

HLR AuC

CGFBilling

System

PSDomain

SGSN

GnIP-based

Backbone

Network

SGSNother

PLMN

Gc

GaGp

Gi

• Interworking PLMN �� PDN (Gi)• Screening / Filtering• Storing Routing Information (current SGSN)• Requesting Location Information from HLR

(Gc optional; for MTC)• Routing Packets �� SGSN (Gn)• Collecting Charging Data & forwarding

to CGF (Ga)

TS 23.060

ExternalNetworks

Fig. 15

21


Serving GPRS Support Node SGSN

The Serving GPRS Support Node SGSN is responsible to provide service for all activated MS / UE in a certain geographical area, the so-called SGSN service area. The SGSN service area is subdivided into different Routing Area RA (a sub-set of the Location Area LA). A Routing Area consists of one or several cells.

The SGSN keeps track of the location of an individual MS / UE and stores it location (the Routing Area). It is responsible for the MS / UE Mobility Management (Location Updates, Attach, Paging,..). Furthermore, the SGSN performs security functions and access control.

The SGSN pulls the subscriber profiles via Gr interface from the HLR and stores it as long as the subscriber has not been registered in another SGSN.

It is signaling with MS / UE and GGSN to set up PDP Contexts to transmit packet data from MS / UE via RNC, SGSN and GGSN to external PDNs.

It is transmitting SMS via SMS IWF-/G-MSC (Gd interface) to the SM-SC.

It is controlling the QoS to be guaranteed for the subscribers service.

The SGSN also interfaces via the GPRS Service Switching Function gprsSSF with the GSM Service Control Function gsmSCF for optional CAMEL session and cost control service support.

The SGSN is connected to the GSM Base Station Subsystem BSS through the Gb interface and/or to the UMTS Terrestrial Radio Access Network UTRAN through the Iu interface.

It is interfaced with the MSC/VLR via Gs interface (optional) for Common Mobility Management. E.g. the SGSN may receive paging requests from the MSC/VLR via the Gs interface.

To provide Roaming it is connected via Gn / Gp (into other PLMNs) interface to other SGSNs. The Gp interface provides the functionality of the Gn interface, plus security functionality required for inter-PLMN communication. The security functionality is based on mutual agreements between operators.

The SGSN is collecting charging data and transmitting them via Ga interface to the Charging Gateway Function CGF.

The SGSN and GGSN functionalities may be combined in the same physical node, or they may reside in different physical nodes.

22



RA

1

RA

2

RA

3

RA

4

SGSN area

RA

5

RA

6

RA

7

GGSNSGSN

CGF

PSDomain

SGSN

GnIP-based

BackboneNetwork

SGSNother

PLMN

GaGp

EIRCSE

MSC /VLR

RNC

BSC

Iu(PS)

Gb

• Serving all UEs in SGSN area =1 / several Routing Area(s) RA

• Storing subscriber profiles(requested from HLR)

• Mobility Management, e.gUpdate Location, Attach, Paging,..

• Security & Access Control:Authentication, Cipher start, IMEI Check...

• Routing / Traffic-Management• Collecting charging data• …

UTRAN

GSM BSS

Gs

Gs Gr GdCAP

AuCHLRSMS-GMSCSMS-IWMSC

TS 23.060

SGSNServing GPRS

Support NodeLA

Fig. 16

23


Charging Gateway Functionality CGF

Charging in GSM / UMTS should be flexible and allow to bill according to the amount of data transferred, the QoS supported, and the duration of the connection. The GGSNs and SGSNs are collecting the charging data.

The Charging Gateway Functionality CGF provides a mechanism to transfer charging information from the SGSN and GGSN nodes to the network operator's chosen Billing Systems BS.

The Charging Gateway concept enables an operator to have just one logical interface between the CGF and the BS. The CGF may be supported in one of the following ways:

��-as a centralized separate Network Element, i.e. the Charging Gateway CG

��-as a distributed functionality resident in the SGSNs and GGSNs.

Support of the centralized or distributed CGF in a network is implementation dependent, and subject to vendor/manufacturer agreement. Regardless of the way in which the CGF is supported in the network, the functionality of the CGF is similar.

The main functions of the CGF are:

��-the collection of GPRS Charging Data Records CDRs from the GPRS nodes generating CDRs;

��-intermediate CDR storage buffering;

��-the transfer of the CDR data to the Billing Systems BS

The CGF acts as storage buffer for real-time CDR collection. It provides the CDR data to the BS.

Details of the Charging Gateway Functionality, the principles and transmission of CDRs and the protocol architecture of the Ga interface are given in TS 32.015.

24



GGSNSGSN

CGF

BillingSystem BS

PSDomain

CGFCharging Gateway

Functionality

TS 23.060& 32.015

ExternalNetworks

GaGa

Gn

GSNs

ChargingGateway

CG

GSN CGF BS

BS

• collect CDRs from SGSNs & GGSNs

• intermediate CDR storage buffering• CDR data transfer to the BS

The CGF can:

• reside in a separate N.E.:Charging Gateway CG

• be integrated in the GSNs

CDR: Charging Data Record

N.E.: Network Element

TS32.015:

Charging & Billing

for the PS Domain

TS32.015:

Charging & Billing

for the PS Domain

Fig. 17

25


5 Release `99: UTRAN & UE

PSTN

X.25

ISDN

IP

IWF/

TC

GMSC

GGSN

MSC /VLR

SGSN

HLR AuCEIRCSEUTRAN

TRAU

B

S

C

BTS

R

N

C

BTS

Node B(n x BTS)

R

N

C

Node B(n x BTS)

Node B(n x BTS)

UE

SMS-GMSCSMS-IWMSC

SM-SC

CGFBilling

System

CS Domain

PSDomain

GSM BSS

Release `99:

UTRAN & UE

UMTS

Network

Fig. 18

26


Radio Network Controller RNC

The UMTS Terrestrial Radio Access Network UTRAN is sub-divided into Radio Network Subsystems RNS. The Radio Network Controller RNC is the central controlling unit of a RNS. It is controlling itself and all the Node Bs of the RNS.

The RNC is connected via the following ATM based interfaces:

��Iub interface: to the connected Node Bs

��Iur interface: to neighboring RNCs

��Iu interface: to the Core Network CN

Due to different protocol stacks, the Iu interface can be sub-divided into an Iu(ps) interface and an Iu(cs) interface.

The Iu(ps) interface is used for data and signaling transmission to the PS Domain of the CN, the Iu(cs) interface is used for data exchange with the CS Domain.

The main task of the RNC is to perform Radio Resource Management RRM for all UEs in its service area. Therefore, it can be compared to the GSM BSC. Different to the GSM BSC, it is 100% autonomously responsible for all RRM decisions.

RRM means to be that the RNC is responsible for signaling with the UEs via Radio Resource Control RRC protocol, it is deciding about the allocation of resources, Handover to other cells and release of resources,...

The RNC is holding the RRC connection to the UEs as long as data have to be transmitted.

It is storing the UEs location information to transmit the data to the right location. The location information can be requested by the CN for Location Based Services.

It is responsible for reliable transmission over the radio interface, performing Backward Error Correction in acknowledged mode.

It is responsible for Ciphering / De-Ciphering and Integrity Check.

And it is responsible for many more WCDMA specific aspects shown in the following chapters and TS 25.3xx and 25.4xx series.

27



RNCRadio Network

Controller

RNCRadio Network

Controller

Node

B

RNSRadio

NetworkSub

system

UTRANIu(CS)

Iub

IurRNC

Node

B

Node

B

Iub

Node

B

SGSN

UE

IWF/ TC

MSC /VLR

Iu(PS)

Uu

PSDomain

CSDomain

• 100% autonomously RRM(e.g. Radio Resource Control, Access Control,

Admission Control, Handover Control,…)

• (De-)Ciphering & BEC (Layer 2 tasks)

• storing UEs location information

• RNS-Control (RNC & Node B’s)

• ATM Switching(Iu, Iur & Iub: ATM Interfaces)

• „WCDMA specific tasks“

Fig. 19

28


Node B

One or more Node B's are controlled and addressed by an RNC. A Node B is a physical unit for implementation of the UMTS radio interface. It is converting the physical transmission of the data from fixed network transmission (ATM based) to WCDMA transmission.

As a central transmission and reception site, it serves one or more UMTS cells. It is serving one UMTS cell in case of an omni cell with 360° service or, for example, 2, 3 or 6 sector cells with 180°, 120° and 60° service respectively.

The Node B is connected:

��via Iub interface to its controlling RNC

��via Uu interface to the UEs

To prepare the data for reliable transmission over the air interface Uu, the Node B performs many WCDMA specific aspects, which are shown in the following chapters and in the TS 25.3xx and 25.4xx series.

RNCRadio Network

Controller

Node

B

RNSRadio

NetworkSub

system

UTRAN

Iub

RNC

Node

B

Node

B

Node

B

UEUu

• Support of 1or several cells

• “WCDMA Transmission”

• ATM Termination

• Forward Error Correction FEC

• Radio Interface Measurements(Quality & Strength)

Node B

Node

BOmni-Cell

Sector-Cell

Node

BSector-Cell

Sector-Cell

Fig. 20

29



User Equipment UE

The User Equipment UE is responsible for similar functions as the GSM Mobiles Station MS, i.e. it is a device allowing a user access to network services.

It consists of the:

��Mobile Equipment ME, which means to be the Hardware and Software for WCDMA air interface transmission. The ME is identified by an International Mobile Equipment Identity IMEI.

��UMTS Subscriber Identity Module USIM, which contains data and procedures, which unambiguously and securely identify itself. These functions are typically embedded in a stand-alone smart card. This device is associated to a given user (subscriber license), and as such allows to identify this user regardless of the ME he uses. The USIM stores the personal identities (e.g. IMSI, MSISDN, PIN), security algorithm (for e.g. Ciphering, Authentication), the personal phone book, the USIM Application Toolkit USAT (TS 22.038, 31.111) and many more information.

The basic functions of the UE are given in the TS TS 23.101. More detailed descriptions are given in the TS 31 series.

UEUser Equipment

Node

B

Uu

RNC

MEMobile Equipment

USIMUMTS Subscriber Identity Module

• HW & SW for „WCDMARadio Transmission“

• Man-Maschine-Interface MMI

• Subscriber license

• Personal Identities(e.g.MSISDN, IMSI, TMSI, PIN,...)

• Security Algorithm & Keys(for Authentication, Ciphering,..)

• Personal phone book

• USIM Application Toolkit USAT

UE = ME + USIM

MSC/VLR

SGSN

TS 31.1xxseries

TS 23.101 &31series

Fig. 21

30



UMTS Network Summary (Release `99)

The UMTS PLMN consists of an UMTS Terrestrial Radio Access Network UTRAN, The User Equipments UE and an enhanced GSM Phase 2+ Core Network CN.

The Core Network consists of a Circuit Switched CS Domain for speech, video telephony and real-time data transfer, a Packet Switched PS Domain for Non real-time data transfer and Entities common to the CS & PS Domain.

The CS Domain of the UMTS CN consists of the following functions:

��MSC: Mobile Services switching Center

��GMSC: Gateway MSC

��SMS-IW-/G-MSC: Short Message Services Interworking-/Gateway-MSC

��VLR: Visitor Location Register

��TC/IWF: Transcoding & Interworking function

The PS Domain of the UMTS CN consists of the following functions:

��GGSN: Gateway GPRS Support Node

��SGSN: Serving GPRS Support Node

��CGF: Charging Gateway Function

Entities common to the CS & PS Domain:

��HLR: Home Location Register

��AuC: Authentication Center

��EIR: Equipment Identity Register

��CSE: CAMEL Service Environment

The UTRAN consists of the following functions:

��RNC: Radio Network Controller

��Node B

The UE consists of the following functions

��ME: Mobile Equipment

��USIM: UMTS Subscriber Identity Module

Remark: This list of UMTS functions is not complete. Only the "most important" functions are shown. A detailed overview is given in TS 23.002.

31



PSTN

X.25

ISDN

IP

IWF/

TC

GMSC

GGSN

MSC /

VLR

SGSN

HLR AuCEIRCSEUTRAN

T

R

A

U

B

S

C

BTS

R

N

C

BTS

Node B(n x BTS)

R

N

C

Node B(n x BTS)

Node B(n x BTS)

UE

SMS-GMSC

SMS-IWMSCSM-SC

CGFBilling

System

CS Domain

PS

Domain

GSM BSS

UMTS Network

Summary(Rel. `99)

Iu(CS)

Iu(PS)

Iub

Iur Ga

Gd

Gn

GcGr

GfCAP

CAP

E

FC/D

Gi

Uu

A

Abis

Gb

Um

Fig. 22

32


6 Further Evolution: Release 4 & 5

UMTS CN

GERAN UTRAN

PSTN /

ISDNIntra- /

Internet

Co-existence of

GSM & UMTS

network elements

Further Evolution

Release 4 & 5

UMTS

Network

GERAN: GSM/EDGE Radio Access Network

Fig. 23

33


3G modularity and further options

In 3G networks, the functions of the Core Network CN and the Radio Access Network RAN will be strictly separated. This separation will allow modularity in the composition of networks. The objective is to be able to combine any 3G CN with any 3G RAN. In addition, technical enhancements and upgrades of individual modules will be able to be introduced more easily, quicker and at less expensively due to the separation of functions.

Core Network CN options

In the initial phase of 3G, the different RANs are based on two different CN platforms: These are the GSM CN platform and the IS-41 platform. The different protocol architecture has been harmonized to enable the demanded modularity.

��The IS-41 CN has been used recently as platform for AMPS, D-AMPS and IS-95.

��The GSM CN has been used for the GSM BSS only.

��Pure IP CN solutions have been developed by the 3G.IP Forum / IETF. These ideas are incorporated now in UMTS Release 4 and 5 as additional CN options for enhanced 3G networks.

Radio Access Network RAN options

Different options for 3G RAN's have been developed and will be developed in 3G respectively for enhanced 3.5G networks.

��EDGE Classic / Compact is the 3G enhancements for GSM and D-AMPS

��UMTS includes the UTRA FDD and TDD mode, respectively from Release 4 on, two TDD modes (one with a High Chip Rate HCR and one with a Low Chip Rate LCR).

��MC-CMDA is used as IS-95 successor

��Different 3G proposals for MSS's

��3.5G enhancements of 3G systems toward higher data rates might be Wireless Local Loop WLL or Mobile Broadband Systems MBS

34



3G modularity

& future options

3G

Core

Network

e.g.

enhanced

GSM / IS-41,

or

R`4, R`5

UMTS CN

EDGE

MC- CDMA

Hiperlan-2,MBS,..strict separation

CN - RAN tasks

� flexibility in 3G

3G RAN

UTRA TDD HCR

UTRA TDD LCR

UTRA FDD

3G-MSS

Iu

Fig. 24

35


UMTS Release 4 CN

The UMTS CN CS domain is a central aspect of Release 4 modifications (TS 23.002). The intention of these modifications is a separation of the call control from the transport user the user data.

In UMTS Release 4, the (G)MSC/VLR functions split into two different entities:

��MSC Server: The MSC Server is responsible for e.g. Call Control CC and Mobility Management MM. It stores temporarily the subscribers data and takes over the "VLR functionality". It is interfacing and translating the user-network signaling (TS 24.008) and the network-network signaling and it is controlling one/several MGW(s) via Mc interface. Furthermore, it is collecting charging data (Call Data Records CDRs). As Gateway MSC Server, it is responsible for HLR interrogation.

��Media Gateway MGW: The MGW is responsible for bearer control and transmission resource management (e.g. QoS guarantee). It is responsible for the conversion of the data formats from CN internal, i.e. Nb interface (IP, ATM,…) to either Iu interface (ATM based) or external CS ISDN/PSTN networks. Additionally, the TC function is allocated to the MGWs interfacing Iu.

New Interfaces

��Nc: between MSC Server and (G)MSC Server for Bearer-Independent Call Control BICC.

��Mc: between CS-MGW and (G)MSC Server to separate between call control and bearer control. The ITU standard H.248 respectively its IETF standard equivalent Media Gateway Control MEGACO is used on Mc.

��Nb: between MGWs. Different options are possible on Nb for user data transfer and bearer control signaling (e.g. ATM, IP).

36



PSTN/ISDN

Bearer Level

Call Control

Level

MSCServer

HLR

GMSCServer

CS-MGW

CS-MGW

GERAN

UTRAN

Applications and Services

Mc (H.248/MEGACO)Mc

CAPCAP

Nb (e.g. ATM, IP)

Nc (e.g. BICC)

AIu

CD

Iu

A

UMTS CN R`4

CS Domain

MEGACO: IETF Media Gateway Control protocolH.248: ITU protocol for Media Gateway Control

PS Domain

unchanged

compared to R`99

PS Domain

unchanged

compared to R`99

R`4

TS 23.002

(G-)MSC Server:• Call Control

• Mobility Management

• MGW Control

• VLR functionality

• CDRs

• (HLR-Interrogation)

MGW:• Bearer Control

• Transmission Resource Management

• Data Format Conversion

• TranscodingCDR: Call Data RecordsBICC: Bearer Independent Call ControlMGW: Media Gateway

Fig. 25

37


UMTS Release 5 CN

In Release 5, it should be possible to transmit all data only via one PS domain (the so-called "All IP CN"). This PS domain can be split up logically into the GPRS CN with its well known network elements and an IP Multimedia Subsystem IMS, which is added to the GPRS CN like an external PDN (i.e. via Gi interface). Currently (late 2001) not all Release 5 network elements and functions are defined precisely.

