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GSM MOBILE

COMMUNICATIONSPresented By:

Sri Subhrajit Roy

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Brief History

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MOBILE COMMUNICATION

. MOBILE COMMUNICATION IS A VERY RAPIDLY

GROWING AND A POPULAR SERVICE.

PART - I : A Brief History

. REVOLUTION IN TELECOM.

. APPROXIMATELY 50 FOLD INCREASE IN LAST 10 YEARS

• IT ALLOWS TO COMMUNICATE TO PEOPLE

WITH ANYBODY WHILE ON MOVE

(PH ONES F OR TH E PEOPL E , NOT F OR TH E PL ACES) • PROVIDES VOICE , FAX, DATA

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MOBILE COMMUNICATION

• 1 G (AMPS, TACS) -analog (cellular revolution)- only mobile voice services

WIRELESS GENERATIONS

• 2 G (GSM, CDMA) - breaking digital barrier - mostly for voice services&

data delivery possible

• 3 G - Voice & data ( breaking data barrier)- Mainly for data services where voice

services will also be possible

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Cellular Concepts

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• Any time Anywhere• Mobility & Roaming• High capacity & subs. density

• Efficient use of radio spectrum• Seamless Network Architecture• Low cost• Innovative Services

• Standard Interfaces

MOBILE COMMUNICATION

OBJECTIVES

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CELLULAR CONCEPTS

WHAT IS A CELL ?

• Area covered by a base station transmitter having a numberof RF channels is called a cell

• Each cell covers a a limited number of mobile subscriberswithin the cell boundaries ( Coverage area of the cell)

• Typical Cell Radius :

Approximately:• 25 Km (Start up)• 1 Km (Mature)

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Representation of Cells

Ideal cells Fictitious cells

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Cellular Coverage

• Coverage zone is divided into cells served by transmitters using towers.

• Each transmitter is assigned a portion of the available channels.• After a sufficient distance, the same

channels are re-used to increase spectrumefficiency

CELLULAR CONCEPTS

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Network Architecture

BTS

MSC VLR

HLR

PSTNISDN

Data

Networks

(

Air interface

OSS

BTS

BTS

MSC VLR

BSCBSC

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Tri-Sector antenna for a cell

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FUNCTION OF BTS

• BTS mainly consists of a set of transceivers(TRX). Can accommodate 1 to 7 TRX per Sector

• Random access detection

• Uplink radio channel measurements

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FUNCTIONS OF BSC

• Intermediate connectivity between BTSand MSC

• Radio resource management• Inter-cell handover • Reallocation of frequencies

• Power control

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MSC ( MOBILE SWITCHING CENTRE )

• Call setup functions, basic switching aredone

• Manages communication between GSM &

other network• MSC takes into account the RR allocation in

addition to normal exchange functions

• MSC does gateway function while itscustomers roams to other network by usingHLR /VLR

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Overview of 3G

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Why 3G?

Higher bandwidth enables a range of newapplications!!For the consumer

Video streaming, TV broadcast

Video calls, video clips – news, music, sportsEnhanced gaming, chat, location services…

For businessHigh speed teleworking / VPN accessSales force automationVideo conferencingReal-time financial information

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cdmaOne

GSM

TDMA

2G

PDC

CDMA20001x

First Step into 3G

GPRS 90%

10%

Evolution of Mobile Systems to 3G- drivers are capacity, data speeds, lower cost of deliveryfor revenue growth

EDGE

WCDMA

CDMA2000

1x EV/DV

3G phase 1 Evolved 3G

3GPP CoreNetwork

CDMA20001x EV/DO

HSDPA

Expected market share

EDGEEvolution

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UMTS Network Architecture

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

R NS

UTRAN

SIM ME

USIMME

+

PSTN

PLMN

Internet

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FAQs:Why Call congestion problem (Network Busy) occurs?

Congestion is the unavailability of network to the subscriber at the timeof making a call.

Common Reasons:

• Traffic channels (TCH) represent a voice channel and each call usesTCH .

One Radio unit (TRX) can have 8 channels.So One Radio unit (TRX) should handle 8 simultaneous calls.Total 12 TRXs are there in each BTSs.So, total (12X 8) = 96 simultaneous calls can go on.

But 87 out of 96 calls are possible as rests of the channels are used for signaling purpose.

For half rate channels total no of calls will be double i.e 87X2 = 174

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Why Call drop in GSM network occurs?

Common reasons: • Equipment: GSM radios/Combiners can be a cause of this, solution

to this is replacement of the unit. A Mobile Station (phone) can alsobe a cause.

• VSWR (voltage wave standing ratio): VSWR caused by poor connections on feeders, water penetration, fault on antenna etc.

• Transmission problem: If transmission is not perfect, high B.E.R (Bit

error ratio) or other factors causing inaccuracy of transmission. • Interference: when there's frequency interfere .

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Why Call Mute occurs in GSM network?

Common reason:• Interference.

• PCM channel problems.Why Cross Talk occurs? • Same frequency in more than one TRX

in a single site.• TRX fault.

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2G and 3G latching problems

• If handover is not properly defined.

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Thank You