GSM Presentation Nirma 25 August 2007

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Global System forMobile Communication

Presented By:Deepika SharmaDept.Of Computer Engg.



Topics CoveredGSM Introduction

GSM Network Architecture

GSM BasicsChannelisation MethodsMultiple Access Methods





GSM

Global S ystem for Mobile communication

Also called Global S tandard for Mobile communication

Standard defined by ETSI ( European TelecommunicationsS tandards Institute)



What does GSM Offer?

Voice with better QualityServices (PIN, Call barring, Call forwarding, Calltransfer, Call waiting, Call Holding, Closed UserGroup)Value added services (SMS, MMS, Caller Tune etc)And of course - Mobility







BTS 3

BTS 2

BTS 1

BSC

PSTN N/W

HLR

VLR

AUC

EIR

SMSC

VMSC

MSC

OSS

NSS

BSSMS



Mobile Station (MS)

Mobile S tation (MS) consist of two unitsMobile Hand set SIM - S ubscriber Identity Module

- Provides user an access to theNetwork.

- Each handset has unique identity no.

called IMEI ( International Mobile EquipmentIdentity)

- SIM is a removable module fits inside the Mobilehandset.

- Each SIM has unique number calledIMSI (International Mobile S ubscriber Identity).

- Also it stores Network specific information likeAuthentication Key (Ki), Local Area Identity (LAI).

- The SIM also stores other carrier specific data such as

SMSC ( S hort Message S ervice Centre) number,S ervice

P rovider Name (SPN), Value Added S ervice (VAS)applications.

- It contains the ROM of 6 to 16KB, RAM of 128 to256 bytes and EEPROM of 3 to 8KB.



BTS has a set of Transceivers to talk to MS.

One BTS covers one or more than one cell.

Capacity of BTS depends on no of Transceivers.

BTS is connected to BSC via A’bis interface.

Transmission rate on A’bis is 2 Mbps.

Interface between MS & BTS is called Air I/f.

Speech Transmission rate on Air I/f is 13 Kbps.

BTS controls RF parameters of MS.

Each Transceiver has 8 TDMA channels to carry Voice & signalling.

Base Transceiver Station (BTS)

BTSAntenna

Arrangement



Base Station Controller (BSC)

BSCBSC controls several BTSs.BSC manages channel allocation, Power Control of MS/BTS

& Handover of calls from one BTS to another BTS.

BSC is connected to MSC via A interface.

Transmission rate on A I/f is 2 Mbps.

Interface between BSC & BTS is called A’bis I/f.

BSC has database for all of its BTS’s parameters.

BSC provides path from MS to MSC.



Mobile Switching Centre (MSC)

MSC manages all call related functions andBilling/Charging related information.

MSC is connected to HLR & VLR for subscriberidentification & routing incoming calls.

MSC capacity is in terms of no of subscribers.

MSC is connected to BSC at one end and with different

network on other end.

Call Detail Record (CDR) is generated for each & every

call in the MSC. MSC



Visiting Location Register (VLR)

VLR

MSC

Active Subscriber is registered in VLR.

It has temporary data base of all the active subscribers used for their callrouting.

HLR validates subscriber before registration.

MSC ask VLR before routing incoming call.



Home Location Register (HLR)

HLR

MSC

All Subscribers data is stored in HLR.

It has permanent data base of all the registered subscribers.

HLR has series of numbers for all subscribers.



Authentication Centre (AUC)

HLR

MSC

Authentication is a process to verify the subscriber SIM.

Secret data & verification algorithm are stored in to the AUC.

AUC & HLR combined to authenticate the subscribers.

Subscriber authentication can be done on every call, if required.

AUC



Equipment Identity Register (EIR)

EIR

MSC

All subscriber's mobile handset data is stored in EIR.

MSC asks mobile to send it IMEI & then checks it with data available in EIR.

EIR has different classification for mobile handsets like, White list,

Grey list & Black list.

According to category the MS can make calls or can be stopped from

making calls.



Operation & Maintenance Centre (OMC)

OMCAll the network elements are connected to OMC.

OMC monitors health of all network elements &carry out maintenance operation, if required.

OMC link to BTSs are via parent BSC.

OMC keeps records of all the faults occurred.

OMC can also do Traffic analysis.

OMC may prepares MIS Report for the network.

VMSC & SMSC



VMSC & SMSC

MSC

SMSC VMSC

Voice Mail Service Centre : To provide Voice Mail service.It has database for all the VMS subscribers & also stores voicemessages for them.

Short Message Service Centre : To provide text message service.

To send short messages from mobile to another mobile subscriber.Messages can also be sent by Manual Terminal connected to SMSC.



GSMBASICS

Ch li ti



Channelization

Channelisation can be done primarily by threemethods:

FDMA (Frequency Division Multiple Access)TDMA (Time Division Multiple Access)CDMA (Code Division Multiple Access)

FDMA



FDMA

Frequency

Time

Power

Television Channels (Star, Zee, Sony,..)

TDMA



TDMA

GSM has 8 timeslots on each 200 KHz channel

Frequency

Time

Power

Duplex Access Methods



Duplex Access Methods

F1 F2 Frequency

Amplitude

Time

Tx Rx

Frequency Division Duplex (FDD)Transmit on one frequency and receive on another frequency

Time Division Duplex



Time Division Duplex

Time Division DuplexTx and Rx is on the same frequency but on different times

E.g.. Walky Talky

F1 Frequency

Amplitude

Time

Tx

Rx



GSMAir Interface

GSM Air Interface



GSM Air Interface

Separate Bands for Uplink and Downlink

Downlink : 935- 960 MHzUplink : 890- 915 MHz



Documents

GSM Presentation Nirma 25 August 2007