For downward-compatibility reasons to GSM and UMTS Rel. `99 and Rel. `4 it might be necessary, to support additionally a CS domain.

Here some central Release 5 aspects / functions:

��Home Subscriber Server HSS: The HSS is used for mobility related aspects, very similar to the "classical" HLR (storing subscription and routing information).

��Media Gateway MGW: The MGW ensures interoperability and interworking between an All IP CN and the external fixed CS networks PSTN or ISDN. The MGW enables conversion from CS data transmission, e.g. voice transmission, to PS data transmission, e.g. Voice over IP VoIP. Echo cancellation and Transcoding functionality will take place in the MGW. The MGWs are connected via Gi interface towards the GGSNs.

��Media Gateway Control Function MGCF: The MGCF are used e.g. for MGW control, Call Control and Signaling Protocol Conversion from external SS7 to internal Session Initiation Protocol SIP.

��Call State Control Function CSCF: The CSCF are responsible e.g. for Session Flow Handling and Application Coordination. They are interfacing the IN / Application Server/ IN and they are responsible to collect charging data (Charging Data Records CDRs).

This description of Release 5 is regarded as a very first overview, giving an idea on the future UMTS options. It is not complete and needs to be extended in additional courses.

38



PSTN

UMTS CN R`5

IMS & PS Domain

HSS: Home Subscriber Server

MGW: Media Gateway

MGCF: Media Gateway Control Function

SIP: Session Initiation Protocol

Gi

UTRAN

R

N

C

NodeB

R

N

C

Iur

Iub

Iub

UE(USIM)

Uu

NodeB

NodeB

ISDN

SGSN GGSN

MGW

MGCF

X.25

IPR

R

R

R

R

R

CSCF

Iu

Intelligent & Application Servers

IMS: IP Multimedia Subsystem

CSCF: Call State Control Function

R: IP Router/Switch

CSE WAP •••

IP

Backbone

HSS

other

PLMN

R`5

TS 23.002

CSCF: • Session Flow Handling

• Application Coordination

• interfaces IN/Application

Servers

• CDR`s

HSS:• similar HLR

MGCF:• MGW control

• Call Control

• Signalling Protocol

Conversion (SS7 to SIP)

Fig. 26

39

Chapter 4

Security Features

Security Features Siemens

Contents

1 Overview 23

2 IMEI Check 79

3 (P-)TMSI Allocation 11195

4 Authentication 1521

5 Ciphering & Integrity Check 2735

6 Exercise 3747

7 Solution 4153

Security Features

1


1 Overview

IV) Application Domain Security:enables applications in the user & provider domain to

securely exchange messages (e.g. USIM ATK messages)

III) User DomainSecurity:

secures access to MS(e.g. PIN)

ME

HEHome

Environment

UMTS Security Features

Overview

TS 33.102:Security

Architecture

TS 33.102:Security

Architecture

SNServing

Network

ANAccess

Network

USIM

*also: User Services Identity Module

III)

I)

II) Network Domain Security:enables secure signaling data exchange &

protects against attacks on the wireline network

I) Network Access Security:provide users with secure access to 3G services &

protect against attacks on the radio access link

I)

II)

IV)

I)

I)

I)

Fig. 1

2

Siemens Security Features

UMTS Security Features: Overview

Five security feature groups are defined in UMTS (TS 21.133, 33.102, 31.120). Each of these feature groups meets certain threats and accomplishes certain security objectives:

I) Network Access Security

The network access security features, which are defined more precisely in the following chapter, provide users with secure access to UMTS services. Additionally, some of them protect the user and the network against attacks on the radio access link. Currently, User Identity Confidentiality (P-TMSI, TMSI Allocation), Entity Authentication (User / Network Authentication), Confidentiality (Ciphering), Data Integrity and Mobile Equipment Identification (IMEI Check) are defined as Network Access Security features.

II) Network Domain Security:

The network domain security features will be defined in future to enable nodes in the provider domain to securely exchange signaling data and protect against attacks on the wire-line network.

III) User Domain Security:

The user domain security features have been defined to enable secure access to the user equipment UE. Currently User-to-USIM Authentication (e.g. PIN; see TS 31.101) and USIM-Terminal Link security (restricting an ME to an authorized USIM by sharing a secret; see TS 22.022) are defined.

IV) Visibility and Configurability of Security:

The visibility & configurability of security features have been defined to enable the user to inform him whether a security feature is in operation. Additionally, the user should be able to decide whether the use and provision of services should depend on the security feature. Examples for visibility are the indication of access network encryption and the indication of the level of security (e.g. 3G or 2G network). Examples for configurability are enabling/disabling User-USIM authentication, accepting/rejecting incoming non-ciphered calls, setting-up or not setting-up non-ciphered calls, accepting/rejecting the use of certain ciphering algorithm.

3

Security Features Siemen


Network Access Security Features

� IMEI Check

� (P-)TMSI Allocation

� Authentication

� Ciphering

� Data Integrity Check

TS 21.133:Security Threats & Requirements

TS 33.102Security Architecture

TS 33.120Security Principles & Objectives

TS 21.133:Security Threats & Requirements

TS 33.102Security Architecture

TS 33.120Security Principles & Objectives

providing users withsecure access

to 3G services & protect againstattacks on the

radio access link

Fig. 2

4


Network Access Security Features

Similar to GSM, the UMTS system provides some mechanism to guarantee the network access security. Some features are still the same as in GSM, others have been enhanced, and also two new aspects have been additionally defined. The following network access security features have been defined in Rel. ’99:

IMEI Check: To prevent the usage of stolen or not allowed mobile equipment, the mobile equipment identification can be checked by the network. This feature remains the same as in GSM.

P-TMSI / TMSI Allocation: To guarantee the user identity confidentiality respectively the user location confidentiality the permanent user identity IMSI is normally not transmitted over the radio interface. The user is normally identified by the temporary identity TMSI / P-TMSI, by which he is known in the serving network. This feature remains the same as in GSM.

Authentication: In UMTS authentication is extended compared to GSM. Additionally to the User Authentication a Network Authentication is introduced. User Authentication is the property that the Serving Network SN checks the real identity of the user, preventing non-authorized access to the network. Network Authentication is a check whether the connected SN is really authorized by the user’s Home PLMN to provide him services. This includes the guarantee that this authorization is recent.

Ciphering: Ciphering prevents eavesdropping of user data and signaling over the radio interface. UMTS ciphering has been enhanced compared to GSM/GPRS.

Data Integrity Check: The Data Integrity Check has been introduced as a new security feature in UMTS. It provides security against unauthorized modification of signaling data respectively the change of data origin.

As in GSM/GPRS, user (temporary) identification, authentication and key agreement will take place independently in the PS and CS domain. User traffic will be ciphered using the cipher key agreed for the corresponding service domain. Control data will be ciphered and integrity protected using the cipher and integrity keys form either one of the service domains.

The Serving RNC has distribution functionality for the PS and CS domain. Two Iu signaling connections exist, but only one RRC connection.

5



PSTN

X.25

Network Access

Security Features

ISDN

IP

GMSC

GGSN

MSC/

VLR

SGSN

HLR AuCEIRNode B

UE=

ME+

USIM

Authentication

- User Authentication: network checks real user identity;

prevents misuse / misappropriation

of network resources / services

- Network Authentication: UE checks network authorisation

to provide service

Cipheringprevents eavesdropping of

user data / signaling on Uu

Data Integrity Checkprovides security against unauthorised

modification of signaling data /

change of data origin

IMEI Checkprevents usage of

stolen / not allowed ME

TMSI / P-TMSI Allocation- allocated by VLR / SGSN instead of IMSI

- protects user identity & location confidentiality

RNC

CS Domain

PS Domain

Fig. 3

6


2 IMEI Check


EIR:white / gray / black list

ME

IMEI Check

TS 23.002,23.003, 23.060,24.008, 29.002

TS 23.002,23.003, 23.060,24.008, 29.002

IMEI Check

ME

stolenMEnot

allowed

Fig. 4

7


IMEI Check

The IMEI Check is an optional feature, which can be used to prevent the usage of stolen or not allowed mobile equipment. This feature remains the same as in GSM.

The International Mobile Equipment Identity IMEI identifies uniquely a Mobile Equipment ME. Two versions of IMEI are defined (TS 23.003):

IMEI: The IMEI is composed of a Type Approval Code TAC (6 digits), a Final Assembly Code FAC (2 digits) to identifies the place of manufacture/final assembly, a Serial Number SNR (6 digits) as individual serial number uniquely identifying each equipment within each TAC and FAC and a Spare digit (1 digit) being zero, when transmitted by the MS / UE.

IMEISV (IMEI & Software Version number): The IMEISV is composed of the Type Approval Code TAC, Final Assembly Code FAC, Serial Number SNR and a Software Version Number SVN (2 digits), which identifies the ME software version number.

The security requirements of the IMEI are defined in 3GPP TS 22.016.

The IMEI should be surely stored in the ME. In certain cases, the Serving Network SN may request the UE to send it the IMEI. This shall be done only after authentication. In the case of emergency calls, no IMEI check should be performed.

The Equipment Identity Register EIR (TS 23.002) is responsible for storing the IMEIs in the network. The ME is classified as "white listed", "gray listed", "black listed" or it may be unknown as specified in TS 22.016 and TS 29.002.

The white list is composed of all number series of equipment identities that are permitted for use. The black list contains all equipment identities that belong to equipment that need to be barred. Besides the black and white list, administrations have the possibility to use a gray list. Equipment on the gray list are not barred, but are tracked by the network (for evaluation or other purposes).

An EIR shall as a minimum contain a "white list".

8



IMEI Check


6 digits = 24 Bit


2 digits = 8 Bit

SNRSerial Number6 digits = 24 Bit

Spare1 digit = 4 Bit

EIR:white / gray / black list

ME

IMEI: International Mobile station Equipment Identity

IMEI Check(optional)

SVN: Software Version Number

EIR:TS 23.002

EIR:TS 23.002


6 digits = 24 Bit


2 digits = 8 Bit

SNRSerial Number6 digits = 24 Bit

SVN2 digit = 8 Bit

IMEISV: IMEI & Software Version numberIMEI(SV):TS 23.003

IMEI(SV):TS 23.003

not in case ofemergency calls

Fig. 5

9


IMEI Check Procedure

The IMEI(SV) shall only be send after authentication (TS 33.102).

It shall be possible to perform the IMEI check at any access attempt, except IMSI detach, and during an established call at any time when a dedicated radio resource is available, in accordance with the security policy of the PLMN operator (TS 22.016).

The network shall terminate any access attempt or ongoing call when receiving any of the answers "black-listed" (i.e., on the black list) or "unknown" equipment (i.e. not on the white list) from the EIR. An indication of "illegal ME" shall in these cases be given to the user. Furthermore this is equivalent to an authentication failure hence any call establishment or any location updating is forbidden for the MS / UE, it cannot answer to paging, it is just allowed to perform Emergency Calls.

Emergency calls must never be terminated as a result of the IMEI check procedure.

The procedures to check the IMEI are described in TS 23.060 and TS 29.002.

IMEI Check

S-RNCUE

VLRSGSN

5) Check IMEI

[IMEI/IMEISV]

EIR

Authentication

2) Identity Request

3) Identity Response

[IMEI/IMEISV] 4) Identity Response

6) Check IMEI Ack.

[status: white/gray/black]

TS 33.102TS 33.102

IMEI Check• optional

• after authentication

• to be performed at any access attempt

& during established calls at any time

• not in case of emergency calls

• not at IMSI Detach

IMEI Check• optional

• after authentication

• to be performed at any access attempt

& during established calls at any time

• not in case of emergency calls

• not at IMSI Detach

1) Identity Request

[Identity Type]

Decision:Continue / Block

TS 29.002TS 29.002

Fig. 6

10



3 (P-)TMSI Allocation


(P-)TMSI Allocation

MSC/VLR

ME

TMSI

TS 23.002,23.003, 23.060,24.008, 29.002

TS 23.002,23.003, 23.060,24.008, 29.002

SGSN

P-TMSI

IMSI? ��

Mr. / Ms. XY!

Fig. 7

11


(P-)TMSI Allocation

A unique International Mobile Subscriber Identity IMSI shall be allocated to each mobile subscriber in the GSM system.

To achieve user identity confidentiality and user location confidentiality, the user is normally identified by a temporary identity (Temporary Mobile Subscriber Identity TMSI or Packet-TMSI) by which he is known by the Serving Network SN. To avoid user traceability, which may lead to compromise of user identity confidentiality, the user should not be identified for a long period by means of the same (P-) TMSI (TS 33.102). (P-)TMSI should be used at any Location Update Request, Service Request, Detach Request, connection re-establishment request, etc.

A (P-)TMSI has local significance only in the LAI or RAI in which to user is registered. Outside that area it should be accompanied by an appropriate LAII or RAI in order avoid ambiguities. The association between IMSI and TMSI / P-TMSI is kept by the VLR / SGSN in which the user is registered.

IMSI structure

The IMSI is composed of three parts: Mobile Country Code MCC, Mobile Network Code MNC and Mobile Subscriber Identity Code MSIN. The MCC (3 digits; CCITT administered) identifies uniquely the country of the mobile subscriber. The MNC (2 digits) identifies the Home PLMN of the mobile subscriber. The MSIN identifies the mobile subscriber within a GSM PLMN. The IMSI shall consist of numerical characters (O through 9) only. The overall number of digits in IMSI shall not exceed 15 digits.

(P-)TMSI structure

Since the (P-)TMSI has only local significance (i.e. within a VLR/SGSN area), the structure and coding of it can be chosen by agreement between operator and manufacturer in order to meet local needs. The P-TMSI / TMSI consists of 3 / 4 octets. It can be coded using a full hexadecimal representation.

12



Subscriber Identity

Packet-TMSI3 bytes SGSN

MCC3 digits

MNC2 digits

MSIN10 digits

MCC: Mobile Country Code

MNC: Mobile Network Code

MSIN: Mobile SubscriberIdentification Number

IMSIInternational Mobile Subscriber Identity

(15 digits)

TMSI4 bytes VLR

TMSI / P-TMSI• protect user identity confidentiality

• normally used in case of unciphered user id. transmission• allocated by VLR/SGSN

• local significance only in the LA/RA where the user is registered � accompanied by LAI/RAI • structure: operator-dependent

• Re-allocation as often as possible (only ciphered & in conjunction with other procedures)

TMSI / P-TMSI• protect user identity confidentiality

• normally used in case of unciphered user id. transmission

• allocated by VLR/SGSN

• local significance only in the LA/RA where the user is registered � accompanied by LAI/RAI • structure: operator-dependent

• Re-allocation as often as possible (only ciphered & in conjunction with other procedures)

TS 23.003TS 23.003

TS 33.102TS 33.102

UE

Fig. 8

13


(P-)TMSI Usage & Re-Allocation

The (P-)TMSI, when available, is normally used to identify the user on the radio access path, for instance in paging request, Location Area / Routing Area LA / RA Update Requests, Attach / Detach requests, Service Requests, Connection Re-establishment Requests,...

If the user cannot be identified by means of a (P-)TMSI, he is requested to identify himself by his permanent identity IMSI (“User Identity Request / Response”).

(P-)TMSI Re-Allocation (“(P-)TMSI Allocation Command / Complete”) is performed to allocate a new TMSI/LAI respectively P-TMSI/RAI pair to a user by which he may subsequently be identified on the radio access link. It should be performed after initiation of ciphering. The Re-Allocation is initiated by the VLR / SGSN.

The procedures P-(TMSI) usage & re-allocation procedures and mechanism are described e.g. in TS 23.060 and TS 31.102.

Examples of (P-)TMSI Usage / Re-Allocation

S-RNCUE

VLRSGSN

TS 33.102TS 33.102

TS 23.060TS 23.060

Paging

[(IMSI) / (P-)TMSI, Paging Cause]

PagingPaging

Initial Direct Transfer

[Establ. Cause*; old RAI/LAI & (P-)TMSI]

Initial UE Message NAS SignalingConnection

Establishment*

*e.g. LUP, RUP, Attach,Detach, Service Request

User Identity RequestIdentificationby (P-)TMSInot possible

User Identity Response

[IMSI]

User Identity Response

[IMSI]

(P-)TMSI Allocation Command(P-)TMSI

Re-Allocation (P-)TMSI Allocation Complete

Authentication & Cipher Start

NAS: Non-Access Stratum

(P-)TMSI Allocation Command

[(P-)TMSI + LAI/RAI]

(P-)TMSI Allocation Complete

User Identity Request

Fig. 9

14



4 Authentication


Authentication

MEHE

HomeEnvironment

SNServingNetwork

ANAccessNetwork

USIM AuC

TS 33.102TS 33.102

UMTSAuthentication:chosen to achieve

maximum compatibilitywith GSM security architecture

enhancedmechanism

& keys

Fig. 10

15


Authentication

In UMTS different to GSM both sides of the radio transmission check the correct identity of their counterpart. Not only the user identity is checked by the Serving Network SN. Additionally, the authorization of the SN to provide services is checked by the UE. Both, user and network authentication should occur at each connection set-up (TS 33.102).

So the objective of the Authentication process is to enable User Authentication similar to the GSM Authentication and additionally Network Authentication. Furthermore, the Authentication process provides the keys for Ciphering and Integrity Check to the User Equipment UE.

The authentication process should occur at each connection set-up between the user and the network.

It has been chosen in such a way to achieve maximum compatibility with the GSM security architecture and facilitate migration from GSM to UMTS.

