Lecturer: Michael O'Grady

Course: MSc Ubiquitous & Multimedia Systems

Unit: Context Sensitive Service Delivery

Lecture:

Wireless Network Structure

Objectives

Describe GSM Outline the evolution of GSM to 3G Describe the implications for

services of this evolution. Review the Cellular Concept Introduce WiFi, Bluetooth and

Satellite telephony Introduce Software Defined Radio

History of GSM - I

1982Group Spéciale Mobile formed (origin of term GSM)

1897 Initial Memorandum of Understanding (MoU) signed by network operators representing 12 countriescoordinate introduction of GSMagree time scalesplan the introduction of servicescoordinate routing, billing and tariffs

1988 - Validation & trials

History of GSM - II

1989 - European Telecommunications Standard Institute (ETSI) formed

1991 - Launch delayed due to lack of mobiles

1992 - Officially launched 1993 - Commercial services start

outside Europe 2003 - Over 200 countries 2004 - Over 1 billion subscribers?

Ref: http://www.gsmworld.com

Anticipated Benefits of GSM

Superior speech qualityLow terminal costsBetter securityLow power portable terminalsSupport for international roamingNew services

Motivations for GSM

Political Considerations Impending EU unification Deregulation of mobile telephony

Economic Considerations single market cost benefits through economies of

scale potential for export

GSM Services - Phase 1

Service Category Service CommentsTeleservices Speech

EmergencySMS (Short Message Service)

Group 3 Fax

Full Rate 13KbpsPoint to Point & Cell Broadcast

Bearer Services Asynchronous DataSynchronous Data

300 – 9600bps300 – 9600bps

Supplementary Services Call ForwardCall Barring

Subscriber Busy, Not ReachableInternational & Incoming Calls

GSM Services - Phase 2

Service Category Service CommentsTeleservices Speech

EmergencySMS (Short Message Service)

Group 3 Fax

Half Rate 6.5KbpsPoint to Point & Cell Broadcast

Bearer Services Synchronous Packet Data Access 2400 – 9600bpsSupplementary Services CLI (Calling Line Identification)

Call WaitingCall HoldMultiparty

USSD (Unstructured SupplementaryService Data)

Operator BarringAdvice on charge

GSM Services - Phase 2+

Primarily concerned with the improvement of Bearer (data!) services Full data rate @ 14.4 kb/s High Speed Circuit Switched Data (HSCSD) General Packet Radio Service (GPRS)

Some additional supplementary services also specified

The GSM Family - 1

GSM 900 Uplink - 890 MHz to 915 MHz Downlink - 935 MHz to 960 MHz

GSM 1800 Also known as

PCN (Personal Communications Network) DCS 1800 (Digital Cellular System 1800)

Uplink - 1710 MHz to 1785 MHz Downlink - 1805 MHz to 1880 MHz

The GSM Family - 2

GSM 1900also known as PCS 1900/DCS 1900deployed main in North America

Uplink - 1850 MHz to 1910 MHz Downlink - 1920 MHz to 1990 MHz

Dual-Mode/Tri-band phonesRoaming agreement necessary

Architecture of a GSM Network

SD

Mobile Station

BTS

MSC/VLR

SIM MEBSC

Base StationSubsystem

GMSC

Network Subsystem

AUCEIR HLR

Other Networks

Note: Interfaces have been omitted for clarity purposes.

+

PSTN

PLMN

Internet

Mobile Station (MS)

Mobile Equipment• Fixed• Portable

International Mobile Equipment Identity (IMEI) number

Subscriber Identity Module (SIM) Personal Identification Number (PIN) International Mobile Subscriber Identity

(IMSI) number Enables access to subscribed services Smart card

Interfaces in GSM

Interfaces of fundamental importance and documented by the standardization organizations Interface Definition

An Interface may be defined by a set of technical characteristics describing the point of connection between two

telecommunication entities. For example, the connection between a telecommunication network and the customers apparatus.

