First Mobile Telephone System

First Mobile Telephone Service (MTS) was

introduced in 1946, St Loius.

Only three radio channels were available.

Call set-up required manual operation

In 1964 Improved Mobile Telephone (IMTS)

Service was introduced with additional channels

and more automatic handling of calls

First Mobile Telephone System

One and only one

high power base

station with which all

users communicate.

Entire Coverage

Area

Normal

Telephone

System

Wired connection

Draw back of conventional Mobile Telephone

Systems ?

Limitations on conventional mobile telephone systems.

Limited Service Capability

Poor Service Performance

Inefficient Frequency Spectrum Utilization

Technology and service affordability

cellular concept ..

In December 1947, Douglas H.Ring and W. Ray

Young, Bell Labs engineers, proposed hexagonal cell

concept for mobile phones.

The coverage region is divided into small cells

At this stage the technology to implement the ideas did not

exist nor had the frequencies allocation

In 1960s Bell Labs developed the electronics to achieve

this concept.

In 1970s ,the concepts of frequency reuse and handoff, as

well as a number of other concepts that formed the basis of

modern cell phone technology, were described.

In December 1971, AT&T submitted a proposal for

cellular service to the FCC.

After years of hearings, the FCC approved the

proposal in 1982 for Advance Mobile Phone System

(AMPS)

AMPS was analog in nature and called 1G.

Later AMPS was eventually superseded by Digital

AMPS in 1990.

First Mobile Cellular System

The technological development that make special

the 1G mobile phones from the previous

generation was the use of Multiple cell sites,

Ability to transfer calls from one site to the next as

the user travelled between cells during a

conversation.

Cellular Concept : An Idea which gave 1G

mobile cellular system

Replace high power transmitter with several low power transmitters to create small “cells” Multiple low-power base stations ,service mobile

users within their coverage area

Each cell assigned a set of frequencies

Neighboring cells assigned different group of frequencies to reduce adjacent-cell interference

Handoff users to neighboring base stations as users move.

First Generation (1G) Cellular System

IG (AMPS)Configuration Analog in nature

Uses FDD scheme

Down link frequency = 869-894 MHz

Uplink frequency = 824-849 MHz

Spacing between forward and reverse channel = 45 MHz

Channel bandwidth = 30 kHz

Number of full-duplex voice channels = 790

Number of full duplex control channels = 42

Data transmission rate = 10 kbps

Cell size = 2-20km radius

Second Generation (2G) Cellular System

In 1990, the 2G mobile phone systems

emerged, primarily using the GSM standard.

2G differed from the 1G by using digital instead

of analog transmission

In 1991 the first GSM network launched in

Finland.

2G Cellular Telephone Standard

Global System for Mobile (GSM) Interim Standard 136 (IS-136) Interim Standard 95 (IS-95)

Cellular Standards Evolution

Japan Europe Americas

TACS NMT/TACS/Other AMPS

PDC GSM TDMA CDMA

1st Gen

2nd Gen

GLOBAL SYSTEM FOR MOBILE

COMMUNICATION (GSM)

In 1982, European Conference of Postal and Telecommunications Administrations (CEPT) created the Group Spécial Mobile committee for developing a European standard for digital cellular voice telephony

1986 the European Commission proposed reserving the 900 MHz spectrum band for GSM.

1987, 15 representatives from 13 European countries signed a MoU in Copenhagen to develop and deploy a common cellular telephone system across Europe.

In 1989, the Groupe Spécial Mobile committee was transferred from CEPT to the European ETSI

Phase I of the GSM specifications were published in 1990.

In 1991 work begin to expand the GSM standard to 1800 MHz frequency band

In 1993 the first 1800 MHz network became operational in the UK .

July 1, 1991 The world's first GSM call was made by the former Finnish prime minister Harri Holkeri,

1992, the first SMS or "text message" was sent In 1992 Vodafone UK and Telecom Finland signed the first

international roaming agreement In 1995, fax, data and SMS messaging services were

launched commercially In 1995 the first 1900 MHz GSM network became

operational in the U.S. In 1996 Pre-paid GSM SIM cards were launched. In 2000, the first commercial GPRS services were

launched In 2002, MMS and the first GSM network in the 800 MHz

frequency band introduced. In 2003,EDGE services first became operational in a

network

1992 first paying customers were signed up for service.