Nevertheless, the security mechanism and keys for authentication have been enhanced significantly.

Providing Keys for:• Ciphering

• Signaling Data Integrity

HEHome

Environment

SNServingNetwork

ANAccessNetwork

USIM AuC

Authentication

Basics

Network Authentication:SN authorised by HE

to provide me services?

User Authentication:User identity alright?

New!

User & NetworkAuthentication

should occur at eachconnection set-up

User & NetworkAuthentication

should occur at eachconnection set-up

Fig. 11

16



Authentication – Basic Principle

For Authentication, Ciphering and Integrity Check a secret Key K is the pre-requisite. This secret Key K is shared between and available only to the USIM and the AuC in the user’s Home PLMN (TS 33.102). The function of K is similar to the GSM individual Key Ki, but it is of enhanced length (K: 128 bit; Ki: 64 bit).

Additionally, several different operator-dependent functions are necessary in the HPLMN’s AuC and in the USIM to generate the so-called Authentication Vector AV, which is necessary for Authentication, Ciphering and Integrity Check. AV is often also denoted as Quintet, in analogy to the GSM Authentication Triples.

Authentication is performed independently in the CS or PS domain.

If no Authentication Vectors correlated to the user are stored in the serving VLR/SGSN, VLR/SGSN are initiating the Authentication process with an “Authentication Data Request” via the HLR of the user’s HPLMN to the AuC. The “Authentication Data Request” shall include the IMSI. On basis of this order, the AuC generates a set of n Authentication Vectors AVs. This AVs are send back in an “Authentication Data Response” from Auc via HLR to the VLR/SGSN.

The VLR/SGSN stores the Authentication Vectors AVs and continues the Authentication sending some Authentication parameter to the USIM (“Authentication Request”). The UE stores the parameter, calculates keys for ciphering and integrity check and performs the network authentication. If the network authentication is successfully completed the UE answers with “Authentication Response” to the VLR/SGSN request, delivering a parameter for user authentication. VLR/SGSN perform user authentication.

If user authentication is successful, VLR/SGSN continue with connection set-up.

If user’s AVs are already stored in the VLR/SGSN, “Authentication Data Request” and “Authentication Data Response” are not necessary in the Authentication process.

17



Basic Principles

USIMHLR

AuC

VLR / SGSN

Authentication

Data Request [IMSI]

Authentication

Data Response

[AV(1..n)]

Authentication Request

[Authentication Parameter]

IMSI � K;f1...f5

Authentication Vector

/ Quintet

K: secret Key

SQN: Sequence Number

f1...f5: message authentication /key generating Functions

Ksecret Key

128 bit length

Visited PLMN Home PLMN

Authentication ResponseNetwork

AuthenticationUser

Authentication

Fig. 12

18


Authentication Vector AV

Each Authentication Vector consists of the following components (TS 33.102):

��a Random Number RAND, which is randomly generated, i.e. non-predictable. It’s length is 128 bit.

��an Expected Response XRES, which is used for User Authentication. It shall have a flexible length of 32 – 128 bit.

��a Cipher Key CK, which is necessary for Ciphering. It shall have a fixed length of 128 bit.

��an Integrity Key IK, which is used for Signaling Data Integrity Check. It’s length is 128 bit.

��an Authentication Token AUTN, which is used for Network Authentication. AUTN consists of three different parts, described later on. Its total length is 128 bit.

A set of n Authentication Vectors AVs is send on VLR/SGSN request from HLR/AuC to VLR/SGSN. The AVs are stored in the VLR/SGSN. Each AV is good for one authentication and key agreement (for ciphering & integrity check) between the VLR/SGSN and the USIM.

When the VLR/SGSN initiates an Authentication and key agreement, it selects the next AV and sends the parameters RAND and AUTN to the UE. The USIM checks whether AUTN can be accepted (Network Authentication) and computes a Response RES. RES is send back to the VLR/SGSN. The VLR/SGSN compare the received RES with the AV parameter XRES (User Authentication). If they are equal, User Authentication is successfully completed.

19



Authentication Vector AV

RANDRandom Number

128 bit

XRESExpected Response

32 - 128 bit

CKCipher Key

128 bit

IKIntegrity Key

128 bit

AUTNAuthentication Token

48 + 16 + 64 bit

USIM VLR / SGSN(store AV(1..n))


[RAND(i), AUTN(i)]

Authentication Response

[RES(i)]User Authentication:

CompareXRES(i) & RES(i)

� generate RES(i) = � f2(RAND(i),K)

� AUTN(i) for� Network Authentication

randomly generated,i.e. non-predictable

Used for data

encryptionUsed forintegrity check

RES: Response

• consisting of 3 parts• Used for network

authenticationUsed for userauthentication

Fig. 13

20


Generation of Authentication Vectors AVs

After receiving the “Authentication Data Request” from the VLR/SGSN, the AuC generates new Avs (TS 33.102). Every AV consists of the following five parameters:

Random Number RAND, Expected Response RES, Cipher Key CK, Integrity Key IK and Authentication Token AUTN.

Random Number RAND: The AuC starts with generating a fresh sequence number SQN and an unpredictable challenge RAND.

Expected Response XRES: The secret Key K, RAND and f2 are necessary to compute XRES. XRES = f2(K,RAND); f2 is a (possibly truncated) message authentication function. XRES is used for User Authentication.

Cipher Key CK: K, RAND and f3 are used to compute CK. CK = f3(K,RAND); f3 is a key generating function. CK is used for Ciphering.

Integrity Key IK: K, RAND and f4 are used to compute IK. IK = f4(K,RAND); f4 is a key generating function. IK is used for Signaling Data Integrity Check.

Authentication Token AUTN: K, RAND, SQN, AMF and f5 are necessary to compute AUTN. AUTN consists of three parts: AUTN = SQN * AK || AMF || MAC.

The first part of AUTN is calculated by an “exclusive or” (XOR) connection of the Sequence Number SQN and the Anonymity Key AK. AK = f5(K,RAND); f5 is a key generating function or f5 = 0. AK is used to conceal SQN as the latter may expose the identity and location of the user. The concealment of SQN is to protect against passive attacks only. If no concealment is needed then f5 = 0 (AK = 0).

The second part of AUTN is the Authentication and key Management Field AMF. AMF is part of the user’s database in the AuC. Operator-dependent, different f1..f5 algorithm may be defined. AMF may be used to indicate the algorithm and key used to generate a particular authentication vector.

The third part of AUTN is the Message Authentication Code MAC. MAC = f1(K,SQN,RAND,AMF); f1 is a message authentication function.

21



AV Generation

AuC

AV =

RAND GeneratorDatabase

(IMSI;K)

AMFAuthentication &key Management

Field

SQN Generator

SQNSequence Number

RANDRandom Number

Ksecret Key

f1 f2 f3 f4 f5

MACMessage Authentication

Code

� Network Authentication


� UserAuthentication

CKCipher Key

� Ciphering

IKIntegrity Key

� Ciphering

AKAnonymity Key

� SQN Anonymity

RANDRandom number


CKCipher Key

IKIntegrity Key

AUTNAuthentication Token

SQN � AK48 bit

AMF16 bit

MAC64 bit

AMF� selection of f

1-5 version

� different f1-5versions possible

(operator-dependent)

Fig. 14

22


Authentication in the USIM

With the “Authentication Request” message, the authentication parameter RAND and AUTN are transmitted from the VLR/SGSN to the USIM. The purpose of this procedure is to authenticate user & network and to establish a new pair of cipher and integrity keys CK & IK between the VLR/SGSN and the USIM.

Upon receipt of RAND and AUTN the USIM first computes the Anonymity Key AK = f5(K,RAND) and retrieves the Sequence Number SQN. SQN = (SQN XOR AK) XOR AK.

Second, the USIM calculates the Expected Message Authentication Code XMAC. XMAC = f1(K,SQN,RAND,AMF). For network authentication, XMAC is compared with MAC (included in AUTN). If they are different, the USIM sends back the “Authentication Reject” message to the VLR/SGSN and abandons the connection set-up. “Authentication Reject” includes an indication of the cause for the rejection. In the case of “Authentication Reject”, the VLR/SGSN shall initiate an Authentication Failure Report procedure towards the HLR.

If the network authentication is all right, the USIM verifies that the received SQN is in the correct range.

If the USIM considers SQN to be not in the correct range, it sends “Synchronization Failure” back to the VLR/SGSN including the appropriate parameter, and abandons the connection set-up.

If SQN is in the correct range, the USIM computes RES. RES = f2(K,RAND).

Furthermore, the USIM calculates the Cipher Key CK = f3(K,RAND) and the Integrity Key IK = f4(K,RAND). CK and IK are stored in the USIM for the following ciphering of user data and integrity check of signaling data.

Finally, RES is included in the “Authentication Response” message and sends back from the USIM to the VLR/SGSN. The VLR/SGSN needs the RES for User Authentication. If RES = XRES from the selected AV, the authentication of the user has been successful. If they are different, the VLR/SGSN shall initiate an Authentication Failure Report procedure towards the HLR.

23



Authentication in the USIM

USIMVLR / SGSN(stores AV(1..n))


[RAND(i), AUTN(i)]

Authentication Response

[RES(i)] Compare:

� XRES(i) = RES(i) ?� �� User Authentication

Generate:

� RES� XMAC� CK

� IK

RAND SQN � AK AMF MAC AUTNK

f5 AK

f1f2f3f4

��

SQN

IK CK RES XMAC

CipheringIntegrityCheck

to network�� User

Authentication

XMAC = MAC ?�� Network

Authentication

XMAC:

Expected Message

Authentication Code

AK: Anonymity Key

AMF:Authentication &key ManagementField

or Authentication Reject

[XMAC �� MAC]

Fig. 15

24


Synchronization Failure

At the beginning of the Authentication process, the AuC generates the Sequence Number SQN. SQN shall have a length of 48 bit. The structure & content of SQN is operator-dependent. SQN may contain information used to restrict the Authentication Vector AV validity time or to verify the Serving Network SN Identity.

SQN, being a part of AUTN, is transmitted via VLR/SGSN (“Authentication Data Response”) to the USIM (“Authentication Request”).

The USIM regenerates SQN and verifies that the received SQN is in the correct range.

If the USIM considers SQN to be not in the correct range, it sends the “Synchronization Failure” message back to the VLR/SGSN including the appropriate parameter, and abandons the connection set-up.

Upon receiving a “Synchronization Failure” message from the UE, the VLR/SGSN sends an “Authentication Data Request” with a Synchronization Failure Indication to the AuC of the user’s Home Environment HE together with RAND and the appropriate parameter received from the UE.

The AuC checks the parameter, generates a fresh set of AVs and sends them with an “Authentication Data Response” message to the VLR/SGSN.

Whenever the VLR/SGSN receives a new set of AVs from the AuC in an “Authentication Data Response” to an “Authentication Data Request” with Synchronization Failure Indication it deletes the old AVs for that UE. The VLR/SGSN may now start a new authentication process to the UE based on a new AV from the AuC.

25



SQN Synchronisation Failure

USIM

HLR

AuC

VLR / SGSN

Network

Authentication

Data Request [IMSI]

Authentication Data

Response [AV(1..n)]

generates SQN:• length = 48 bit• content operator-dependent e.g. for restricted AV validity time, verification of SN Id.

• SQN � AK � AUTN

• Re-generates SQN

• SQN in correct range ? No � Synchronisation Failure Yes � continue Authentication


[RAND(i), AUTN(i)]

or Authentication Response

[RES(i)]

Synchronisation Failure

Auth. D

ata R

equest

[Syn

chro

n. Failu

re In

dicatio

n]

& Auth

. Data

Response

[AV(1

..n)]

Fig. 16

26


5 Ciphering & Integrity Check


UE

SNServingNetwork

S-RNCVLR /SGSN

HEHome

Environment

HLR

AuC

Cipheringprevents eavesdropping

of user data / signalling

Data Integrity Checkprovides security against

unauthorised modification of

• signalling data /

• change of data origin

AV Request:Providing Keysfor Ciphering &Integrity Check

Key

Setting

Ciphering & Integrity Check

Mandatory!!Mandatory!!

Fig. 17

27


Ciphering & Integrity Check

To start the security features Ciphering (optional) & Integrity Check (mandatory), three steps are necessary:

Connection Establishment

At the connection start the RRC Connection Establishment also informs the network about the UEs security capabilities. They include the MEs UMTS Encryption Algorithms UEAs and UMTS Integrity Algorithms UIAs. In Rel. ’99 only 2 UEAs and 1 UIA are defined (TS 33.102): UEA0 = “no encryption”, UEA1 = Kasumi encryption, UIA1 = Kasumi algorithm. The S-RNC stores the UEs security capabilities.

Authentication & Key Generation in UE

Authentication & key setting may be initiated by the network as often as the network operator wishes. Key setting can occur as soon as the identity of the mobile subscriber, i.e. (P-)TMSI or IMSI, is known by the VLR/SGSN.

The security parameter RAND is transmitted with the "Authentication Request" message from the VLR / SGSN to the UE. The USIM uses RAND to generate the Cipher Key CK for ciphering and the Integrity Key IK for integrity check. Now CK & IK are available in the USIM and in the VLR/SGSN.

Security Mode Set-Up

Sending the "Security Mode Command" to the S-RNC, the VLR/SGSN initiate integrity & ciphering. This command includes the IK & CK to be used.

The S-RNC decides which UEA & UIA will be used, taking into account the UEs security capabilities. If the requirements in the “Security Mode Command” cannot be fulfilled, the S-RNC sends a “Security Mode Reject” message to the VLR/SGSN.

Next, the S-RNC starts the DL integrity protection. It is mandatory to start integrity protection of signaling messages at each new signaling connection establishment between the UE and the VLR/SGSN (exceptions listed in TS 33.102).

The S-RNC sends the “Security Mode Command” to the UE. This message includes the selected UIA and also UEA, if ciphering shall be started. Furthermore, parameter for integrity check, an indication on the core domain (CS/PS) and optionally the time of cipher start are included.

The UE verifies the received “Security Mode Command” message (Integrity Check) and starts UL integrity protection.

Finally, the UE sends “Security Mode Complete” to the S-RNC. The security mode set-up is terminated with the “Security Mode Complete" message, which is send from the S-RNC to the VLR/SGSN. This message includes the selected UIA & UEA.

28



Connection Establishmentincludes: UE security capabilities (UIAs / UEAs)

S-RNCUE

VLRSGSN*1 also denoted by f9

*2 also denoted by f8

Authentication Request[RAND, AUTN]

Authentication Request[RAND, AUTN]

Authentication Response[RES]

Authentication Response[RES]

generates:RES, XMAC,

CK, IK

Authentication& Key

Generation

stores UIAs, UEAs

UMTS Integrity Algorithm UIA*1:• UIA1 = Kasumi algorithm

UMTS Encryption Algorithm UEA*2 :• UEA0 = no encryption• UEA1 = Kasumi encryption

further UIA/UEA planed

UMTS Integrity Algorithm UIA*1:• UIA1 = Kasumi algorithm

UMTS Encryption Algorithm UEA*2 :• UEA0 = no encryption• UEA1 = Kasumi encryption

further UIA/UEA planed

Security Mode Command [UIA, UEA*, CN domain,

Integrity Parameter, Cipher Start]

Security Mode Complete

Security Mode Command [ IK, CK, UIAs, UEAs]

Security Mode Complete

SecurityMode

Set-Up• Select UIA & UEA• start Integrity

startIntegrity

start (De-)Ciphering

Connection Set-up:Key Setting & Security Mode Set-Up

•••

•••

start (De-)Ciphering

Fig. 18

29


Data Integrity Check: Basic Principle

The Data Integrity Check is used between the UE and the VLR/SGSN to protect signaling data against unauthorized modification and change of data origin.

It is mandatory to start integrity protection at each new signaling connection establishment between the UE and the VLR/SGSN. Exceptions (e.g. emergency call) are listed in TS 33.102.

Integrity protection starts after the “Security Mode Command”. The messages “Security Mode Command”, “Security Mode Complete” and all following messages are integrity protected.

The principle of the Integrity Check is the following:

The signaling data to be protected and the Integrity Key IK are used in the transmitter (UE or S-RNC) as input for the UMTS Integrity Algorithm UIA. The result of this calculation is a kind of a check sum of this data. This check sum is appended to the signaling data to be transmitted.

Signaling data and appended check sum are send from transmitter (UE or S-RNC) to receiver (S-RNC or UE).

In the receiver, the signaling data and the IK (stored in the receiver) are again used as input for the same UIA. The newly generated check sum (expected check sum) is compared to the transmitted check sum.

If during transmission signaling data are modified or someone tries to simulate the users signaling, the expected check sum and the transmitted check sum differ and the non-authorized modification becomes visible.

Receiver

Control Data

Transmitter

S-RNCUE

* exceptions listed in TS33.102 (6.5.1)

provides security against:

• unauthorised modification of control data

• change of data origin

Control Data: � start of Integrity protection mandatory � nearly all control data Integrity protected*

Control DataEncrypted

check sumControl Data

Encrypted

check sum

IK dependent

check sum generator IK

check sum

generator

Expected

check sum

Encrypted

check sum

IK

Data Integrity CheckBasic Principle

Equal?

*not in case ofemergency calls

Fig. 19

30



Data Integrity Check – UMTS Integrity Algorithm UIA

The UMTS Integrity Algorithm UIA (different types of UIA can be used; currently only UIA1 using a Kasumi algorithm is defined; see TS 33.102/6.5.6) is often also denoted as f9.