Example: Air Interface (Um Interface) Interface between Mobile Station and Base

Station Subsystem

Base Transceiver Station - BTS

Usually referred to as the Base Station Provides the interface to the network for

the MS Handles all communications with the MS Less “intelligent” than analogue

equivalent cheaper than analogue systems bypass analogue in less wealthy countries

“intelligence” now deployed on MS for example, when to perform a handover

Transmitting power determines cell size

Base Station Controller - BSC

Controls Base Stationsup to several hundred depending on

manufacturer

Manages radio channelsallocation and release

Coordinates Handover Physical location may vary Abis interface

between BSC and BTS

Network SubSystem(NSS)

Nerve Centre of entire GSM networkManages all

call processingsubscriber related functions

Contains the core switching component a number of databases gateways to other networks

Uses Signalling System Number 7 (SS7)

Mobile Switching Centre (MSC)

Performs all switching/exchange functions Handles

• registration• authentication• location updating

A GSM network must have at least one MSC

May connect to other networks Gateway MSC (GMSC)

Home Location Register (HLR)

Administrative information for all subscribers IMSI number actual phone number permitted supplementary services current location i.e. which VLR subscriber is

currently registered with parameters for authentication and ciphering

One HLR per GSM PLMN

Visitor Location Register (VLR)

Contains data on all MSs currently in the area served by the MSC permanent data (identical to that in HLR) Consulted during

call establishment caller authentication

Usually integrated with MSC so that geographic area covered by both coincides signalling requirements simplified considerably

Equipment Identity Register (EIR)

Maintains lists of IMEI numbers of all valid and invalid equipment for the network

• IMEI - International Mobile Equipment Identity

An IMEI may be invalid if stolen not approved for use on the network,

possibly due to some defectEIR consulted during registration/call

setup

Authentication Centre (AUC)

Protected database Stores all algorithms used for

authentication purposes Knows which one has been issued to the

subscriber (stored on SIM card) provides HLR or VLR with parameters for

completing authentication

Other Network Components

Operations & Maintenance Centre Intelligent Networking Billing Centre SMS Gateway

Integrating GPRS

SD

Mobile Station

BTS

MSC/VLRBSC

Base StationSubsystem

GMSC

Network Subsystem

AUCEIR HLR

Other Networks

Note: Interfaces have been omitted for clarity purposes.

GGSNSGSN

SIM ME

+

PSTN

PLMN

Internet

GPRS MS

Two Components• Mobile Terminal (MT)• SIM card

Three Classes of terminal• Class A - simultaneous circuit switched (GSM)

and packet switched (GPRS) traffic• Class B- supports both GSM and GPRS

connections but not both at the same time. One call is suspended for the duration of the other

• Class C - handless both GPRS or GSM but can only be connected to one at the same time.

GPRS BSS

GPRS has minor impact on the BSS Packet Control Unit introduced

Usually integrated into the BSC Essentially, a software update

GPRS NSS

Two new nodes introduced for packet data Serving GPRS Support Node (SGSN)

handles all packet data for the appropriate geographic area• monitors GPRS users• handles security and access control• may be regarded as the packet switched equivalent of

the circuit-switched MSC

Gateway GPRS Support Node (GGSN)• internetworking functionality• routes incoming data to correct SGSN• translates between different protocols and formats

Details of data services added to HLR

GPRS - Summary

Data capacity increased considerablyDepending on configuration

@ 14.4 kb/s per channel, 115.2 kb/s achieved@ 21.4 kb/s per channel, 171.2 kb/s achieved

BUT up to 8 users per channel!Minimum set-up time“always-on” connectionCharging determined by actual data not

time

Integrating EDGE

Minimum changes to the existing network

New Modulation scheme 8 phase shift keying (8PSK) 3 bits of information per signal pulse data rates increased by a factor of three

EDGE - MS

Upgrade is necessarySituated complicated by

higher data rates on the downlink only

higher data rates on both the uplink and downlink

EDGE - BSS

Significant changes software upgrades on all BTSs and

BSCs New transceiver unit for all BTSs

support legacy GSM & GPRS traffic switch to EDGE only as required

EDGE - NSS

Minimum impact on the core network

SGSN & GGSN practically independent of data rates

Some minor software upgrades

3G - UMTS

SD

Mobile Station

MSC/VLR

Base StationSubsystem

GMSC

Network Subsystem

AUCEIR HLR

Other Networks

Note: Interfaces have been omitted for clarity purposes.