By 1993 there were 36 GSM networks in 22 countries

By1994 there were 1.3 million subscribers worldwide

By 1996 there were more than 25 million subscribers worldwide

By October 1997 it had grown to more than 55 million subscribers worldwide

By 2001 , 500 million subscribers

By 2004, 1 billion subscribers

By 2005, 1.5 billion subscribers

By 2008, 2 billion subscribers

By 2012 it had more than 5 billion subscribers in 212 countries worldwide.

By 2017 it has more than 6 billion subscribers.

GSM AROUND THE WORLD

GSM (2G) GSM is a 2G cellular standard developed to cater voice and

data delivery services using digital modulation.

Properties of 2G mobile system

Good subjective speech quality

Low terminal and service cost

Support for international roaming

Ability to support handheld terminals

Support for range of new services and facilities

Enhanced Features

ISDN compatibility

Enhance privacy

Security against fraud

GSM Frequency Bands

19

GSM1800 :

Uplink : 1710-1785MHz

Down link : 1805-1880MHz

Duplex interval: 95MHz

Bandwidth: 75MHz

Frequency interval: 200KHz

GSM1900MHz:

Uplink:1850~1910MHz

Down link :1930~1990MHz

Duplex interval: 80MHz

Bandwidth: 60MHz，Frequency interval: 200KHz

GSM Specifications

GSM RF Spectrum ( 900 MHz)MS to BTS (uplink): 890-915 MHZBTS to MS (downlink): - 935-960 MHZ

Carrier Separation : 200 KHz

Duplex Distance : 45 MHz

No. of RF carriers : 124

Access Method : TDMA/FDMA

Modulation Method : GMSK

Modulation data rate : 270.833 Kbps

Three basic types of services offered

through GSM

Tele-services

Bearer or Data Services

Supplementary services

GSM Services

Tele Services

Telecommunication services that enable

voice communication via mobile phones

such as

-Telephony (Voice calls)

- Emergency calling( like 911 in USA)- SMS - Group 3 fax- Voice mailbox- Electronic mail- MMS

Bearer Services

Include various data services for information transfer between GSM and other networks like PSTN, ISDN etc at rates from 300 bps to 9.6 kbps

Supplementary services

Supplementary services are provided on top of tele-services or bearer services, and include features such as

caller identification

call forwarding

call waiting

multi-party conversations

barring of outgoing calls

GSM Architecture

PSTN

Data Terminal

HLR/VLR

MSCBSC

OMC(Operation & Maintenance

Center)

OperationTerminal

BTS

HandsetA

X.25

A-bisSS7

Network sub-system PSTNRadiosub-system

Mobilestation

UM

SIMcard

AUC/EIR

Base Station Subsystem is composed of following

parts

1. Base Station Controller (BSC)

2. Base Transceiver Station (BTS)

Base Station Controller (BSC)

Communicate with MSC and BTS

Most robust element in the BSS

Provides, the intelligence behind the BTS.

has 16 to 512 of BTS under its control.

One BSC Support ( 20000- 45000 ) subscriber

Function of Base Station Controller

(BSC)

Manages Radio resources for BTS ( Assigns Frequency and time slots for all MS’s in its area )

Handle call set up

Provide Handover to MS

Control Radio Power

Transcoding and rate adaptation functionality

BSC

Typical GSM BTS

What a GSM cell site consist

A Shelter

Tower

BTS Shelter Layout

AC-2

AC-1

DDF

BTS

Cabinet

PIU

SMPS Battery

Bank

DO

OR

MCB1

MCB2

Types of Tower

Ground Base Tower(GBT)

Roof Top Tower(RTT)

In Building Solution(IBS)

Types of BTS

Ultra wave BTS

Flexi BTS

Ultra Wave BTS

can support max. of 12 TRx card.

One TRx card supports 8 time slots( i.e. max of 8 users),

Capacity in terms of users can be increased using Half

rate, ( one time slot is assigned to 2 users in Half rate)

It has all Pin connections on back side

Ultra wave BTS

Flexi BTS

Flexi can support max. of 24 TRx.

Easier site construction, with easier implementation

lower installation costs

Reduced demand for power, resulting in smaller power systems

All connections are on front side so it is easy to install every equipment.