The transmitter (UE or S-RNC) uses the Control Data and the integrity parameter Integrity Key IK, Integrity Sequence Number COUNT-I, a random value generated by the network side FRESH and the direction bit DIRECTION as input for f9.

Based on these input parameters the transmitter computes the Message Authentication Code for data Integrity MAC-I (i.e. the check sum):

MAC-I = f9(Control Data,IK,COUNT-I,FRESH,DIRECTION).

The MAC-I is appended to the control data and transmitted over the radio link.

The receiver computes the Expected Message Authentication Code for data Integrity XMAC-I in the same way as the transmitter computed MAC-I. The data integrity of the control data is checked by comparing XMAC-I with the received MAC-I.

Remarks to the integrity parameter:

Integrity Key IK: There may be one IK for CS connections IK(CS) and one for PS connections IK(PS). The data integrity of radio bearers for user data is not protected.

FRESH: There is only one FRESH parameter value per user. The input parameter FRESH protects the network against replay of signaling messages by the UE. At connection set-up the S-RNC generates a random value FRESH and sends it to the UE in the RRC “Security Mode Command” message. The value FRESH is subsequently used by the UE and S-RNC throughout the duration of a single connection. This mechanism assures the network that the user is not replaying any old MAC-Is.

COUNT-I: the integrity sequence number COUNT-I is composed on basis of the RRC sequence number RRC SN and the RRC Hyperframe Number RRC HFN.

DIRECTION: the direction identifier bit indicates UL or DL direction (DIRECTION = 0 for UL and 1 for DL).

31



Receiver(UE or S-RNC)

Data Integrity CheckUMTS Integrity Algorithm UIA

Transmitter(UE or S-RNC)

f9 (UIA)f9 (UIA)

IKIntegrity Key

COUNT-I

Directiondirection bit

FRESH

Control Data

RRC: Security Mode Command[UIA, UEA, CN domain, Cipher Start,

FRESH, MAC-I]

RRC: Security Mode Complete[MAC-I]

• verify MAC-I• start Integrity - ...

UE

S-RNC

• Select UIA & UEA• start Integrity - compute MAC-I, - generate FRESH

MAC-I

• random value • S-RNC generated• valid for connection duration• prevents replaying of old MAC-Is

UL = 0DL = 1Integrity

Sequence No.

encryptedcheck sum

Control DataMAC-I

IKIntegrity Key

COUNT-I

Directiondirection bit

FRESH

Equal?

XMAC-I

(X)MAC-I: (Expected) Message Authentication Code for Integrity

Fig. 20

32


Ciphering – UMTS Encryption Algorithm UEA

Similar to GSM, UMTS performs encryption of user data and signaling to prevent eavesdropping on the radio interface.

For CS and PS data encryption is performed between the S-RNC and the UE.

Like in GSM the “plain text” is ciphered in the transmitter connecting it via XOR operation with a cipher sequence (UMTS: Keystream Block). The ciphered text block is transmitted via radio interface. In the receiver the plain text is recovered connecting the ciphered text block via XOR operation with the cipher sequence / Keystream Block.

The algorithm producing the Keystream Block is the UMTS Encryption Algorithm UEA. UEA is often denoted as f8. Different UEA implementations are possible. Currently only UEA0 (no ciphering) and UEA1 (Kasumi encryption) are available.

The UMTS keystream block is generated in the UE and S-RNC feeding the cipher parameter Cipher Key CK, Ciphering Sequence Number COUNT-C, bearer identity BEARER, transmission direction DIRECTION and the length of the keystream LENGTH into f8.

Keystream Block = f8(CK,COUNT-C,BEARER,DIRECTION,LENGTH).

Remarks on the cipher parameter:

Cipher Key CK: There may be one CK for CS connections CK(CS) and one for PS connections CK(PS).

COUNT-C: The ciphering sequence number COUNT-C is generated by MAC or RLC frame and sequence information.

BEARER: the radio bearer identifier BEARER is input to avoid that for different keystream an identical set of input parameter values is used.

DIRECTION: the direction identifier bit indicates UL or DL direction (DIRECTION = 0 for UL and 1 for DL).

LENGTH: The length indicator LENGTH indicates the length of the required keystream block. LENGTH shall affect only the length of the Keystream block, not the actual bits in it.

33



UE or S-RNC

CipheringUMTS Encryption Algorithm UEA

S-RNC

UE

f8 (UEA)CKCipher Key

COUNT-C Bearerradio bearer id.

Lengthlength indicator

Keystream block

UL = 0DL = 1

CipherSequence No.

indicate lengthof required

keystream blockDirectiondirection bit

CKPS

& CKCS

1 Bearer parameter /user radio bearer

Keystream block��Plain text block = ciphered text block

ciphered text block Plain text blockKeystream block�� =

“cipher sequence”

not in case ofemergency calls

Fig. 21

34


UMTS Security Features: Summary

The UMTS system provides some mechanism to guarantee the network access security. Some features are still the same as in GSM, others have been enhanced, and two new aspects have been additionally defined. The following network access security features have been defined in Rel. ’99:

IMEI Check:

To prevent the usage of stolen or not allowed mobile equipment, the mobile equipment identification can be checked by the network. This feature remains the same as in GSM.

P-TMSI / TMSI Allocation:

To guarantee the user identity confidentiality respectively the user location confidentiality the permanent user identity IMSI is normally not transmitted over the radio interface. The user is normally identified by the temporary identity TMSI / P-TMSI, by which he is known in the serving network. This feature remains the same as in GSM.

Authentication:

In UMTS authentication is extended compared to GSM. Additionally to the User Authentication a Network Authentication is introduced.

User Authentication is the property that the Serving Network SN checks the real identity of the user, preventing non-authorized access to the network.

Network Authentication is a check whether the connected SN is really authorized by the user’s Home PLMN to provide him services. This includes the guarantee that this authorization is recent.

Ciphering

Ciphering prevents eavesdropping of user data and signaling over the radio interface. UMTS ciphering has been enhanced compared to GSM/GPRS.

Data Integrity Check

The Data Integrity Check has been introduced as a new security feature in UMTS. It provides security against unauthorized modification of signaling data respectively the change of data origin.

35



UE VLRSGSN


Summary

TMSI / P-TMSI Allocation- allocated by VLR / SGSN instead of IMSI

- protects user identity & location confidentiality

Authentication

- User Authentication: network checks real user identity;

prevents misuse / misappropriation

of network resources / services

- Network Authentication: UE checks network authorisation

to provide service

IMEI Checkprevents usage of

stolen / not allowed ME

Cipheringprevents eavesdropping of

user data / signalling on Uu

Data Integrity Checkprovides security against unauthorised

modification of signalling data /

change of data origin

S-RNC

Fig. 22

36

Chapter 5

UTRA Aspects

UTRA Aspects Siemens

Contents

1 Power Control 23

2 RAKE Receiver 181

3 Handover 1217

4 Exercise 2027

5 Solution 2433

UTRA Aspects

1


1 Power Control

Power Control

UTRA Aspects

Frequency f

Time t

Power

P

1

2

3Power

Control

Fig. 1

2

Siemens UTRA Aspects

Power control principle

Fast power control is essential in CDMA systems. Since many subscribers transmit in the same frequency band and as the same frequency can be used in principle in each cell (re-use = 1), each user can cause interference for the others. The power control is used to limit interferences. The capacity of the CDMA system is mainly limited by the level of the (inter- and intra-cell) interferences. As a result, an optimized power control greatly optimizes the system capacity.

UL power control reduces the interference between different UE, DL power control the interference between neighboring base stations, BTS.

The power control is also used to solve the so-called "near-far" problem. For different UE with identical transmission power, the power received at the BTS of UE located near the BTS is more powerful than the power of the more remote UE. This may mean that only the information of the UE near to the BTS can be interpreted. This must be prevented as much as possible. In ideal cases, the power received at the BTS is identical for all UE served by the BTS (assuming the transfer rates are identical). This ideal situation also represents the maximum capacity of the cell.

Genuine fast power control is necessary because of the mobility of the UE. This mobility causes rapid variation in the attenuation of the power of the UE. Let us consider an example: the power of UE received at the BTS can increase by several factors in milliseconds because the UE, for example, has moved away from the "radio shadow" of a building and has a direct line of sight to the BTS. The interference of the UE can then disrupt the communication between the BTS and all other UE – the situation must be governed by a fast power control.

CDMA:

everyone

in the same

frequency band

�

„everyone is

interferer

for everyone“

BTS

BTS

Power Control

Principle

„near far“problem:

P(UE1) �� P(UE2)

at BTS-Receiver

P(UE1)

P(UE2)

UE1

UE2

UL & DL

Power Control for

Interference limitation

Fig. 2

3

UTRA Aspects Siemen


UTRA – Power control types

Three different power control types are used in UTRA for efficient power control: Open Loop Power Control, Inner Loop Power Control and Outer Loop Power Control.

Open Loop Power Control

Open Loop Power Control is used for UL transmissions to control the initial transmission power (e.g., for random access) of UE. The attenuation of the transmission power of the BTS is analyzed by the UE as part of the control. The original power of the BTS is radiated together with other system parameters as broadcast information. The UE power is initially controlled on the basis of the analyzed attenuation.

This initial control can only be coarse because the UL and DL attenuations (for FDD) can differ.

Inner Loop Power Control

For Inner Loop Power Control the BTS or UE compare the quality of the received signals with a specified value. This value describes the ratio of the (wanted) received signal power (the signal) and the (unwanted) interference from other sources (the noise) called the signal-to-noise ratio (S/N) or (S/N)def.

In the FDD mode, the Inner Loop Power Control is also referred to as a Closed Loop Power Control because of the different frequencies used for UL and DL.

If the analyzed S/N value is better than the defined value, (S/N)def, the BTS or UE transmit a command to the corresponding opposite side to reduce transmission power. If the S/N is poorer, an increase in transmission power is ordered. The commands are covered by the term Transmit Power Control (TPC). Values for TPC are "Up" and "Down".

In the TDD mode, the BTS and UE independently control the power for themselves according to the completed S/N measurements and specified values (S/N)def because of the different frequencies used for UL and DL.

Outer Loop Power Control

The specification of the (S/N)def values used in the Inner Power Control is made by the Serving RNC (SRNC). The SRNC has access to estimates of the actual transmission quality using measurement reports for Node B's and UE. The quality can vary due to modified transmission conditions (e.g., UE speed). To assure transmission quality, the SRNC must be able to vary the (S/N)def values.

4

UTRA Aspects Siemen


S/N > (S/N)def

� TPC = Downelse TPC = Up DL:

Inner Loop PCP(BTS) � UE TPC

UL:

• Inner Loop PC

P(UE) � BTS TPC

• Open Loop PC

P(UE) � oriented at

BTS DL Power;

for initial transmission

UTRA

Power ControlPC - Types:

• Open Loop PC

• Inner Loop PC

• Outer Loop PC

BTS(Node B)

PC: Power Control

TPC: Transmit Power Control

S/N: Signal to Noise

UE: TS 25.101/102 (FDD/TDD)BTS: TS 25.104/105 (FDD/TDD)

PC-types: TS 25.401


PC-types: TS 25.401

UERNC

Outer Loop PC:(C/I)

defvariation, to

guarantee QoS (BER,..)

Fig. 3

5


UTRA power control – Parameters

The UTRA FDD and TDD modes have different power control cycles and maximum power stages of the UE.

Power control cycles

The UTRA FDD mode uses 1500 PC cycles/s for the Inner Loop Power Control. Each timeslot (TS) has a Transmit Power Control (TPC) command.

The UTRA TDD mode flexibly uses 100 to 800 PC cycles/s for the Inner Loop Power. The minimum number of 100 PC cycles/s is correlated with the duration of a frame (10 ms). Depending on the frame configuration, up to 800 PC cycles may be required for a subscriber.

Power classes and dynamic performance

The maximum power of the Node B (FDD & TDD) is vendor-specific. Dynamic performance of 30 dB must be ensured. The power can be provided in PC stages of 1, 2 or 3 dB.

The UE has 4 power classes that differ in the FDD and TDD modes.

In the FDD mode, the maximum power of the UE classes is 2000 mW, 500 mW, 250 mW and 125 mW.

In the TDD mode, the maximum power of the UE classes is 1000 mW, 250 mW, 125 mW and 10 mW. The 10 mW class is used for unlicensed operation.

The minimum UE power should be about 0.04 µW. The power can be provided in PC stages of 1, 2 or 3 dB.

3G TS 25.410 provides an overview of the different PC types. Power classes and dynamic performance are described in TS 25.101 or 25.102 for UE (FDD or TDD), in TS 25.104 or 25.105 for Node B (FDD or TDD).

6

UTRA Aspects Siemen


• FDD: 1500 PC cycles/s (1 TPC je TS)

• TDD: 100 - 800 cycles/s(100/s: per frame; >100/s:depends on frame configuration)

• FDD: 1500 PC cycles/s (1 TPC je TS)

• TDD: 100 - 800 cycles/s(100/s: per frame; >100/s:depends on frame configuration)

UEmax. power (4 classes):

• FDD: 2000 / 500 / 250 / 125 mW

• TDD: 1000 / 250 / 125 / 10* mW

PC steps: 1, 2, 3 dB

min. power: 0,04 �W

Receiver Sensitivity: -110 dBm

UTRA

Power Control



BTSmax. power:vendor specific

PC steps:1, 2, 3 dB

Dynamic:30 dB (= 1000)

�� UTRA CapacityInterference limited

�� system stability

TPC: Transmit Power Control

* for unlicensed operation

Fast

Power Control

Fig. 4

7


2 RAKE Receiver

RAKE Receiver

UTRA Aspects

Path 1

Path 2

Path 3

RAKE Receiver

��

CDMA Advantagefrom

Multipathpropagation

Fig. 5

8


RAKE receiver

CDMA can benefit from multipath propagation of radio waves with the use of a so-called RAKE receiver. The information for transmission reaches the receiver in practice not only by direct "line of sight", but also via echos from obstacles. Normally this increases the noise level, a situation that is not desirable. The reflected information passes over longer paths than the direct line of sight and is therefore delayed. If the delay is longer than one chip, the receiver usually regards the reflected information as undesirable noise. The use of RAKE receivers turns this disadvantage to an advantage.

A RAKE receiver has a number of RAKE fingers. Each of these RAKE fingers changes (by de-spreading) broadband signals with different delays from the same source (i.e., with the same spreading code) back into user information by using the spreading code. This can be done because the different RAKE fingers apply the spreading code with delays.

The RAKE fingers obtain information from a so-called Matched Filter (MF) for the synchronization required. The MF compares incoming information with predefined data sequences. These sequences are shifted in time. If the incoming chip sequences match the predefined sequences, a power peak is registered. Predefined information and information in the UL / DL contain so-called pilot sequences or the mid-ambles of the TDD bursts. The MF returns information on the delays of the different user signals in this way. It also supplies information on the amplitude of the different user signals.

The RAKE fingers are responsible for the de-spreading of the user signals received by multipath propagation. The fingers also correct the information with regard to phase and adapt the timing of the information.

Depending on the signal strength (MF information), the information components are summed (Maximum Ratio Combining).

A strong signal consisting of multipath components is therefore obtained in this way with a RAKE receiver.

9

UTRA Aspects Siemen


RAKE

Receiver

Path 1

(d1,a1)

Path 2 (d2, a2)

Path 3 (d3, a3)

d: delaya: attenuation

RAKE Receiver:

several „finger“ for multipath components

De-Spreading

Code (t-d1) „Finger 1“

De-Spreading


De-Spreading


��

a1

a2

a3

Maximum

Ratio

Combining

RAKE finger:

• Despreading (� MF-Info!)

• Phase correction

• „Delay“ correction

Matched Filter MF:

measures „Pilot“

� „Delay“ estimation

Fig. 6

10


MultiUser Detection (MUD)

MultiUser Detection (MUD) and Interference Cancellation (IC) can be used for clearing intra-cell noise. In doing so, the MUD / IC can

1. increase the capacity of the system. Different models indicate that MUD / IC can theoretically increase the system capacity by a factor of 2.8 and

2. reduce the "near-far" problem. The broadband information of all UE in a cell generated with the use of different spreading codes is received by the receiver of a BTS (Node B). The information is despread in the receiver using the same spreading code. MUD processes the signals jointly in order to separate undesirable interference due to the other users in the cell from the signal wanted. In this way, large parts of the intra-cell interference can be separated from the overall signal and canceled: hence Interference Cancellation (IC). The desired signal of a specific user is clearly distinguishable from the background. MUD therefore provides a much better signal to noise ratio (S/N). Since the capacity of CDMA systems is mainly limited by interference (there is however also a restriction regarding the number of available orthogonal codes), MUD / IC contributes to an increase in capacity. MUD / IC is a relatively complex method. It is consequently mainly to recommend for applications in the UL direction – i.e., in Node B. However, there are also studies on the use of MUD / IC in user equipment (UE). The interferences of the most powerful "disturbers" can be canceled at least.