GGSNSGSN

BTS BSC

NodeB

RNC

RNS

UTRAN

SIM ME

USIMME

+

PSTN

PLMN

Internet

UMTS - MS

User Equipment Mobile Equipment UMTS SIM (USIM)

Air interface UMTS Terrestrial Radio Access (UTRA)

• W-CDMA• TD-CDMA

UMTS BSS

Radio Network SubsystemTwo new network elements

Node B equivalent of a BTS

Radio Network Controller supports a number of Node Bs equivalent of a BSC

Obviously, UMTS has major implications for the BSS

UMTS NSS

Core Network (CN)Minimum changes

mainly software upgrades

Enabling UMTS Services - 1

Some initiatives launched to aid the deployment of new services Mobile Station Execution Environment (MExE)

categorize handsets using classmarks

SIM Application Toolkit (SAT) standardized execution environment ensures interoperability between any SIM and any

ME

Virtual Home Environment (VHE) roaming users enjoy the same standard of services

and the exact same services wherever they roam.

Enabling UMTS Services - 2

Customised Applications for Mobile networks Enhanced Logic (CAMEL) essential for the VHE

Open Services Access (OSA) provides a standard scalable and

extensible interface through which standard network functionality can be accessed

Recall propriety nature of telecommunications networks!

Other Initiatives

Parlay ConsortiumJava Intelligent Network Initiative

(JAIN)Mobile Games Interoperability Forum

(MGI Forum)M-Services

GSM Association Common set of services available

globally

The Cellular Principle

Relies on the concept of concurrency delivered through channel reuse i.e. reusing

channels in different cells

Total coverage area is divided into cells only a subset of channels available in each cell

All channels partitioned into sets sets assigned to cells

Rule: assign the same set to two cells that are sufficient geographically distant so that interference is small

Net result: increased capacity!

Advantages of Cellular Networks

More capacity due to spectral reuseLower transmission power due to

smaller transmitter/receiver distancesMore robust system as Base Station

problem only effects the immediate cell

More predictable propagation environment due to shorter distances

Disadvantages of Cellular Networks

Need for more infrastructureNeed for fixed network to connect

Base StationsSome residual interference from co-

channel cellsHandover procedure required

WiFi

Wireless Fidelity (WiFi)IEEE 802.11b50m range approximatelyData rates vary

11 Mb/s in theory 7 Mb/s is more realistic

Walls can reduces range and throughput

Number of users can reduce data rates

WiFi Problems

Security WiFi was not designed with robust

security in mindInterference

operates in unlicensed 2.4 GHz spectrum

competes with other products e.g microwave ovens!

Scarcity of “hotspots”

Bluetooth

1998Goal: eliminate the need for cablesShort range - 10mdata rate - 1 Mb/sExample of an ad-hoc network

network formed on an “as-needed” basis

Bluetooth Topology

Piconet Two or more Bluetooth devices One master

regulates traffic between devices

Remainder termed slaves Scatternet

Two or more piconets Note that a device can be a member of

more than one piconet at a given time.

Satellite Telephony

TYPE Altitude Characteristics Examples

GEO

(Geosynchronous

Earth Orbit)

35,800km Large coverage footprint

Small number of satellites

Large propagation delay

High power requirements

INMARSAT

LEO

(Low Earth Orbit)

Between

500km and

1500km

Small coverage footprint

Larger number of satellites

Faster response time

Low power requirements

Short life span of satellites

(due to increased radiation

at low altitudes)

Iridium

GlobalStar

MEO

(Medium Earth

Orbit)

Between

5000km

and

12000km

Essentially a compromise

between GEO and LEO

satellites with the respective

advantages and disadvantages

being affected accordingly.

Odyssey

ICO

Software Defined Radio

Incompatible technologies Gardai, Fire brigade etc Different protocols, air interfaces etc Legacy telecommunications systems

Solution Implement modules in software!

Power consumption ….Additional Processing required

Goal – Ubiquitous Connectivity….

Cognitive Radio

3G – cellular parameters fixedSDR – parameters dynamicCR – parameters “intelligently”

adapted Sense environment – usage patterns etc Learn patterns, rules etc Act accordingly

Note: most spectrum unused!!!!!!!!!Objective – maximise spectrum efficiency

Summary

Examined GSMTraced the proposed migration of

GSM to 3GOutlined some implications for data

servicesIntroduced some additional wireless

technologies including Bluetooth, WiFi and Satellite telephony

The End