FLEXI BTS

NOKIA BTS CABINET 4X4X4

CONFIGURATION

NOKIA BTS CABINET 4X4X4 CONFIGURATION

DVJA

M2HA

M2HA

M2HA

M2HA

M2HA

TRX-0

TRX-6

TRX- 9

TRX-10

TRX-11

TRX-7

TRX-8

TRX-5

TRX-1

TRX-3

TRX-4

TRX-2

M2HA

DVJA

DVJA

DVJA

DVJA

DVJA

BIO

A

PW

SB

PS

WB

PW

SB

BB

F1

BB

F2

BB

F3

BB

F4

BB

F5

BB

F6

VxR

B

VxR

B

VxR

B

VxR

B

Β

Sector

α

Sector

¥

Sector

WCHA

WCHA

WCHA

TRx-Transmitter/Receiver cards

WCHA-Wide (band) channel Amplifier Duplexer

(Combiner)

PWSB- Power Supply B card

BOIA-Base operation Interface Amplifier

BBF-Base band filter

M2HA-Multi coupler

Vx RB or RRI card (Radio Relay Interface)

DVJA

Transceiver (TRX)

Basically does transmission and reception of signals. Sending and reception of signals to/from higher network

entities (like the BSC) Can support 8 user at a time in Ultra BTS and 24 users in

Flexi BTS - Prize 1 Lac approx

BOIA-Base operation Interface Amplifier

- Power amplifier

-Brain of BTS

-Amplifies the signal from TRX for transmission through antenna; may be integrated with TRX.

-Support 2TRx

WCHA-Wide band Amplifier Duplexer

It works as a Combiner

Combines feeds from several DRXs so that they could be sent out through a single antenna

allows for a reduction in the number of antenna used.

Base Band Filter(BBF)

Filter baseband signal coming from user

Frequency hopping, signal DSP, etc.. Support 2 TRx

Dual Variable Gain Amplifier(DVGA)

The filtered input signal is level controlled using a variable

gain amplifier (VGA) or a variable attenuator and amplifier

combination.

The signal is then sent to a demodulator RF integrated

circuit (RFIC) where it is demodulated into in-phase (I) and

quadrature phase (Q) baseband signals.

Network Switching Subsystem

(NSS)

NSS carries out switching functions and manages the communications between MS and the PSTN.

It is owned and deployed by mobile phone operators

Function of Network switching subsystem

(NSS)

Nerve Centre of entire GSM network

Manages all call processing subscriber

related functions

Contains

the core switching component

a number of databases

Gateways to other networks

Uses Signaling System Number 7 (SS7)

Components of NSS Network ?

NSS contains following nodes

MSC

VLR

HLR

AUC

EIR

Mobile Switching Center (MSC)

Heart of the network

Manages communication between GSM and other networks

Call setup function and basic switching

Call routing

Billing information and collection

Mobility management

- Registration

- Location Updation

- Inter BSS and inter MSC call handoff

MSC does realize these functions with conjunction of following 4 intelligent data base HLR

VLR

EIR

AUC

Home Location Registers (HLR)

Contains the administrative information of each of the subscriber registered in the network

Keep permanent copy of the subscriber data

Logically one HLR per PLMN,

HLR maps each IMSI with a unique mobile phone number called Mobile Subscriber ISDN (MSISDN).

HLR also holds most of the information held by the SIM such as IMSI, MSISDN, prepaid/postpaid, roaming restrictions, supplementary services etc.

Visitor Location Registers (VLR)

Temporary database which updates whenever

new MS enters its area, by HLR database

Controls those mobiles roaming in its area

Database contains IMSI, TMSI, MSISDN,

MSRN, Location Area, authentication key

Authentication Center (AUC)

AuC is a function to authenticate each SIM

card that attempts to connect to the GSM core

network

After successful authentication , HLR is

allowed to manage the SIM and services

Protects against intruders in air interface

Maintains authentication keys and algorithms

and provides security triplets ( RAND,

SRES,Kc)

Generally associated with HLR

Equipment Identity Register (EIR)

- Database that is used to track handsets

using the IMEI (International Mobile

Equipment Identity)

- Made up of three sub-classes: - The White List,

- The Black List

- The Gray List

- Only one EIR per PLMN

Other Network Components

Operations & Maintenance Subsystem(OMS)

Enhanced Services Subsystem (ESS)

Critical :-Immediate action

Major :- As soon as possible

Minor :- Action can be taken when there is time

Warning :-Point out conditions and corrective

Action is then taken during schedule maintenance

Indeterminate :- shows that an alarm has been

Generated for which there is no alarm severity

In the system.?