MultiUser

Detection MUD

BTS

(Node B)

UE 1:

Code 1

UE 2:

Code 2

UE n:

Code n

Node B

De-Spreading

Code 1

De-Spreading

Code 2

De-Spreading

Code n

Mu

ltiU

ser D

ete

cti

on

MU

D &

Inte

rfe

ren

ce C

an

cell

ati

on

IC

Data 1

Data 2

Data n

MUD:

• mainly for UL (in Node B)

• reduces Intra-Cell interferences � increases capacity• reduces Near-Far problem

Fig. 7

11

UTRA Aspects Siemen


3 Handover

Handover

UTRA Aspects

Measurement:

Connection quality & strength

+ strength of own & surrounding BTS

UE

Measurement:

Connection quality & strength

BTS

Measurement Report

RNC

HOV

Decision

Pre-processing of measurements

Activation of new BTS

„Active Set“ Update

MeasurementReport

UMTS Handover

• decision similar GSM

• initiated by RNC

• performed by UE

Fig. 8

12


UTRA handover

The criteria and procedures for performing handover in UMTS are similar to those in GSM. The UE and BTS determine the quality and strength of a radio transmission. The UE also determines the signal strength and quality of its own and the local BTS's. The measurement values are compiled in a measurement report for use by the RNC as a basis for deciding for or against handover. If handover is decided upon, the new BTS is activated and included in the so-called active set. The RNC is responsible for decisions regarding the acceptance or rejection of handovers, while the execution (initiation of contact with the new BTS) is the responsibility of the UE.

Hard handover

Hard handovers refer to handovers in which a mobile station (MS) transmits its user information only via one base station at any one time. Up until the time of the handover command, the MS communicates with the old base station over a specific physical channel. After the handover command, the MS changes the physical channel and then communicates with the new base station.

Hard handovers are used in GSM and in the following cases in UMTS:

During TDD / TDD handovers

During FDD handovers if the frequency (interfrequency handover) or the Core Network is changed

During inter-system handovers – for example, when changing from FDD to TDD or from UMTS to GSM.

Soft handover

Soft handovers refer to handovers in which a mobile station (MS) transmits its user information via more than one base station at the same time. Soft handovers can be used in CDMA systems in order to prevent an increase in power of the MS in boundary areas between different cells. This reduces the interference level and therefore increases the capacity of the system. Moreover, the contact with more than one base station ensures the connection to a moving MS in difficult terrain.

Soft handovers are used in IS-95 and MC-CDMA and in the following cases in UMTS:

During FDD / FDD handovers (without frequency changes).

13

UTRA Aspects Siemen


Hard Handover

UL

DL

ULDL DL

Soft Handover

Hard & Soft Handover

• GSM

• UTRA TDD

• UTRA FDD at:• Interfrequency HoV (HCS)• CN-Change

• Inter-System HoV• FDD - TDD• UMTS - GSM

• IS-95

• MC-CDMA

• UTRA FDD

Fig. 9

14


Soft handover

UE can communicate with two or three BTS's during soft handovers in the UTRA FDD mode due to the fact that all cells use the same frequency. If the mobile station enters the boundary area between two or three cells, the RNC can decide that a connection with two or three BTS's is advantageous. The RNC reserves corresponding codes in the different cells for the UE and commands the UE to implement handover to the new BTS (or BTS's). As of this time, the information is handled by the relevant BTS's. The identity of the cells involved in the connection is stored in the RNC as an active set.

The Node B's receive the transmission from the UE, despread it and forward the information over the Iub interface to the RNC. The RNC combines this information and forwards it via the Iu interface to the Core Network (CN). This procedure is implemented frame for frame. The quality of the supplied frames is the basis for assessment. Only information in frames with top quality is used.

The gain due to reception of additional signals in soft handovers is also known as macro diversity.

In the opposite direction, the RNC splits the information from the Core Network and forwards it to the different Node B's. During soft handover the UE receives the transmission of the (apart from the TPC command) identical information from the various Node B's / BTS's. The transmission information from the BTS's is despread by different RAKE fingers and combined (Maximum Ratio Combining – MRC).

Softer handover

Softer handovers are handovers between sector cells in the same Node B. The transmission information received via the antennae of the different sector cells is handled by different RAKE receivers and combined in the Node B itself (Maximum Ratio Combining – MRC). Softer handovers are internal Node B affairs. Additional (Iub) transmission capacity to the RNC is not required.

The gain due to reception of additional signals in softer handovers is also known as macro diversity.

15

UTRA Aspects Siemen


Sector cells

Soft / Softer Handover

Node B

Node B

RNC

Node B

CN

Combining /Splitting

ActiveSet

Node B

Soft Handover Softer Handover

RNC

• between sector cells

• Combining via RAKE

• Node B internal

Iu

Iub

Iub

Iub

Active Set:max. 3 Cells

Fig. 10

16


Inter-RNC Soft Handover

An interesting special case of soft handover is the inter-RNC handover. In this case, the Node B's involved in the soft handover belong to different RNC's.

The RNC responsible for control of the soft handover is referred to as the serving RNC (SRNC). It combines information received from the different Node B's in the direction of the Core Network (CN) or splits the information transmitted in the opposite direction. It also stores information regarding the cells involved in the soft handover (in an active set).

The other RNC responsible only for allocating radio resources is known as the drift RNC (D-RNC).

Since the handover is to be controlled autonomously in UMTS by the UTRAN as part of the Radio Resource Management (RRM), an interface is required between both of the RNC's participating in the soft handover. D-RNC and S-RNC exchange signaling information and user information via the Iur interface.

The S-RNC has no anchor functionality (comparable to an anchor MSC). The D-RNC can adopt the function of the S-RNC with an S-RNC relocation procedure if necessary. The previous S-RNC is then released. The link between both RNC's over the Iur interface is no longer required. The link is directly handled by the participating Node B (or Node B's) via the Iub interface using the new S-RNC and sent from there to the CN via the Iu interface.

Soft Handover

Node B

Node B

RNC

Node B

CN

Combining /Splitting

ActiveSet

Inter-RNC HoV

Iu

IubIub

Iub

RNC

Iur

• S-RNC: Combining/Splitting + RR allocation

• D-RNC: only RR allocation

• change D-RNC �� S-RNC possible

S-RNC: Serving RNCD-RNC: Drift RNC

RR: Radio Resource

Fig. 11

17

UTRA Aspects Siemen


UTRA FDD & TDD – Key parameters

The UTRA FDD and TDD modes have many common key parameters:

��Bandwidth B = 5 MHz

��Chip rate Rc = 3.84 Mchip/s

��Re-use factor = 1

��The timing structures are identical:

��1 TS = 2560 chips (=2/3 ms)

��1 frame = 15 TS = 10 ms (= 38400 chips)

��1 superframe = 72 frames = 720 ms (= 6 GSM TCH multiframes)

��FDD and TDD both use the "OVSF code tree" for channelization codes.

Differences between TDD and FDD are mainly based on the different multiplex methods used (and of course on the different UL/DL coordination/frequencies).

The FDD mode uses pure DS-CDMA thereby producing a continuous transmission. The shortest transmission duration is one frame (10 ms).

The TDD mode uses a TDMA / DS-CDMA hybrid solution which produces transmission of bursts.

The FDD mode uses 1500 power control cycles (1 TPC / TS).

The TDD mode uses 100 to 800 power control cycles/s depending on the frame configuration.

The FDD mode mainly uses soft handovers (except for changes in frequency / system).

The TDD mode uses hard handovers.

The FDD mode has advantages in its use of relatively large cells (macro and micro cells), particularly for UE moving at high speed. The TDD mode offers advantages for small-space, quasi-stationary applications (in pico and micro cells).

The main advantages of the TDD mode are as follows:

��Flexible use in new frequency areas (reframing); only 1 x 5 MHz required

��Unlicensed operation with low power equipment (power class 4) possible

��Asymmetric distribution of resources for UL & DL (higher resource efficiency).

18

UTRA Aspects Siemen


Zone 3: Suburban

Zone 2: Urban

Zone 1:

Indoor

Macro Cell Pico CellMicro Cell

UTRA FDD & TDD

Key Parameter

FDD• continuous transmission

• SF = 4 - 256/512

• 1500 PC-cycles/s

• Soft Handover

TDD• bursty structure

• SF = 1 - 16

• 100 - 800 PC cycles/s

• Hard Handover

FDD & TDD• bandwidth B = 5 MHz

• chip rate Rc = 3,84 Mchip/s

• Re-Use = 1

• OVSF Code tree

• 1 TS = 2/3 ms = 2560 chip

• 1 frame = 10 ms• 1 Superframe = 72 frames

Fig. 12

19

Chapter 6

UMTS Radio Access

Basic Principles

UMTS Radio Access: Basic Principles Siemens

Contents

1 Transmission Principles & Examples 23

2 Principle of CDMA & Example 191

3 UTRA: The UMTS Terrestrial Radio Access 2127

3.1 UTRA Conception & Harmonization 2228

3.2 FDD / TDD – Technical Parameters 2632

3.3 UTRA Codes 3036

3.4 UTRA Timing Structures 3440

3.5 Summary – Key UTRA Parameters 3642

4 MC-CDMA / UTRA / TD-SCDMA Comparison 3845

5 Exercise 4251

6 Solution 4657

UMTS Radio Access: Basic Principles

1


1 Transmission Principles & Examples

FDD TDD

UL DL

Duplex

transmission

Multiple

Access

FDMA

TDMA CDMA


& 2G Examples

UTRA Basics

Fig. 1

2

Siemens UMTS Radio Access: Basic Principles

Transmission principles and examples

The mobile transfer of information in a cell between base stations and mobile stations requires coordination of the information transmission. Two different aspects require coordination. Firstly, during today's typical full duplex transmission, the two transmission directions (uplink and downlink) must be coordinated between a mobile station and the base station. Two different principles are applied for duplex transmissions: Time Division Duplex (TDD) and Frequency Division Duplex (FDD). Secondly, the transmission between the different mobile stations of a cell and the base station must be coordinated. Three different multiplex methods are mainly used for this purpose: Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA).

Duplex transmission: FDD & TDD

Two duplex methods are used for coordinating the uplink (UL) and downlink (DL) components of a transmission between a base station and a mobile station, namely Frequency Division Duplex (FDD) and Time Division Duplex (TDD).

UL and DL are implemented for FDD in different frequency bands. The gap between the two frequency bands for UL and DL is known as the duplex distance. It is constant for all mobile stations in a standard. Generally the DL frequency band is positioned at the higher frequency than the UL band.

In the case of TDD, UL and DL are implemented in the same frequency band. This is done by dividing the band into timeslots (TS) and frames. A frame contains a specific number, n, of timeslots, TS. A number of these n timeslots is reserved for UL transmission (half of the timeslots in 2G systems) and the remaining for DL transmission. The duration of a frame determines the cyclical repetition of the corresponding UL / DL transmission. The UL and DL transmission occurs quasi simultaneously – i.e., the duration of a frame is generally in the range of a number of ms.

TDD transmission is mainly used as of the 2nd mobile communications generation (in digital transmissions). Digital transmission simplifies speech and data compression. As a result, only a fraction of the time needed for analog transmission is required for digital transmission of subscriber data.

UMTS Radio Access: Basic Principles Siemen

3


DL

FDD: UL / DLseparated by

Frequency!

TDD:

UL / DLseparated by

Time!

Duplex Transmission:

FDD & TDD

FDD: Frequency Division Duplex

TDD: Time Division Duplex

TS: Time Slot

frequency f

Tim

e t

duplex distance

frequency f

Tim

e t

UL

��

UL

DL

UL

DL

UL

Frame

with n TS

Fig. 2

4


Multiplex methods

Multiplex methods are used to divide the limited frequency resources of a cell between the different subscribers and mobile stations in the cell. Three different methods are mainly used today: Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA) and Code Division Multiple Access (CDMA). Other multiplex methods are currently being researched or developed (for example, Space Division Multiple Access – SDMA).

Frequency Division Multiple Access (FDMA)

FDMA divides the available frequency range into channels with a specific bandwidth (frequency band). One of these frequency bands is made available to a single subscriber without restriction throughout the entire duration of a connection. Each subscriber in a cell therefore uses a different frequency band than the other subscribers. In this way undesirable noise can be avoided (or reduced as much as possible or as required).

Time Division Multiple Access (TDMA)

Unlike FDMA, a single frequency band is available to a number of different subscribers with TDMA. The frequency band is divided into TDMA frames for this purpose. Each frame is divided into n timeslots (TS). Each of the n timeslots of a frame can be assigned to a different subscriber. In this way, a single frequency band can carry up to n subscribers. The transmission of a single subscriber comprises individual timeslots assigned cyclically to the subscriber (generally 1 TS per frame; longer cycles are also possible). With TDMA, each frequency band is also used only by a single subscriber at a particular time. This prevents interference occurring between different subscribers (or prevents noise as much as possible or as required).

Code Division Multiple Access (CDMA)

In contrast to TDMA and FDMA, multiple subscribers can use the same frequency band at the same time with CDMA. Each subscriber is provided with a unique (in the cell) code for this purpose. The transmitter links the original information with the code. The coded information is then transmitted over the radio interface. The original information is regenerated in the receiver using the same code.


5


frequency f

time t

Power

P

TS 1

TS 2

TS 3

TDMA

frequency f

time t

Power

P

1 2 3

FDMA

frequency f

time tPower

P

1

2

3

CDMA

Multiple

Access

BS & MS with common

knowledge according

FDMA

TDMA

CDMA

Frequency

Time

Code

Multiple Access

co-ordination of

restricted frequency resources

to different subscriber

Fig. 3

6


Duplex & multiplex methods – Examples

FDD / FDMA

Systems belonging to the 1st mobile communications generation (1G) generally use FDD methods for duplex transmission and FDMA for multiplex access. Subscriber UL and DL are in different frequency ranges. One frequency band in the frequency ranges is available without restrictions to individual subscribers in each case. Examples of cellular FDD / FDMA systems are the 1G systems – AMPS, NMT, TACS and C450.

The C450 system, for example, uses the frequency ranges 450 – 455.74 MHz and 460 – 465.74 MHz for UL and DL transmissions respectively. The frequency bandwidth is 20 kHz, the duplex distance 10 MHz.

FDD / TDMA

Systems belonging to the 2nd mobile communications generation (2G) generally use FDD for duplex transmission and TDMA for multiplex access. Subscriber UL and DL are therefore in different frequency ranges. Usually one timeslot (TS) is cyclically available to individual subscribers in a frequency band in the frequency ranges. To enable faster data rates, multiple TS's of a frequency band can be grouped together for a subscriber in some cases. Examples of FDD / TDMA systems are the cellular 2G systems – GSM, D-AMPS and PDC.

GSM900, for example, uses the frequency ranges 890 – 915 MHz and 935 – 960 MHz for UL and DL transmissions respectively. The frequency bandwidth is 200 kHz and the duplex distance 45 MHz. The frequency bands are divided into TDMA frames, each 4.615 ms in duration. Each TDMA frame is divided into 8 TS's.

TDD / TDMA

Low-range 2G systems sometimes use TDD for duplex transmission and TDMA for multiplex access. An example of TDD / TDMA transmission is DECT.

DECT uses 10 frequency bands, each with a bandwidth of 1.728 MHz, in the frequency range 1880 – 1900 MHz. The frequency bands are divided into TDMA frames, each 10 ms in duration. Each TDMA frame is divided into 24 TS's. 12 TS's in a frame are used for UL transmission, 12 for DL.

FDD / CDMA

CDMA is used by a number of 2G systems, but mainly by 3G systems. An example of a 2G system that uses FDD for duplex transmission and CDMA for multiplex transmission is the IS-95 system (described later).


7


1G: FDD,

pure

FDMA

e.g.

C450,

NMT,

AMPS

Example:C450

frequency [MHz]

Duplex distance:10 MHz20 kHz

450 455,74 460 465,74

UL DL

••• •••

time

Examples

2Gcellular: FDD, TDMA

(&FDMA)

e.g.

GSM, PDC,

D-AMPS

frame

4.615ms

time

TS4

TS5

TS6

TS7

TS0

TS1

TS2

TS3

frequency [MHz]

••• •••

Duplex distance: 45 MHz

200 kHz

Example:GSM900

1,728

MHz

DL

UL

TD

MA

fra

me

(1

0 m

s)

12

34

56

78

9101112131415161718192021222324

1 2 3 4 5 6 7 8 9 10

20

MHz

1,88GHz

AA

1,90GHz

2G CT: TDD, TDMA e.g. DECT

Example:DECT

time

frequency

[MHz]

2G Example CDMA:

IS-95 (later)

Fig. 4

8


2 Principle of CDMA & Example

CDMA

Basics & Example

frequency f

time t

Power

P

1

2

3

Code Division

Multiple Access

UTRA Basics

Fig. 5

9


The CDMA principle

CDMA is a Spread Spectrum Technology (SST). The origins of SST go back to the 1920's. SST's were used from the 1950's to the 1980's in the military sector – for example, for satellite navigation. CDMA has been released as an SST for civilian use since the mid-1980's. The first cellular mobile communications system to use CDMA for multiplex transmission was IS-95. It began commercial operation at the end of 1995.

In SST's a narrowband signal with high information concentration is transformed to a broadband signal with low information concentration – this is known as spreading. The signals are very stable against the influence of narrowband natural or technical interference (background noise) and interfering transmitters (intentional jamming). There are different ways of performing the spreading.

For spreading subscriber information for CDMA, a unique (in the cell) code is provided for each subscriber. This code is referred to as the spreading code. The linkage of the high bit rate code with the original subscriber information transforms the original signal into a broadband signal. This broadband signal is transmitted together with broadband signals from other subscribers using the same frequency band over the radio interface. The receiver receives the sum of all of these signals. By relinking the summation signal with the (synchronized) subscriber code the original subscriber information is regenerated (a process known as de-spreading). The remaining information stays in its broadband form and therefore constitutes an underlying signal. The information remains useful as long as the underlying signal does not dominate the despread signal. The information for the different subscribers can be separated because of the orthogonal (or quasi orthogonal) attributes of the code used.

