Presentation on GSMNetwork

What is GSM ???

Global System for Mobile (GSM) is a second generation cellular standard developed to cater voice services and data delivery using digital modulation

HISTORY

Early 1980s there was analog technologies: Advanced Mobile Phone Services(AMPS)in

North America. Total Access Communications

System(TACS)

in the UK. Nordic Mobile Telephone(NMT) in Nordic

countries.

During 1990 many digital mobile standards were introduced in different regions/ countriesDAMPS ( Digital Advance Mobile Phone

Service)GSM ( Global System for Mobile

Communications)CDMA ( Code Division Multiple Access )These are known as 2nd Generation System

GSM in India

Figures: March 2005

Bharti27%

BSNL22%

Spice 4%

IDEA13%

Hutch19%

BPL6%

Aircel4%

Reliance3%

MTNL2%

Bharti

BSNL

Hutch

IDEA

BPL

Aircel

Spice

Reliance

MTNL

GSM Specifications-1

RF SpectrumGSM 900

Mobile to BTS (uplink): 890-915 MHz BTS to Mobile(downlink):935-960 MHz Bandwidth : 2* 25 MHz

GSM 1800 Mobile to BTS (uplink): 1710-1785 MHz BTS to Mobile(downlink) 1805-1880 MHz Bandwidth : 2* 75 MHz

GSM Specification-II

Carrier Separation : 200 KHzDuplex Distance : 45 MHzNo. of RF carriers : 124Access Method : TDMA/FDMAModulation Method : GMSKModulation data rate : 270.833 Kbps

GSM Services

Tele-services – Telecommunication services that enables voice communication via mobile phones.

Bearer or Data Services- include various data services for data transfer,SMS,electronic mail.

Supplementary services- call related services.

GSM Cell Structure

The power level of a

transmitter within a

single cell must be

limited to reduce the

interference with the

neighbouring cells.

Neighbouring cells

cannot share the

same channels Different size of

patterns: 4,7,12 or 21

cells in one cluster

GSM Architecture

GSM Broad parts

Base Station

Subsystem(BSS)

= BTS + BSC

BTS

Base Transceiver Station (BTS) serves a single cell usually placed in the centre of a cellcoding encrypting multiplexing modulatingsynchronizing

Base Station Controller(BSC) Manages Radio resources for BTS Assigns Frequency and time slots for all MS’s in its

area Handles call set up Handover for each MS Radio Power control It communicates with MSC and BTS

The Transcoder and adaptation unit(TRAU) (13Kbps speech or data+ 3Kbps additional synchronizing data)*4

=64Kbps (TRAU

Standard rate)

Mobile Switching Centre(MSC)

The central component of the Network Subsystem

(30 + 2)* 64Kbps = 2,048Mbps(E1) or better to the other network interfaces(PSDN,ISDN)

Billing Location registration Gateway to SMS Synchronizing BSSHandover management

The Registers Completing theNSS

Home Location Register (HLR) contains all

information of each subscriber registered in the corresponding GSM network

Visitor location Register (VLR) contains selected information from the HLR, which is necessary for call control and provision of the subscribed services, for each mobile currently located in the

geographical area controlled by the VLR NSS = HLR + VLR + MSC

Equipment Identity Register (EIR) contains a list of all valid mobile equipment on the network

Authentication Centre (AUC) stores a copy of the secret key stored in each subscribers

SIM cardEIR and AUC are used for security and

authentication purposes

Call Routing

Call Originating from MSCall termination to MS

Outgoing Call

1. MS sends dialled number to BSS

2. BSS sends dialled number to MSC

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

4 MSC routes the call to GMSC5 GMSC routes the call to local

exchange of called user6 Answer back(ring back) tone is

routed from called user to MS via GMSC,MSC,BSS

Incoming Call1. Calling a GSM

subscribers2. Forwarding call to

GSMC3. Signal Setup to HLR4. Request MSRN from

VLR5. Forward responsible

MSC to GMSC6. Forward Call to

current MSC7. Get current status of

MS 8. Paging of MS 9. MS answers10. Security checks11. Set up connection

Security in GSM

On air interface, GSM uses encryption and TMSI instead of IMSI.

SIM is provided 4-8 digit PIN to validate the ownership of SIM

3 algorithms are specified :

- A3 algorithm for authentication

- A5 algorithm for encryption

- A8 algorithm for key generation

Advantages of GSM over Analog system

Capacity increasesReduced RF transmission power and longer battery

life. International roaming capability.Better security against fraud (through terminal

validation and user authentication).Encryption capability for information security and

privacy.Compatibility with ISDN,leading to wider range of

services

Generation After GSM 2nd Generation

GSM -9.6 Kbps (data rate)

2.5 Generation ( Future of GSM)HSCSD (High Speed ckt Switched data)

Data rate : 76.8 Kbps (9.6 x 8 kbps)GPRS (General Packet Radio service)

Data rate: 14.4 - 115.2 KbpsEDGE (Enhanced data rate for GSM Evolution)

Data rate: 547.2 Kbps (max) 3 Generation

WCDMA(Wide band CDMA)Data rate : 0.348 – 2.0 Mbps

Thank you !!!