OMS

OMS is used to configure, control and to

monitor the GSM network.

It comprises of two parts:

Operation and Maintenance Centre - Switch

Operation and Maintenance Centre - Radio

Advantages of GSM

Less signal deterioration inside buildings,

Ability to use repeaters

Talk time is generally higher in GSM phones due to the pulse nature of transmission.

The availability of SIM allows users to switch networks and handsets at will,

GSM covers virtually all parts of the world so international roaming is not a problem.

The much bigger number of subscribers globally creates a better network effect for GSM handset makers, carriers and end users.

Disadvantages of GSM

Interferes with some electronics, especially certain audio

amplifiers.

Intellectual property is concentrated among a few

industry participants, creating barriers to entry for new

entrants and limiting competition among phone

manufacturers.

GSM has a fixed maximum cell site range of

120 km, which is imposed by technical limitations

This is expanded from the old limit of 35 km.

PSTN

HLR/

VLR

MSCBSC

BTS

MS

SS7GMSC1

10

1 23 4

5 6

7899

Mobile Originated Call

Mobile Originated Call

1. MS sends dialled number to BSS

2. BSS sends dialled number to MSC

3,4 MSC checks VLR if MS is allowed the requested service . If so, MSC asks BSS to allocate resources for call.

5 MSC routes the call to GMSC

6 GMSC routes the call to local exchange of called user

7, 8,

9,10 Answer back(ring back) tone is routed from called user to MS via GMSC,MSC,BSS

PSTN

HLR/AUC

MSCBSC

MS

SS7GMSC

1

3

4

5

27

9

VLR

68

10

11

12

13

14 15

16

10

13

17

Mobile Terminated Call

Mobile Terminated Call1. Calling a GSM subscribers

2. Forwarding call to GSMC

3. Signal Setup to HLR

4. 5. Request MSRN from VLR

6. Forward responsible MSC to GMSC

7. Forward Call to current MSC

8. 9. Get current status of MS

10.11. Paging of MS

12.13. MS answers

14.15. Security checks

16.17. Set up connection

CDMA (Code Division Multiple Access)

Limitations of conventional FDMA and TDMA

Each channel is allocated a disjoint frequency or time slot

Channel capacity is limited by BW and time allotment, thermal

AWGN, and propagation effect (shadowing and multipath fading)

Frequency reuse needs a very careful design because of potential

co-channel interference.

FDMA and TDMA suffer degradation due to multipath fading

Spread Spectrum multiple access can overcome most of the

limitations of conventional systems.

Fast Network deployment.

Reduced service interruptions

Low Maintenance & operational cost

Better system coverage flexibility

Higher capacity

Anti-jamming (A/J) & Anti Interference (A/I)

Resistance to interception

Message Privacy

ADVANTAGES OF CDMA

Advantages of CDMA

Capacity is biggest asset; it can accommodate more users per MHz

of bandwidth than any other technology.

Has no built-in limit to the number of concurrent users.

Consumes less power and covers large areas so cell size in IS-95 is

larger.

Able to produce a reasonable call with lower signal (cell phone

reception) levels.

Uses soft handoff, reducing the likelihood of dropped calls.

What is CDMA ?

CDMA is a wireless communications Access

technique that uses the principle of spread spectrum .

Users are separated by codes.

WHAT IS MULTIPLE ACCESS ?

NUMBER OF USERS ACCESS AND SHARE

• TRANSMISSION MEDIUM

• BANDWIDTH AVAILABLE

FOR COMMUNICATION AT THE SAME TIME.

Multiple Access scheme

72

CDMA Evolution 1Gbps

153.6kbps

CDMA

1xRTT

CDMA

1xEV-DV

CDMA

IS-95

CDMA

1xEV-DO

2G 2.5G3G

9.6kbps

4G

2Mbps4G

What is Spread Spectrum A means of transmission in which the data

occupies a B.W in excess of the minimum bandwidth necessary to send it.

Signal spreading is done before transmission by using a spreading sequence.