CDMA

Principle

Po

we

r P

frequency f

Unspread

Signals

Spread

Signals

Radio Transmission =

� spread signals

after

De-Spreading

user 1

user 2

user 1 & 2CDMA:• Spread Spectrum Technology• every user with unique Code

• high bit rate Code: Spreading / De-Spreading

frequency f

Fig. 6


10


Advantages of CDMA

The CDMA principle is associated with many attributes that can have positive effects for transmission of information.

The coded transmission and the low information concentration of the CDMA signals were particularly important for the military applications. A transmitted signal can only be despreaded, and the data regenerated, if the receiver has the correct spreading code. The low information concentration allows information to be discretely transmitted – the signals are for all intents and purposes concealed in background noise.

The high level of stability of the broadband information transmission against the effects of narrowband background noise is vitally important for military and civil utilization. Frequency hopping is used in narrowband systems (such as GSM) to obtain this effect.

Yet another CDMA attribute is extremely important for civil applications in mobile communications systems. CDMA in principle allows the re-use of the same frequency band in all neighboring cells (re-use = 1). In contrast, the same frequency bands cannot be re-used in neighboring cells in FDMA or TDMA systems. To prevent interference by subscribers at the same frequencies or in the same timeslots, cells with identical frequencies must be spatially separated. In FDMA and TDMA systems, cells are arranged in a careful, complicated frequency planning process. Re-use schemes of 1/7, 1/9, etc. are typical. As a result, only one part (1/7, 1/9, ...) of the theoretically available frequency band can be used in the one cell.

CDMA can therefore in principle do without complicated frequency planning, and allows efficient usage of the available (scarce) frequency resources.

The limits to transmission capacities in FDMA and TDMA systems are determined by a fixed number of physical channels. With CDMA, however, there is a "soft" capacity limit. The capacity of CDMA systems is mainly restricted by the interference of other subscribers in a cell (so-called intra-cell interference) and interference from other cells (inter-cell interference).

Another CDMA advantage is a stable transmission especially in severe environment. This is caused by the so-called Multipath Advantage and Soft Handover. Both effects are described later.

Due to an essential need for precise and fast Power Control, CDMA mobile stations also need less transmission power than TDMA mobiles. The UMTS Power Control is also described later on.


11


CDMA

Advantages

1/7

5/7

6/7

7/7

2/7 4/7

3/7

2/7Re-UseDistance

Frequency & radio network planning

1/1

1/1

1/1

1/1

1/1 1/1

1/1

TDMA(e.g. GSM with Reuse 1/7)

CDMA(UMTS; Reuse: 1)

• Stability�� narrow-band interference• Stability in severe environment (� Multipath Advantage, Soft HoV)• simple frequency planning (Re-Use: 1)

• efficient radio resource usage

• lower transmission power (� Power Control)

Fig. 7

12


CDMA types

Signals can be spread for CDMA using a number of different methods. The following three CDMA methods are most commonly used: TH-CDMA, FH-CDMA and DS-CDMA.

Time Hopping CDMA (TH-CDMA)

The information-carrying signal is not continuously transmitted in the TH-CDMA method. Instead, information is transferred in bursts. The burst transmission time is specified by the spreading code.

TH-CDMA was developed at the end of the 1940's as the first CDMA method, and was used for military purposes.

Frequency Hopping CDMA (FH-CDMA)

The carrier frequency of the information-carrying signal is changed constantly during FH-CDMA. Very fast as well as slow changes are possible. The bandwidth at any particular time is relatively narrow. When considered over a longer period, FH-CDMA is just as much a broadband method as TH-CDMA and DS-CDMA. The change in carrier frequency is specified by the spreading code.

An example of the civil use of FH-CDMA is the so-called Bluetooth standard. Bluetooth allows the transmission of information at high data rates over small distances in the unlicensed frequency range around 2.4 GHz.

Direct Sequence CDMA (DS-CDMA)

In DS-CDMA, subscriber information (digital in 2G and 3G systems) is spread directly by linking with a sequence of the spreading code. This results in continuous (in contrast to TH-CDMA) transmission of the broadband signal over the entire bandwidth (in contrast to FH-CDMA).

DS-CDMA is used for IS-95 and the Globalstart satellite system, for example. In 3G, UMTS is based on DS-CDMA.


13


CDMA

Types

tim

e t

frequency f

Direct

Sequence

(DS-CDMA)

Frequency

Hopping

(FH-CDMA)

Time

Hopping

(TH-CDMA)

DS-CDMA� IS-95

� Globalstar

�� UMTS

FH-CDMA

� Bluetooth

Fig. 8

14


Direct Sequence CDMA – Transmission and reception

Digital, binary subscriber information is linked in the transmitter with the spreading code generated by a code generator – this process is termed spreading. The spreading code consists of a high bit rate code sequence. The smallest unit of information in the spreading code is referred to as a chip to distinguish it from the smallest unit of subscriber information, the bit. The rate of the spreading code is known as the chip rate. The information obtained by spreading is modulated to a carrier frequency. The higher the information rate (i.e. the chip rate), the wider the bandwidth of the resulting signal.

The broadband signal is transmitted over the radio interface.

The receiver demodulates the signal and links the resulting information with the same spreading code used in the transmitter. This process is known as de-spreading. De-spreading produces the original subscriber information. It is vital for de-spreading that the code in the receiver be exactly synchronized in time with the code in the transmitter. A shift by just one chip prevents information from being regenerated.

DS-CDMA:Transmission /

Reception

Spreading

CodeGenerator

WidebandModulation

CarrierGenerator

De-Spreading

CodeGenerator

De-Modulation

CarrierGenerator

BinaryData

RB

Air

Interface

RB

BinaryData

RC

time-synchronisation

!!!

RB: Bit Rate

RC: Chip Rate

fT: Carrier frequency

RC

fT

1

Chip

Spreading

Code

+1

-1

Fig. 9


15


Spreading / de-spreading

In UMTS, the binary, digital subscriber data (1, 0) is converted on the transmission side to bipolar data (+1, –1) before the spreading process takes place. The spreading code also consists of bipolar data. The value of a chip can be +1 or –1. The subscriber data is then multiplied by the high chip rate spreading code. The result is the coded data, which is then transmitted over the radio interface.

The receiver multiplies the received, code data sequence with the bipolar spreading code to obtain a bipolar data sequence. The original subscriber data is recovered by converting this data sequence to binary, digital data.

Spreading Factor (SF)

The spreading factor (SF – also frequently known as the Processing Gain, Gp) indicates the number of chips that spread a symbol each time (see below). The SF therefore states the relationship between the chip rate, Rc (chip/s) and the data rate of the subscriber (symbol/s or bit/s). SF also gives the relationship between the spread bandwidth B and unspread bandwidth W.

Information units: chips, bits, symbols

The smallest unit of digital information is generally called a bit (an abbreviation derived from "binary digit"). To distinguish the smallest units in the original subscriber information, spreading code and data transmitted over the radio interface, different terms are used, namely: bit, chip and symbol respectively.

A symbol can have different numbers of bits depending on the modulation method used for transmission over the radio interface. Symbols have one bit each in the Gaussian Minimum Shift Keying (GMSK) method used in GSM and in the Binary Phase Shift Keying (BPSK) method used for UMTS UL (FDD only) transmission. In the Quadrature Phase Shift Keying (QPSK) method used generally for UMTS, a symbol has two bits, and in the 8 Phase Shift Keying (8PSK) methods used in EDGE even three bits.


16


Spreading / De-Spreading

1 0 1 0Binary Data

Bipolar

Data

Spreading

Code

Spreaded

Data

+1

+1

+1

-1

-1

-1

+1

+1

-1

-1

Spreading

Code

Bipolar

Data

1 0 1 0Binary Data

1 Symbol

1 Chip

Bit / Symbol ��modulation principlee.g.: GMSK: 1 / 1 (Bit/Symbol)BPSK: 1 / 1QPSK: 2 / 18PSK: 3 / 1

x

=

x

=

SF = Rc

/ RS

= B / W

B = bandwidth, spreaded

W = bandwidth, un-spreaded

RS: Symbol Rate [symb/s]

RB: Bit Rate [bit/s]

RC: Chip Rate [chip/s]

SF = Spreading Factor

GMSK: Gaussian Minimum Shift Keying

BPSK: Binary Phase Shift Keying

QPSK: Quadrature PSK

8PSK: Eight PSK

Fig. 10

17


Spreading / de-spreading – An example

The example portrays CDMA transmission for two users. Orthogonal spreading codes with a spreading factor of 2 are used for both users (1/2).

The original information of the two users (data users 1 and 2) are converted to bipolar data (1 / 2) and multiplied by the spreading code (1 / 2).

The coded signals interfere with each other during transfer over the radio interface.

The receivers receive the overall signal (of both users). By multiplying the overall signals with the spreading code (1 / 2) different data sequences (de-spread data 1 / 2) are obtained for users 1 and 2. The sequences are integrated during the duration of a symbol. The information is interpreted as 1 for positive results and 0 for negative results. The final result is the original information of the two users 1 / 2.

Integration / capacity restrictions

The integration of the data signals is an important component of the de-spreading process. If a single coded signal of a user is multiplied by the correct code and then integrated during the length of a symbol, information is obtained that can be clearly interpreted. The higher the spreading factor, the clearer ("stronger") the information. A high spreading factor therefore assures a high level of transmission security (but at a lower data rate however).

If the coded signal of a user is multiplied by a different code and then integrated, a zero is obtained for strict orthogonality of the codes – i.e., the result cannot be interpreted. With the quasi orthogonality used in practice there is little "misinformation" when compared with the process of multiplying with the correct code followed by integration. Care must be taken in practical applications to prevent the sum of the "misinformation" from outweighing the strong (correct) information – i.e., the system capacity is limited by the background noise from the transmissions of other users.


18


Receiver: � Spreaded Data; hier: �� = 0 -2 -2 0 2 0

1 0 1Data User 1

Bipolar

Data 1

Code 1

Spread

Data 1

+1

+1

+1

-1

-1

-1

x

=

0 0 1Data User 2

Bipolar

Data 2

Code 2

Spread

Data 2

+1

+1

+1

-1

-1

-1

x

=

�� Signals

(Receiver)

Code 1

De-Spread

Data 1

+2

+1

+2

-2

-1

-2

x

=

0

0

after

Integration

+2

-2

�� User Data 1 1 0 1

�� Signals

(Receiver)

Code 2

De-Spread

Data 2

+2

+1

+2

-2

-1

-2

x

=

0

0

after

Integration

+2

-2

�� User Data 2 0 0 1

Spreading /

De-Spreading

Code 1

= ( 1 / -1)

Code 2

= ( 1 / 1)

Example:

SF = 2;

2 user

Fig. 11

19


2G CDMA example: IS-95

IS-95 was developed at the end of the 1980's/beginning of the 1990's and released in 1993 as the TIA standard (USA) for the 800-MHz range. The standard was revised in 1995 (IS-95A). The system was taken into commercial operation at the end of 1995. Other TIA and ANSI standards are available as IS-95 variants for the 1900-MHz range and for transmissions at higher data rates (up to 115.2 kbit/s).

MC-CDMA, one of the 3G systems evolving from IS-95, is based on IS-95 parameters.

IS-95 uses FDD for duplex transmission. The duplex distance in the 800-MHz range is 45 MHz and 80 MHz in the 1900-MHz range.

IS-95 uses CDMA for multiplex access. The bandwidth B is 1.25 MHz. In practice, 3 carriers can be accommodated in 5 MHz of bandwidth under consideration of guard bands.

The network is synchronized to within a few µs using GPS signals.

The chip rate, Rc, used for IS-95 is 1.2288 Mchip/s. Orthogonal Walsh codes are used as spreading codes. The spreading factor is 64. The spread information is overlaid with so-called pseudo noise codes specific for the BTS and MS (the chip rate is also 1.2288 Mchip/s). These pseudo noise codes have quasi orthogonal attributes.

QPSK is used for modulation in DL transmissions and BPSK in UL transmissions.

Fast Power Control is required for IS-95 CDMA. 800 power control cycles are carried out per second.

IS-95 parameter:

FDD / CDMA

B = 1,25 MHzRc = 1,2288 Mchip/sSF = 64Modulation: QPSK / BPSK (DL / UL)Power Control: 800 cycles/s

time t

1.25 MHz

Po

we

r P

64 PN-Codes

frequency f

Duplex distance:45 / 80 MHz at800/1900 MHzrange (USA)

Example CDMA:

IS-95 (2G)

Fig. 12


20


3 UTRA: The UMTS Terrestrial Radio Access

Zone 4: Global

MSS

Zone 3: Suburban

Zone 2: Urban

Zone 1: Indoor

Macro-cell Pico-cellMicro-cell

FDD TDD

UTRA:

UMTS Terrestrial Radio Access

UTRA Basics

Fig. 13

21


3.1 UTRA Conception & Harmonization

UTRA was technically conceived in different phases.

1st phase of the UTRA conception: Studies on UTRA

In the 1st phase proposals for multiplex methods were collected by the ETSI SMG2 and analyzed with regard to their possibilities and common features. The 1st phase ended with the SMG#23 Plenary Session in 06/1997.

2nd phase of the UTRA conception: Concept evaluation

Based on the results of the 1st phase, 5 concepts were selected and named after the first five letters in the Greek alphabet. Concept groups were assigned the task of evaluating the different concepts. In addition, the SMG2 specified the general requirements for UTRA in more detail in the 2nd phase. The phase ended with the SMG#24 Plenary Session held in 12/1997. The 5 concepts were supported by different groups with different interests (vendors, operators, regulatory bodies, etc.).

The �-concept (orthogonal FDMA: narrowband FDMA/TDMA allowing combination of

different carriers) and the �-concept (broadband TDMA with 1.6 MHz bandwidth and an option for TS combination) were withdrawn even before this plenary session. It

was decided to adopt the �-concept (Opportunity Driven Multiple Access) as an optional solution for subsequent supplementation of UTRA. ODMA supports packet data transfer between the originating and destination locations via a network of intermediate relay nodes.

The �-concept (pure CDMA with Rc = 4.096 Mchip/s) and �-concept (TDMA/CDMA with a bandwidth of 1.6 MHz, Rc = 2.167 Mchip/s and GSM timing structure) presented themselves at the SMG#24 session as UTRA solutions. In the SMG#24A Plenary Session held on January 28 and 29, 1998, it was decided to use both concepts for UTRA.


22


��-concept

��-concept

��-concept

��-concept

��-concept

��-concept

��-concept

��-concept

��-concept

��-concept

PrinciplePrinciple Supported bySupported by

W-CDMAW-CDMAEricsson, Nokia, NEC, Panasonic, Fujitsu, Mitsubishi

Ericsson, Nokia, NEC, Panasonic, Fujitsu, Mitsubishi

OFDMAOFDMA Sony, Telia, Lucent, Bosch

Sony, Telia, Lucent, Bosch

W-TDMAW-TDMA Philips, Nokia, France Telecom

Philips, Nokia, France Telecom

TD-

CDMA

TD-

CDMA

UMTS-Alliance: Siemens, Bosch, Alcatel, T-Mobil, Motorola, Nortel, Italtel

UMTS-Alliance: Siemens, Bosch, Alcatel, T-Mobil, Motorola, Nortel, Italtel

ODMAODMA Vodaphone, Swiss Telecom

Vodaphone, Swiss Telecom

RemarksRemarks

pure CDMAFDD; 4.096 Mchip/s;

4,4 - 5,2 MHz

pure CDMAFDD; 4.096 Mchip/s;

4,4 - 5,2 MHz

TDMA/FDMATDMA/FDMA

TDMATDMA

TDMA & CDMA FDD/TDD

2.267 Mchip/s; 1,6 MHz;

TS / Frame wie GSM

TDMA & CDMA FDD/TDD

2.267 Mchip/s; 1,6 MHz;

TS / Frame wie GSM

option for

�� and ��

option for

�� and ��

Phase 1:

UTRA studies

(1996 - 06/97)

Phase 2:

Evaluation

(06 - 12/97)

Selection of

5 concepts:

�� - ��

Selection of

�� & ��- Concept

(01/98)

UTRA Conception

(ETSI)

Fig. 14

23


3rd phase of the UTRA conception: Harmonization

It was decided during the SMG#24A Plenary Session to use the �-concept for the

paired bands in UMTS – i.e., as UTRA FDD mode. The �-concept was to be used for the UMTS unpaired bands – i.e., as UTRA TDD mode. Both modes were harmonized with each other by 06/1998 with the consequence that dual mode operation (FDD/TDD) presents no problems. Both modes were designed in such a way that handover to GSM is unproblematic. The bandwidth of both modes is 5 MHz, including the guard bands. 4.096 Mchip/s was selected as the Rc.

The modes were also harmonized in the 3rd phase with the IMT-2000 proposal from

ARIB (Japan), who supported the original �-concept as observers in ETSI.

The 3rd phase ended with the submission of the harmonized proposals by ETSI (UTRA FDD & TDD) and ARIB (WCDMA) to the ITU.

In the period following, the newly founded standardization project, the 3GPP, in which experts from ETSI (Europe), ARIB (Japan), TTA (South Korea), ANSI T1P1 (USA) and CWTS (China) participate, took over responsibility for completion of the UMTS Standard.

Harmonization of UTRA with cdma2000

The TIA (USA) proposal 'cdma2000' is intended as the 3G successors standard to IS-95. The technical parameters of cdma2000 and IS-95 are therefore very similar and ensure downward compatibility and handover between 2G IS-95 and 3G cdma2000. 3.6864 Mchip/s (for DL) and 1.2288 Mchip/s (for UL) were selected as the chip rates for cdma2000. In 06/1998 cdma2000 was also submitted as an IMT-2000 proposal to the ITU.

In the period following, major economic and patent law-related difficulties arose between the groups involved in IS-95 / cdma2000 and GSM / UMTS (WCDMA). For example, the different patents for CDMA and the 3G licensing in Europe and Asia were contentious points. The USA threatened to invoke the WTO (World Trade Organization) and block the work for approval of the IMT-2000 proposals in the ITU.

In order to put an end to the wrangling and to satisfy the requirements of an Operator Harmonization Group (OHG), the 3GPP accepted an OHG proposal in 07/1999 for harmonization of UTRA and cdma2000.

The result of the harmonization was as follows: UTRA TDD and FDD along with cdma2000 are given similar parameters to allow the development of chipsets for mobile stations for all three modes. The three modes are based on DS-CDMA and can be accommodated in 5 MHz of bandwidth. The signaling is harmonized. The following core differences still exist: UTRA can be used for non-synchronized networks, MC-CDMA for synchronized. UTRA TDD and FDD use 3.84 Mchip/s as chip rate; MC-CDMA n x 1.2288 Mchip/s.


24


UTRA conception

& harmonisationW-CDMA��-concept

TD/CDMA��-concept

TD/CDMA

TDD

UTRAFDD

UTRATDD

Phase 3:

harmonisation

(01 - 06/98)

Submission to ITU

(06/98)

ETSI-ARIBharmonisation

(05/98)

cdma2000

IMT-2000

harmonisation

UTRA - cdma 2000

(05 - 07/99)

UTRAFDD

UTRATDD

MC-CDMA(FDD)

4,096 Mchip/s 5 MHz

5 MHz 3,6864 Mchip/s

3,84 Mchip/s

Fig. 15

25


3.2 FDD / TDD – Technical Parameters

UTRA TDD / FDD – Common features

UTRA FDD and TDD modes were harmonized in many central areas – for example:

��Bandwidth B = 5 MHz (including guard bands)

��Chip rate Rc = 3.84 Mchip/s

��Modulation method: QPSK

��Re-use = 1 (i.e., same frequency possible in neighboring cells)

��Pulse shape

��Timing structure (frame & TS duration – described below)

��Spreading codes: based on OVSF (Orthogonal Variable Spreading Factor) codes

UTRA TDD / FDD – Differences

There are also differences in the following central aspects:

FDD uses pure WCDMA (DS-CDMA) for multiplexing. The information is transmitted continuously spread over the entire bandwidth. The shortest duration of a transmission is represented by a frame (10 ms).

TDD uses a hybrid solution of TDMA and WCDMA (DS-CDMA) as multiplex access. Like in GSM, the subscriber information is sent in the form of single bursts. A TDMA frame (10 ms) contains 15 timeslots (TS) that can contain bursts from different users (CDMA component).

FDD uses spreading factors of 256 to 4 (UL) or 512 to 4 (DL); TDD uses factors of 16 to 1.

FDD mostly uses soft handover and TDD hard handover (described later).

The 3G TS 25.201 provides an overview of the major common features and differences along with references to individual aspects.


26


time t

15

2

1

Frame

TS Po

we

r P

frequency f

time t

Po

we

r P

frequency f

TDDMode

UTRA conception

& harmonisation

FDD & TDD harmonised in:• bandwidth: 5 MHz

• chiprate: 3,84 Mchip/s

• modulation: QPSK

• Re-Use = 1

• pulse form

• time structure

• Spreading Codes (OVSF)

FDDMode

FDD

• pure WCDMA(continuous transmission)

• SF = 4 - 256 (DL - 512)• Handover: Soft

FDD & TDD differences:

TDD

• WCDMA & TDMA(Bursts: 15 TS / Frame)

• SF = 1 - 16• Handover: Hard

OVSF: Orthogonal Variable Spreading Factor Codes

UTRA L1 General Description:3G TS25.201

UTRA L1 General Description:3G TS25.201

Fig. 16

27


Variation in data rate

UMTS allows flexible, dynamic variation of the data rate. The data rate can be varied in different ways in the TDD and FDD modes.

In the FDD mode, the data rate can be varied by SF variation. SF can vary from 256 – 4 (UL) or from 512 – 4 (DL). This gives rise to symbol rates from 15 ksymb/s (UL) or 7.5 ksymb(s) (DL) to 960 ksymb/s. This data rate can include the simultaneous transmission of data belonging to different applications of the same subscriber. In other words, multimedia applications are possible.

The data rate can be varied in the TDD mode by SF variation and combination of timeslots (TS). SF can vary from 16 – 1, thus yielding symbol rates of 240 ksymb/s to 3.84 Msymb/s. These symbol rates must be regarded under consideration of the 15 timeslots, TS (TDMA component of the TDD mode). In this way, symbol rates from 16 ksymb/s to 256 ksymb/s are available to a subscriber using one TS by varying the SF from 16 to 1. This transmission rate can be increased by combining multiple timeslots in a TDMA frame for one user.

The data rate can also be increased in the TDD and FDD modes by allocating multiple codes to one user (if the UE is capable of doing so). The allocation of multiple codes is useful for different applications belonging to the same user that are served simultaneously. A fine level of granularity of the data rate can be obtained in this way.

Asymmetric allocation of frequency resources

Strongly asymmetric data streams in the UL and DL directions are expected, particularly with regard to the mobile use of the Internet in 3G. Both UTRA modes allow asymmetric transmission of subscriber data. The TDD mode enables network operators to respond in a flexible manner to the asymmetry and to optimize how they use their frequency resources. Different numbers of TS's can be used for UL and DL. However, at least two of the 15 TS's must remain reserved for UL or DL (for different TDD configuration options, refer to TS 25.221).


28


time t

Pow

er

P

15

2

1

frequency f

time t

Po

we

r P

frequency f

TDD

FDD

Data Rate

Variation

Asymmetric

UL/DL allocation !!

Example: UL DL

Data rate variation:

• SF = 1 - 16

• TS - combining

Data rate variation:

• SF = 4 - 256 (DL: 512)

(min. 2 TS for DL/UL)

SF =

Rc [chip/s] /

RS[symb/s]

flexibleSwitching Point

Fig. 17

29


3.3 UTRA Codes

The Spreading Code in UTRA is obtained multiplying two different code types: the Channelization Code and the Scrambling Code.

Channelization Codes

Channelization codes are used to separate channels from the same source.

For DL this channelization means the separation of different users (or, to take it a step further, different applications of different users) by the BTS.

For UL the channelization means the separation of different applications used simultaneously by the same UE. Up to 6 different applications are theoretically possible from individual UE.

The channelization codes for the TDD and FDD modes are Orthogonal Variable Spreading Factor (OVSF) codes and have orthogonal attributes.

Scrambling Codes

Scrambling codes are used to separate different sources.

For DL this means the separation of different BTS's. Each cell has a scrambling code to allow the UE to distinguish between neighboring cells. The scrambling codes are not globally unique cell codes.

For UL the scrambling means the separation of different items of UE in a cell. The scrambling codes are assigned to the UE by UTRAN.

FDD and TDD use different scrambling codes. So-called gold codes 10 ms in length (= 38400 chips) are used periodically in FDD. In TDD, sequences of 16 chips are used periodically.

TS 25.201 provide an overview of channelization and scrambling codes. Details on the channelization and scrambling codes used for FDD and TDD can be found in TS 25.213 and TS 25.223.


30


Channelisation Code

separates DL different UE

Channelisation Code

separates DL different UE

Channelisation Code separates

UL different applications

of 1 UE (max. 6; SF variable)

Channelisation Code separates

UL different applications

of 1 UE (max. 6; SF variable)

UTRA

Codes

Spreading & Modulation:TS 25.201 (UTRA Overview)TS 25.213 (FDD),

TS 25.223 (TDD)

Spreading & Modulation:TS 25.201 (UTRA Overview)TS 25.213 (FDD),TS 25.223 (TDD)

Spreading Code =

Channelisation Code

x Scrambling Code

(TS 25.201)

Channelization Code: separates physical channels

• DL: channels of the same BTS

• UL: channels of the same UE

Scrambling Code:separates sources

• DL: separates different BTS

• UL: separates different UE in 1 cell

Channelization Code: separates physical channels

• DL: channels of the same BTS

• UL: channels of the same UE

Scrambling Code:separates sources

• DL: separates different BTS

• UL: separates different UE in 1 cell

different BTS:Scrambling Codes

different BTS:

Scrambling Codes

BTS

BTS

BTS

different UE:Scrambling Codes

(RNC allocated)

different UE:Scrambling Codes

(RNC allocated)

Fig. 18

31


UTRA codes – Structure of channelization codes

The channelization codes in the FDD and TDD modes are used for the actual spreading process. The UTRA channelization codes are based on Orthogonal Variable Spreading Factor (OVSF) codes of different lengths. A symbol of user information is spread by a channelization code sequence with a specified length (= spreading factor, SF) – i.e., number of chips. Different data rates are obtained by using different spreading factors, SF.

Channelization codes are generated as shown in the next diagram. The (1x1) start matrix with the value "1" represents the channelization code with SF = 1. All other matrices are successively constructed by 4-fold insertion of the preceding matrix. Three of these matrices (top left and right, and bottom left) contain the original values of the preceding matrix while the fourth (bottom right) contains the inverted matrix value. The channelization codes of length n (SF = n) are obtained from the columns of the corresponding matrix (n x n).

A code tree arises in which all codes of a particular length (SF = 1, 2, 4, 8,..., 512) are orthogonal to each other.

If you take codes that are 256 long, there are 256 different orthogonal codes for 256 different users / applications for FDD DL, for example (ignoring the codes for signaling), with 15 ksymb/s. In contrast, there are only 4 orthogonal codes of length 4 (SF = 4) with which 960 ksymb/s can be obtained.

Note the following: codes of different lengths in the same branch of a code tree are not orthogonal. For this reason, codes of different lengths from the same branch are not permitted to be allocated. A code assigned from a branch of the code tree blocks all other codes of increasing or decreasing length on the same branch.


32


UTRA

Codes

CC1,0

= (1)

CC2,1

= (1,-1)

CC2,0

= (1,1)

CC4,0 = (1,1,1,1)

CC4,1 = (1,1,-1,-1)

CC4,2 = (1,-1,1,-1)

CC4,3 = (1,-1,-1,1)

CC256,0

CC256,1

CC256,2

CC256,255

CC256,254

•• •

• • •

SF = 1 SF = 2 SF = 4 SF = 256

Channelization Codes (CCn,m

) = OVSF Codes

• • •

CC1

= (1) CC2

= 1 11 -1

CCn

=CC

n/2CC

n/2

CCn/2

-CCn/2

CCn,m

generation:from columns in CC

n

Scrambling Codes:• FDD: for BTS / UE „Gold Codes“;

10 ms period (1 frame = 38400 chip)• TDD: for BTS / UE 16 Chip long,

pre-defined sequences

OVSF =

Orthogonal Variable

Spreading Factor

Fig. 19

33


3.4 UTRA Timing Structures

Chip

The shortest unit of time used in UTRA corresponds to the duration of a chip. Since a chip rate of 3.84 Mchip/s is used, the duration of a chip is about 260.4 pico seconds (ps).

Timeslot (TS)

A UTRA timeslot (TS) is defined as the length of 2560 chips: this corresponds to duration of 2/3 ms. A timeslot is the shortest repetitive period in UTRA.

A timeslot for the TDD mode means the time frame allowed by an HF burst.

In the FDD mode specific information is exchanged cyclically between the UE and network. An example of this is the power control information (Transmit Power Control – TPC).

Frame

A UTRA frame is defined by the duration of 10 ms. A frame therefore contains 15 timeslots.

In the TDD mode, a frame is identical with the TDMA frame – i.e., the cyclical repetitive pattern of the time slots.

In the FDD mode, a frame is the shortest possible transmission duration. Short data packets for setting up a connection, for transmission of SMS messages or packet-switched data packets are at least one frame in duration.

UTRA is a radio access solution allowing data rates that are not only flexible, but that can also be dynamically adapted. A frame is likewise (for TDD and FDD) the shortest period of time for changing the transmission rate.

Superframe

A UTRA superframe is defined as the duration of 72 frames – i.e., 720 ms.

A superframe is the counting period for defining physical channels. Since it exactly 6 times longer than a traffic channel (TCH) multiframe in GSM (= 120 ms), it enables adaptation of the timing patterns between UMTS and GSM – as is essential for inter-system handover between the two systems.


34


UTRA

time

structure

2560 chipsTime Slot

TS

2/3 ms

Frame f TS#0 TS#i TS#14••• •••

10 ms

f#1 f#i f#72••• •••Superframe

720 ms

1/3.840.000 s �� 260.4 nsChip

• shortest information unit in CDMA

• TDD: TS contains 1 Burst• FDD: cyclic repetition of control information (e.g. TPC)

• TDD: TDMA frame• FDD: shortest transmission duration• TDD & FDD: shortest pattern

� data rate adaptation

• TDD & FDD: Counting period for

� Def. Physical channels � Handover to GSM (GSM TCH Multiframe = 120 ms)

Fig. 20

35


3.5 Summary – Key UTRA Parameters

��Both UTRA modes (FDD and TDD) require a bandwidth B = 5 MHz.

��Both modes have the same chip rate: Rc = 3.84 Mchip/s.

��Both modes use a spreading code consisting of a channelization code and scrambling code for spreading user data.

��The spreading factors (SF) indicate the ratio between the user information (symbol) and the number of chips used for spreading the symbol.

��SF's from 1 – 16 are used in the TDD mode, SF's from 4 – 256 (UL) or 4 – 512 (DL) in the FDD mode for varying the data rates.

��The TDD and FDD use the same timing structures:

��a timeslot (TS) has 2560 chips and a duration of 2/3 ms

��a frame has 15 TS's and a duration of 10 ms

��a superframe has 72 frames and a duration of 720 ms.

The main difference between the UTRA FDD and MDD modes is in the multiplex methods used:

��The FDD mode uses pure DS-CDMA – i.e., broadband, continuous transmission (minimum transmission duration: 1 frame = 10 ms).

��The TDD mode uses a hybrid solution of TDMA and DS-CDMA – i.e., broadband but bursty transmission. The duration of a burst is one timeslot.


36


UTRA

Key Parameters

• bandwidth B = 5 MHz

• chiprate Rc = 3,84 Mchip/s

• SF = Rc / RS = 1 - 16 (TDD)4 - 256/512 (FDD)

Spreading Code =Channelisation Code x Scrambling Code

• 1 TS = 2/3 ms = 2560 chip

• 1 frame = 10 ms

• 1 Superframe = 72 frames

• TDD: bursty structure (TS)

• FDD: continuous transmission (� 10 ms)

Fig. 21

37


4 MC-CDMA / UTRA / TD-SCDMA Comparison

IMT-2000

UTRAFDD

UTRATDD

MC-CDMA(FDD)

MC-CDMA / UTRA / TD-SCDMA

Comparison

IS-95GSM

Downward compatible/

Handover possible

harmonisation

(chipsets possible for UTRA TDD, FDD & MC-CDMA mode)

UTRA Basics

Downward compatible/

Handover possible

Fig. 22

38


MC-CDMA / UTRA comparison

UMTS as the 3G successor standard to GSM and MC-CDMA as the 3G successor standard to IS-95 have been harmonized with each other as much as possible. The harmonization is intended to facilitate the development of chipsets for UE that can access these three major terrestrial IMT-2000 modes.

MC-CDMA is downward-compatible with IS-95 B. As in IS-95, the chip rate is 1.2288 Mchip/s and the carrier bandwidth is 1.25 MHz. However, n carriers (where n = 1, 3, 6, 9, 12) can be commonly used for a user connection in DL transmissions. The data is demultiplexed in this case on n carriers and can therefore be transmitted simultaneously.

In contrast for UL, the DS-CDMA principle is used with a carrier transmission rate of n x 1.2288 Mchip/s and a bandwidth of n x 1.25 MHz.

3 MC-CDMA carriers, including two guard bands, each 625 kHz wide, can be used in a 5-MHz frequency band. Frequency bands that until now were used for 2G systems can therefore be replaced in this way by MC-CDMA.

MC-CDMA uses the same modulation method as UTRA (QPSK).

Orthogonal Walsh codes of variable length (comparable to UTRA) are used as channelization codes for spreading.

The result is finally superimposed with a PN sequence to distinguish it from neighboring base stations. This PN sequence is identical to that used for IS-95. This also represents a reason for the compatibility between IS-95 and MC-CDMA. One sequence is sufficient to distinguish between the base stations in IS-95 and MC-CDMA since both systems (Global Positioning System – GPS) have synchronized networks. The offset of the PN sequence is used for clear distinction of the neighboring base stations.

In contrast to this, UTRA FDD and TDD networks are, like GSM networks, not synchronized. As a result, they are not dependent on other systems (e.g., GPS). Consequently, different scrambling codes are needed to distinguish between neighboring base stations.


39


Guard Band625 kHz

1 2 3 4 5 MHz

Carrier1,25 MHz 1,25 MHz 1,25 MHz

625 kHz DLn Carriern = 1, 2, 3,

6, 9, 12

ULn-fold

chip rate

Rc

=1,2288 Mchip/s

Rc

=1,2288 Mchip/s

Rc

=3,6864 Mchip/sR

c=

2,4576 Mchip/s

MC-CDMA

1 2 3 4 5 MHz

Carrier

UL&

DLRc

=3,84 Mchip/s

DS-CDMA: UTRA TDD & FDD

MC-CDMA / UTRA

Fig. 23

40


TD-SCDMA / LCR-TDD mode

From UMTS Release 4 on, a new RTT option, which has originally been developed by the Chinese SDO CATT, is included into the UMTS standard: Time Division - Synchronous CDMA. TD-SCDMA is included as a second TDD option with a lower chip rate. Therefore, it is called Low Chip Rate TDD mode (LCR-TDD).