The same sequence is used at the receiver to retrieve the signal

SPREAD SPECTRUM CAPACITY

SS Capacity can be calculated by Shannon’s Equation

C= W Log (1+S/N)

Where C=Capacity (bps)

W=Bandwidth

S=Signal Power

N=Noise Power

Processing Gain

The value of processing gain (G) ranges from 102 to 106

(20 to 60 dB)

Higher processing gain results in greater immunity

to noise, and interfering signals.

Frequency Bands

CDMA 824- 849 MHz

869- 894 MHz

PCS 1850- 1910 MHz

1930- 1990 MHz

A

A

A

AA

A

A

AA

A

A

AA

A

A

AA

A

A

AA

A

A

A

AA

A

A

CDMA Frequency Reuse

Frequency Reuse

C

D

B

AC

F

G

EB

A

E

GB

D

C

FE

G

F

CE

B

D

C

FD

B

A

Frequency Reuse pattern of 7 GSM

Anti-Jamming (A/J) & Anti Interference

(A/I)

Real beauty of SS.

Intentional or un-intentional interference and jamming

signals are rejected without the right key .

Only the desired signal, which has the key, will be seen

at the receiver when de-spreading operation is

exercised.

Spread Spectrum Principle

The signal spread on a bandwidth much

greater than that which is necessary to

send the information or data with the

help of spreading code .

84

Spreading Codes ?

A noise-like and random signal

Generated at the transmitter.

The same signal must be generated at the receiver in

synchronization.

Spread and de-spread with the matched code results in

detection

Spread and de-spread with the wrong code results in

interference

The code must satisfy some properties

Assume a sequence

S={(000111101011001),(010011010111100)}

Balance property:-Relative frequencies of “0”

and “1” should be ½

Run Property: Run lengths of zeros and ones

should be

Half of all run lengths should be unity

One - quarter should be of length two

One - eighth should be of length three

Correlation

The concept of determining how much similarity one set of data has with another

Range between –1 and 1

1 The second sequence matches the first sequence

0 There is no relation at all between the two sequences

-1 The two sequences are mirror images

Cross correlation

The comparison between two sequences from different sources rather than a shifted copy of a sequence with itself

Cross-correlation is a measure of similarity of two waveforms as a function of a time-lag applied to one of them.

Autocorrelation property :- Autocorrelation is the cross-

correlation of a signal with itself.

If the random sequence is shifted by any nonzero number of elements, the

resulting sequence should have an equal number of agreements and

disagreements with the original sequence

Types of Spreading (Codes)Sequence

CDMA system uses two types of (code) sequence

Pseudorandom Noise (PN) Sequences.

Long codes (242 =4400 Billion)

Short codes (215 =32768)

Walsh codes (Orthogonal Sequences )

Random Codes

Ideal but not practical

A truely random process cannot be duplicated

In SS , the spreading sequence must be easily

generated and duplicates (copies) of the code

must be reproducible at the receiver.

Pseudo -Noise (PN) Sequences

PN Sequences are periodic, deterministic and binary

sequences with a noise like wave form

Known as Pseudo -random since it looks randomly for the

user who does not know the code

The longer the period of PN spreading code, the harder to

be detected sequence

The sequence can be generated using feedback shift

registers which are made up of m flip flops -that have two

states memory stages and logic circuit .

There are many types of code (Gold, m-sequence, Walsh-

Hadamard, etc)

PN Codes are generated from prime polynomials using

modulo-2 arithmetic.

Consists of shift registers & XOR gates.

The length (period)of the PN Code is equal to 2m -1 ( m=

no. of shift registers).

Some Terminology Related To The Pseudo-random Code:

Chipping Frequency (fc): the bit rate of the PN code

Chipping interval : 814 nsec

Information rate (fi): the bit rate of the digital data.

Chip: One bit of the PN code.

Epoch: The length of time before the code starts

repeating itself (the period of the code).

CDMA Codes Summary

Walsh Codes

Short PN Sequences

Long PNSequences

Type of Sequence

Mutually Orthogonal

Orthogonal with itself at any time shift value except 0

near-orthogonal if shifted

Special Properties

64

2

1

How Many

64 chips1/19,200 sec.

32,768 chips26-2/3 ms

75x in 2 sec.