The key characteristics of LCR-TDD are:

��Bandwidth: 1.6 MHz

��Chip Rate: 1.28 Mchip/s

��Spreading Factor: 1, 2, 4, 8, 16

��Radio Frame Length: 10 ms, subdivided into two 5 ms sub-frames

��Time Slot: 0.675 ms duration; 7 TS per sub-frame

��Data Rate Variation: SF-variation; TS combining; change of modulation; theoretically, a maximum of 2 Mbit/s can be supported

��Modulation: QPSK (Quadrature Phase Shift Keying) and 8PSK (8 Phase Shift Keying)

These key parameters are taken from UMTS R'4 TS 25.223.

1.6 MHzCarrier Bandwidth

1.28 MchpsChip Rate

1, 2, 4, 8, 16Spreading Factors

10 ms

(each sub-frame 5 ms)Radio Frame Length (divided into 2 sub-frames)

675 ��sTimeslots

supportedVariable Data Rates

QPSK & 8PSKModulation

TD-SCDMA

TD-SCDMA =

UMTS R`4Option

�LCR-TDDMode

R`4TS 25.223

R`4TS 25.223

Fig. 24


41

Appendix

Appendix Siemens

Contents

1 Appendix 1: References 23

2 Appendix 2: Abbreviations 45

Appendix

1

Appendix Siemens

1 Appendix 1: References

Books:

��V.K.G. Garg, K.F. Smolik, J.E. Wilkes, „Applications of CDMA in Wireless/Personal Communications“, Feher / Prentice Hall digital and wireless communications series (1997) ISBN 0-13-572157-1

��A.J. Viterbi: „CDMA: Principles of Spread Spectrum for third Generation Mobile Communication“ (1995), ISBN 0-201-63374-4

��T. Ojanperä, R. Prasad: „ Wideband CDMA for third Generation Mobile Communication“, (1998) ISBN 0-89006-735-X

��R. Prasad, W. Mohr, W. Konhäuser, „Third Generation Mobile Communications Systems, Artech House Publishers (2000) ISBN 1-58053-082-6

��H. Holma, A. Toskala, “WCDMA for UMTS”, John Wiley & Sons, Ltd. (2000); ISBN 0-471-72051-8

��T. Ojanperä, R. Prasad, "Wideband CDMA: Towards IP Mobility and Mobile Internet", Artech House Publishers (2001) ISBN 1-58053-180-6

��J. Korhonen: "Introduction to 3G Mobile Communications", Artech House Publishers (2001) ISBN 1-58053-287-X

��Heikki Kaaranen, Naghian Siamak, "UMTS Network: Architecture, Mobility and Services", Wiley, (2001) ISBN 0-47148-654-X

Magazines:

��Funkschau

��Gateway

��Mobilcom

��pcmobil

��Mobile Computer

��Amtsblatt der „Regulierungsbehörde für Telekommunikation und Post“

��SMG News (ETSI)

2

Siemens Appendix

3G Internet addresses:

��http://www.3gpp.org

��http://www.3gip.org

��http://www.itu.int/imt

��http://www.etsi.org

��http://www.umts-forum.org

��http://www.gsmworld.com

��http://www.cdg.org

3

Appendix Siemen

Appendix Siemens

2 Appendix 2: Abbreviations

Abbreviations used in this document or other documents according to the theme UMTS.

AAL ATM Adaptation Layer

AC Authentication Center

ACCH Associated Control CHannel

ACE Antenna Coupling Equipment

ADC Analog to Digital Converter

AGCH Access Grant Channel

AICH Acquisition Indication Channel

AMR Adaptive MultiRate speech

AMX ATM MultipleXer

AMPS Advanced Mobile Phone Services

ANSI American National Standards Institute (USA)

AP Application Part

ARFCN Absolute Radio Frequency Channel Number

ARIB Association of Radio Industries and Business (Japan)

ARQ Automatic Repeat reQuest

ASCI Advanced Speech Call Items


ATM Asynchronous Transfer Mode

AUC AUthentication Center

4

Siemens Appendix

BA BCCH Allocation

BCC Base transceiver station Color Code

BCCH Broadcast Control CHannel

BCH Broadcast CHannel

BER Bit Error Rate

BMC Broadcast / Multicast Control

BPSK Binary Phase Shift Keying

BS Base Station

BSC Base Station Controller

BSIC Base transceiver Station Identity Code

BSS Base Station System

BSSAP Base Station System Application Part

BSSMAP Base Station System Management Application Part

BTS Base Transceiver Station

5

Appendix Siemen

Appendix Siemens

CA Cell Allocation

CAMEL Customized Applications for Mobile network Enhanced Logic

CAP CAMEL Application Part

CATT China Academy of Telecommunication Technology (China)

CC Call Control

CC Country Code

CCCH Common Control Channel

CCH Control CHannel

CCITT Comité Consulatif International Téléphonique et Télégraphique

CCS7 Common Channel signaling System No. 7

CCU Channel Coding Unit

CDMA Code Division Multiple Access

CEPT Conference Europèene des Postes et Telecommunication

CGI Cell Global Identity

CI Cell Identity

CN Core Network

CP Call Processing

CPCH Common Packet Channel

CPICH Common Pilot Channel

CS Coding Scheme

CS Circuit Switched

CSCF Call State Control Function

CTCH Common Traffic Channel

CUG Closed User Group

6

Siemens Appendix

D-AMPS Digital AMPS

DCCH Dedicated Control Channel

DCH Dedicated Channel

DCS1800 Digital Cellular System in the 1800 MHz band

DECT Digital Enhanced Cordless Telephone

DL Down Link

DPCCH Dedicated Physical Control Channel

DPCH Dedicated Physical Channel

DPDCH Dedicated Physical Data Channel

DRNS Drift RNS

DRX Discontinuous Reception

DS-CDMA Direct Sequence CDMA

DSCH DL Shared Channel

DTAP Direct Transfer Application Part

DTCH Dedicated Traffic Channel

DTX Discontinuous Transmission

EFR Enhanced Full Rate speech

EIR Equipment Identification Register

ERC European Radiocommunication Committee

ERMES European Radio MEssage System

ESA European Space Agency

ETSI European Telecommunications Standard Institute

7

Appendix Siemen

Appendix Siemens

FAC Final Assembly Code

FACCH Fast Associated Control CHannel

FACH Forward Access Channel

FB Frequency correction Burst

FCCH Frequency Correction CHannel

FDD Frequency Division Duplex

FDMA Frequency Division Multiple Access

FEC Forward Error Correction

FN Frame Number

FPLMTS Future Public Land Mobile Telecommunication System (

FR Frame Relay

FR Full Rate speech

FRAMES Future RAdio wideband MultiplE access Systems

GEO GEostationary Orbital

GGSN Gateway GPRS Support Node

GMM Global Multimedia Mobility

GMPCS Global Mobile Personal Communication Systems

GMSC Gateway MSC

GMSK Gaussian Minimum Shift Keying

GP Guard Period

GPRS General Packet Radio Service

GPS Global Positioning System

GSM Global System for Mobile communications

GTP GPRS Tunneling Protocol

8

Siemens Appendix

HCR-CDMA High Chip Rate CDMA

HCS Hierarchical Cellular Structures

HEO High Elliptic Orbit

HLR Home Location Register

HO(V) HandOver

HPLMN Home PLMN

HSCSD High Speed Circuit Switched Data

HSS Home Subscriber Server

IAM Initial Address Message

ICO Intermediate Circular Orbits

ID IDentification

ID IDentity

IMEI International Mobile Equipment Identity

IMSI International Mobile Subscriber Identity

IMT-2000 International Mobile Telecommunications-2000

IN Intelligent Network

Inmarsat INternational MARitime SATellite


ITU International Telecommunication Union


IP Intelligent Peripheral

ISDN Integrated Services Digital Network

ISP Internet Service Provider

ISUP ISDN User Part

IWE InterWorking Equipment

IWF InterWorking Function

IWUP InterWorking User Part

9

Appendix Siemen

Appendix Siemens

JD Joint Detection

JDC Japanese Digital Cellular

Kc cipher Key

Ki individual subscriber authentication Key

LA Location Area

LAI Location Area Identity

LAN Local Area Network

LAPDm Link Access Protocol on the Dm channel

LCR-CDMA Low Chip Rate CDMA

LEO Low Earth Orbital

LES Land Earth Station

LIC Line Interface Circuit

LMT Local Maintenance Terminal

LR Location Register

10

Siemens Appendix

MAC Medium Access Control

MAP Mobile Application Part

MARISAT MARItime SATellite

MBS Mobile Broadband System

MCC Mobile Country Code

ME Mobile Equipment

MExE Mobile station application Execution Environment

MG Media Gateway

MGCF Media Gateway Control Function

MM Mobility Management

MMI Man Machine Interface

MML Man Machine Language

MNC Mobile Network Code

MOC Mobile Originating Call

MP Main Processor

MS Mobile Station

MSC Mobile services Switching Center

MSISDN Mobile Station international ISDN number

MSP Multiple Subscriber Profile

MSRN Mobile Station Roaming Number

MSS Mobile Satellite Systems

MT Mobile Termination


MTC Mobile Termination Call


MUX MUltipleXer

11

Appendix Siemen

Appendix Siemens

NB Normal Burst

NBAP Node B Application Part

NCC Network Color Code (PLMN color code)

NDC National Destination Code

NMT Nordic Mobile Telephone

NSS Network Switching Subsystem

O&M Operation and Maintenance

OACSU Off Air Call Set Up

ODMA Opportunity Driven Multiple Access

OFDMA Orthogonal Frequency Division Multiple Access

OMC Operation & Maintenance Center

OMC-B Operation & Maintenance Center for BSS

OMC-S Operation & Maintenance center for SSS

OSS Operation SubSystem

OVSF Orthogonal Variable Spreading Factor codes

12

Siemens Appendix

PA Power Amplifier

PACS Personal Access Communication System

PC Power Control

PCCH Paging Control Channel

P-CCPCH Primary Common Control Physical Channel

PCH Paging Channel

PCM Pulse Code Modulation

PCPCH Physical Common Packet Channel

PCU Packet Control Unit

PDA Personal Data Assistant

PDC Personal Digital Cellular (Japan)

PDCP Packet Data Convergence Protocol

PDN Packet Data Network

PDSCH Physical DL Shared Channel

PHS Personal Handy System (Japan)

PICH Page Indication Channel

PIN Personal Identification Number


PMR Private Mobile Radio

PP Point-to-Point

PRACH Physical Random Access Channel

PSTN Public Switched Telephone Network

QOS Quality Of Service

QPSK Quaternary Phase Shift Keying

13

Appendix Siemen

Appendix Siemens

RA Rate Adaptation

RACH Random Access CHannel

RANAP Radio Access Network Application Part

RAND RANDom number

REQ REQuest

RES RESponse

RF Radio Frequency

RFC Radio Frequency Channel

RFCH Radio Frequency CHannel

RFCN Radio Frequency Channel Number

RLC Radio Link Control

RNC Radio Network Controller

RNS Radio Network Subsystem

RNSAP Radio Network Subsystem Application Part

RRC Radio Resource Control

RRM Radio Resource Management

RSS Radio SubSystem

RX / Rx Receiver

14

Siemens Appendix

SACCH Slow Associated Control CHannel

SAP Service Access Point

SAPI Service Access Point Indicator

SB Synchronization Burst

SCCP Signaling Connection Control Part

S-CCPCH Secondary Common Control Channel

SCE Service Creation Environment

SCH Synchronization CHannel

SDCCH Stand- alone Dedicated Control CHannel

SF Spreading Factor)

SFH Slow Frequency Hopping

SGSN Service GPRS Support Node

SIM Subscriber Identity Module

SM Security Management

SMG Special Mobile Group

SMP Service Management Point

SMS Short Message Service

SN Subscriber Number

SN Switching Network

SP Signaling Point

SP Server Processor

SP Switching Point

SS Supplementary Services

SSF Service Switching Function

SSP Service Switching Point

STP Signaling Transfer Point

SW Software

15

Appendix Siemen

Appendix Siemens

T1 Standards Committee T1 Telecommunications

TA Terminal Adaptor

TAC Type Approval Code

TACS Total Access Communication System

TB Tail Bit

TCAP Transaction CApability Part

TCH Traffic CHannel

TCP Transmission Control Protocol

TD-CDMA Time Division CDMA

TDD Time Division Duplex

TDMA Time Division Multiple Access

TS-SCDMA Time Division Synchronous CDMA

TE Terminal Equipment

TETRA TErrestrial Trunked Radio Access

THSS Time-Hopping Spread Spectrum

TIA Telecommunication Industry Association

TMN Telecommunication Management Network

TMSI Temporary Mobile Subscriber Identity

TRAU Transcoding and Rate Adaptation Unit

TRX TRansceiver

TS Tele Service

TS TimeSlot

TTA Telecommunications TechnologyAssociation (South Korea)

TTC Telecommunication Technology Committee (Japan)

TX / Tx Transmitter

16

Siemens Appendix

UDP User Datagram Protocol

UE User Equipment

UL UpLink

UMTS Universal Mobile Telecommunications System

UP User Part

USIM UMTS Subscriber Identity Module

UTRA UMTS Terrestrial Radio Access

UTRAN UMTS Terrestrial Radio Access Network

UWC-136 Universal Wireless Communication

VAD Voice Activity Detection

VBR Variable Bit Rate

VBS Voice Broadcast Service

VHE Virtual Home Environment

VLR Visited (visitor) Location Register

VMSC Visited MSC

VoIP Voice over Internet Protocol

VPLMN Visited PLMN


WAP Wireless Application Protocol

WARC World Administrative Radio Conference

W-CDMA Wideband CDMA

WLL Wireless Local Loop

17

Appendix Siemen

Fast link dependent scheduling methods

Round Robin (RR)Cyclically assign the channel to users without taking channel conditions into accountSimple but poor performance

Proportional Fair (PF)Assign the channel to the user with the best relative channel qualityHigh throughput, fair

Max C/I RatioAssign the channel to the user with the best channel qualityHigh system throughput but not fair

Fast hybrid ARQ

Fast hybrid ARQ schemes

Chase combining : each retransmission is an identical copy of the original transmission.

Incremental Redundancy : each retransmission may add new redundancy

Fast link dependent scheduling

HSDPA channel structure

HSDPA channel structure

HS-DSCH - High-Speed Downlink Shared Channel:transport channel that carries the user data.

HS-PDSCH - High-Speed Physical Downlink Shared Channel:physical downlink channel that carries the user data and layer 2 overhead bits over the air interface.

HS-SCCH - High-Speed Shared Control Channel (s): physical downlink channel that carries control information how to decode the information on HS-PDSCH and which UE that shall decode it.

HS-DPCCH - High-Speed Dedicated Physical Control Channel:physical uplink channel to send ACK/NAK reports and channel quality reports

A-DCH (DPDCH+DPCCH) - Associated Dedicated Channel

uplink HS-DPCCH

The uplink HS-DSCH-related physical-layer signaling consists of:

Acknowledgements for hybrid ARQChannel Quality Indicator (CQI), i.e., information reflecting the instantaneous downlink radio-channel conditions to assist the Node B in the transport-format selection (fast link adaptation) and the scheduling

Information carried on HS-DPCCH

HS-DPCCH carries ACK/NAK and CQI from UE to RBSone HS-DPCCH for each user in the cell

ACK/NAKsingle bit, repetition coded to 10 bits (1 slot)

CQI (Channel Quality Indicator)5 bits coded to 20 bits (2 slots)channel quality measurements based on CPICHreporting rate is configurable through RRC/NBAP signaling

ACK/NAK and CQI can be repeated in multiple subframescontrolled by RRC/NBAP signalinguseful in soft handover scenarios

HS-DPCCH power control

Important to secure good success rate of ACK/NAK and CQI transmission while keeping UL interference under controlACK, NAK, CQI power offsets with relation to DPCCH set by RRC signalingTwo independent mechanisms:1. Two sets of power offsets (ACK, NAK and CQI) are configured per cell in RNC

RNC reconfigures UE depending on number of RBS involvedConfiguration changed at cell change and possibly after active set update

2. RBS initiates update of ACK/NAK and CQI feedback cycles basedon CQI detection performance

Hybrid ARQ Processes

One HARQ entity per userEach HARQ entity consist of up to 8 HARQ processes

multiple HARQ processes allows continuous transmission to a single userseparate reordering function needed to support in-order delivery

(P2 correctly received before P1 in figure below)

A-DCH, Associated Dedicated Channel

One A-DCH per HSDPA enabled terminal in the cellA-DCH is mapped on physical channels DPDCH and DPCCHA-DCH DL

3.4 kbps SRB (control signalling: RRC & NAS)A-DCH UL

384 kbps (or 64 kbps) DCH3.4 kbps SRB (control signalling: RRC & NAS)UL data transmission

Dedicated Physical Control and Data Channel (Uplink)

Dedicated Physical Control and Data ChannelDPCCH/DPDCH (Downlink)

Transport Channels and Physical Channels

Transport Channels and Physical Channels

HSDPA – summary

Documents

Mobile Package 2010