242 chips~41 days

Length

Orthogonal Modulation

(information carrier)

Quadrature Spreading (Zero offset)

Distinguish users

Reverse Link Function

User identity

within cell’s signal

Distinguish Cells & Sectors

Data Scrambling to avoid strings of 1’s

or 0’s

Forward Link Function

Generation 1G 2G 2G 3G 3G 4G

NAME OF STADARD NMT GSM

IS-95 (CDMA

one)

UMTS (3GSM)

IS-2000

(CDMA 2000)

LTE

Year of First Use 1981 1991 1995 2001 2000 / 2002 2009

Technology( Multiple access

technique)FDMA TDMA & FDMA CDMA W-CDMA CDMA OFDMA

Encoding Analog Digital Digital Digital Digital Digital

Handset interoperability None SIM card None SIM card RUIM SIM card

Handoff Hard Hard Soft Soft Soft Soft

Voice and Data at the same

timeNo Yes GPRS No Yes No EVDO /

Yes SVDO

No (data only)Voice

possible though

Common

NameFamily Primary Use Radio Tech

Down

stream

(Mbps)

Up

stream

(Mbps)

Notes

EDGE

EvolutionGSM Mobile Internet TDMA/FDD 1.6 0.5 3GPP Release 7

EV-DO CDMA2000 Mobile Internet CDMA/FDD

2.45

3.1

4.9xN

0.15

1.8

1.8xN

Rev B note: N is

the number of

1.25 MHz carriers

used. EV-DO is not

designed for voice,

and requires a

fallback to 1xRTT

when a voice call

is placed or

received.

NameFamily Primary Use Radio Tech

(Mbps) (Mbps)Notes

HIPERMAN HIPERMAN Mobile Internet OFDM 56.9

HSPA+ 3GPP 3G DataCDMA/FDD

MIMO

21

42

84

672

5.8

11.5

22

168

HSPA+ is widely

deployed.

Revision 11 of

the 3GPP states

that HSPA+ is

expected to

have a

throughput

capacity of

672 Mbit/s.

LTE 3GPP General 4GOFDMA/MIMO

/SC-FDMA

100 Cat3

150 Cat4

300 Cat5

(in 20 MHz

FDD)

50 Cat3/4

75 Cat5

(in 20 MHz

FDD)

LTE-

Advanced updat

e expected to

offer peak rates

up to 1 Gbit/s

fixed speeds

and 100 Mb/s to

mobile users.

UMTS W-

CDMA

HSPA(HSDPA

+HSUPA)

UMTS/3GS

MGeneral 3G

CDMA/FDD

CDMA/FDD/MI

MO

0.384

14.4

0.384

5.76

HSDPA is widely

deployed.

Typical downlink

rates today

2 Mbps,

~200 kbps

uplink; HSPA+

downlink up to

56 Mbit/s.

LTE 3GPP General 4GOFDMA/MIMO/SC

-FDMA

100 Cat3

150 Cat4

300 Cat5

(in 20 MHz

FDD)[

50 Cat3/4

75 Cat5

(in 20 MHz

FDD)

LTE-

Advanced update

expected to offer

peak rates up to

1 Gbit/s fixed speeds

and 100 Mb/s to

mobile users.

UMTS W-

CDMA

HSPA(HSDPA+

HSUPA)

UMTS/3GSM General 3G

CDMA/FDD

CDMA/FDD/MIMO

0.384

14.4

0.384

5.76

HSDPA is widely

deployed. Typical

downlink rates today

2 Mbit/s, ~200 kbit/s

uplink; HSPA+

downlink up to

56 Mbit/s.

UMTS-TDD UMTS/3GSMMobile

InternetCDMA/TDD 16

Reported speeds

according

toIPWireless using

16QAM modulation

similar

toHSDPA+HSUPA

Wi-Fi802.11

(11n)Mobile Internet OFDM/MIMO

288.8 (using 4x4 configuration in

20 MHz bandwidth) or 600 (using 4x4

configuration in 40 MHz bandwidth)

Antenna, RF

front

endenhanceme

nts and minor

protocol timer

tweaks have

helped deploy

long

range P2Pnetw

orks

compromising

on radial

coverage,

throughput

and/or spectra

efficiency

(310 km & 382 k

m)

WiMax rel 1 802.16 Wireless MANMIMO-

SOFDMA37 (10 MHz TDD)

17 (10 MHz

TDD)With 2x2 MIMO

WiMax rel 1.5802.16-

2009Wireless MAN

MIMO-

SOFDMA

83 (20 MHz TDD)

141 (2x20 MHz FDD)

46 (20 MHz

TDD)

138 (2x20 MHz

FDD)

With 2x2

MIMO.Enhance

d with 20 MHz

channels in

802.16-2009

WiMAX rel 2 802.16m WirelessMANMIMO-

SOFDMA

2x2 MIMO

110 (20 MHz TDD)

183 (2x20 MHz FDD)

4x4 MIMO

2x2 MIMO

70 (20 MHz

TDD)

188 (2x20 MHz

FDD)

4x4 MIMO

Also, low

mobility users

can aggregate

multiple

channels to get

Three Core concept Of cellular system

There are three core concept which works behind

cellular system

Cell( which tessellate overall coverage area)

Frequency reuse

Handoff

Instead of one cell(covering area) with one

high power transmitter ,the entire city or

covering area is broken up into smaller

area which is called cell.

City is divided in hexagonal cell

Cell

Each of these smaller coverage areas has its

own low power base station.

User phones in one cell communicate with the

base station in that cell.

Why Hexagon Cell ? Ideally base stations have identical, circular

coverage areas

Circles may be good option but circles Don’t

Tessellate

The most circular of the regular polygons that

tessellate is the hexagon.

Thus, early researchers started using hexagons

to represent the coverage area of a base station

which is called cell.

What is Cell ?

A cell is the basic geographical unit of a

cellular System

Defined as the area where radio coverage is

given by one base station.

Types of Cells

On the basis of coverage area, cells may be

classified as

Macro cell

Micro cell

Pico cell

Femto cell

Macro cell

radius (1-35)Km

used in rural areas or along highways

provide coverage to larger area .

The antennae for macro cells are mounted on

ground-based masts, rooftops etc

Micro cells

have the radius (2-8)Km

used in a densely populated urban area

Pico cells

have the radius 100m - 1km

used in large office, a mall, or train station.

Femto Cells

have the radius (10-100) m

used in homes or small offices.

Frequency Reuse

Though the first mobile system achieve its goal

for large coverage area but it was no option to

reuse the frequency.

In proportion of mobile users demand,

government regulatory authority could not

allocate spectrum

So there was a strong need to restructure the

mobile system to achieve capacity with coverage.

Need Of frequency Reuse

Frequency spectrum is a scarce

GSM is not used for voice communication, but it is also used for

data communications .

e.g 900MHz band have 25 MHz frequency band which account to

a maximum of 125 frequency channels

Within an eightfold time multiplex for each carrier ,a maximum of

1000 channels can be accommodated .

This number is further reduced by guard bands and the overhead

required for signaling .

Frequency reuse -

To serve several millions of subscribers

,frequencies must be spatially reused .

This concept led to the development of cellular

technology ,

This allowed a significant improvement in the

economic use of frequencies for capacity and

coverage.

an intelligent Frequency allocation Planning

The solution ,the industry adopted is called frequency planning or frequency Reuse.

Each BTS is allocated a group of radio channels to be used within a cell.

The same group of channels may be use in other cell in particular cell which is called frequency reuse.

So, the capacity of a cellular system is directly proportional to the number of times a cluster is replicated in a fixed service area.

It is decided by Frequency reuse Distance(D) ?

The distance between two centre of co-

channel cell is called frequency reuse distance

(D)

The frequency reuse distance (D) is given by

D= R

where N=i²+ij+j²

R= Radius of the cell

N=No. of cells in a cluster

The cells which use the same set of frequency are called co-channel cell

Co-channel cell

Locating co-channel cell ?

Move i cells along any chain of hexagon

Turn 60 degree counter clockwise.

Move j cells

Example

Let i=1,j=2 then N=7

A Group of cell is called cluster and denoted by N.

N=i²+ij+j²

Where i & j are non negative integers.

The factor N is called the cluster size.

the number of cell per cluster, N, can only have values

which satisfy the equation.

N=i²+ij+j²

(i, j) N(1,1) 3

(2,0) 4

(2,1) 7

(3,0) 9

(2,2) 12

(3,1) 13

(3,2) 19

Design Objectives for Cluster

formation

High spectrum efficiency

Required : many users per cell

Remedy : small cluster size gives much

bandwidth per cell

Drawback: More interference or low QoS

High performance

Required : Little interference

Remedy : Large cluster sizes

Drawback :less users per cell

All the best…