GSM-Global System for Mobile Communication

Presented by:- Pratibha ECE Vth sem

SEMINAR ON

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

GSM:History

• Developed by Group Spéciale Mobile (founded 1982) which was an initiative

of CEPT ( Conference of European Post and Telecommunication )

• Aim : to replace the incompatible analog system

• Presently the responsibility of GSM standardization resides with special mobile

group under ETSI ( European telecommunication Standards Institute )• Full set of specifications phase-I became available in 1990

• Under ETSI, GSM is named as “ Global System for Mobile communication “

• Today many providers all over the world use GSM (more than 135

countries in Asia, Africa, Europe, Australia, America)

• More than 1300 million subscribers in world and 45 million subscriber in India.

Tele Services

• Telecommunication services that enable voice communication via mobile phones• Offered services - Mobile telephony - Emergency calling

Bearer Services

• Include various data services for information transfer between GSM and other networks like PSTN, ISDN etc at rates from 300 to 9600 bps

• Short Message Service (SMS) –up to 160 character alphanumeric data transmission to/from the mobile terminal

• Unified Messaging Services(UMS)• Group 3 fax• Voice mailbox• Electronic mail

Supplementary Services

Call related services :• Call Waiting- Notification of an incoming call while on the handset

• Call Hold- Put a caller on hold to take another call• Call Barring- All calls, outgoing calls, or incoming calls

• Call Forwarding- Calls can be sent to various numbers defined by the user

• Multi Party Call Conferencing - Link multiple calls together

• CLIP – Caller line identification presentation• CLIR – Caller line identification restriction• CUG – Closed user group

System UplinkDownlink

GSM 900 890-915 MHz935-960 MHz

GSM 1800 1710-1785 MHz1805-1880MHz

GSM 1900 1850-1910MHz 1930-1990MHz

GSM is a typical 2nd generation system

GSM Specifications-1

Performance characteristics of GSM

Communication Mobile, wireless communication; support for

voice and data srvices

Total mobility International access, chip-card enables use of

access points of different providers

Worldwide connectivityOne number, the network handles localization

BTS

MSC VLR

HLR

PSTNISDN

DataNetworks

(

Air interface

OMC

BTS

BTS

VLR

BSCBSC

A InterfaceA-bis interface

UM Interface

GSM System Architecture

GSM Applications 1.Mobile telephony

2.Telemetry System - Fleet management - Automatic meter reading - Toll Collection - Remote control and fault reporting of stolen sets

3.Value Added Services

Mobile Station (MS)A Typical Handset Consists

of the following parts:◦ A microscopic microphone◦ A speaker◦ An LCD or plasma display◦ A mini keyboard◦ An Antenna◦ A battery◦ A Circuit board◦ SIM

Mobile station (MS)MS is the radio mobile terminal carried by the

subscriberMS comprises of all user equipment and

software needed for communication with GSM end-point of the radio interface (Um)

MS consists of ◦ User independent HW and SW◦ SIM (Subscriber Identity Module)

MS can be identified by IMEI (Intl Mobile Equipment Identity)

MSs have transmit power of 2W and 1W

SIM

Subscriber Identity Module (SIM)

• Smart card contains the International Mobile Subscriber Identity (IMSI)

• Allows user to send and receive calls and receive other subscribed services

• Encoded network identification details - Key Ki,Kc and A3,A5 and A8 algorithms• Protected by a password or PIN• Can be moved from phone to phone – contains

key information to activate the phone

What is SIM capable of?Display text from the SIM on the Mobile Equipment's display.

Set up a voice or data call to a number held in the SIM

Send an SMS message.

Play a tone in the Mobile's ear-piece or ringer

CONTINUED

Establish an interaction with the user.Provide local information from the ME

to the SIM.Allow help text to be displayed for the

user if requested.Encrypt data being sent via handset

whenever needed.SIM cards were perceived as Security

modules for authentication of user with some extra memory

System ArchitectureBase Station Subsystem (BSS)

Base Transceiver Station (BTS):

• Encodes,encrypts,multiplexes,modulates and feeds the RF signals to the antenna.

• Frequency hopping• Communicates with Mobile station and BSC• Consists of Transceivers (TRX) units

Base Transceiver Station (BTS)

Comprises of all radio specific functions and components including antennas, amplifiers, signal processing (houses all transceivers)

If directed antennas are used, one BTS can cover several cells

Connected to MS via Um interface and to BSC via Abis interface

GSM cell can measure between 100m to 35 kms depending on environment

Some functions of BTS

Ability to manage Full Rate and Half Rate channels.

Supervision of Stationary Wave Report (SWR) on the antenna

Frequency HoppingAntenna DiversityDiscontinuous Transmission (DTX) both in the

Uplink and Downlink

Base Station Controller (BSC)

Governs the radio resources for one or more BTSsControlling connection between the BTSs and

MSCsManaging of network resources, administrating

radio channels, signaling, frequency hopping anad handovers

Mapping of radio channels (Um) onto terrestrial channels (A interface).

Performs paging of MSFunctions of transforming the Full Rate (16 KBPS)

or Half Rate (8 KBPS) radio channels into 64 KBPS channels

Handover Cellular systems require handover procedures, as single

cells do not cover the whole service area, but, e.g., only up to 35 km around each antenna . The smaller the cell size and the faster the movement of a mobile station through the cells (up to 250 km/h for GSM), the more handovers of ongoing calls are required. However, a handover should not cause a cut-off, also called call drop.

There are two basic reasons for a handover (about 40 have been identified in the standard):The mobile station moves out of the range of a BTS or a certain antenna of a BTS respectively. Thus, the received signal level becomes lower continuously until it falls underneath the minimal requirements for communication. Or the error rate may grow due to interference, the distance to the BTS may be too high (max. 35 km) etc. - all these effects may diminish the quality of the radio link and make radio transmission impossible in the near future.

HANDOVER

Cellular systems require Handover procedures

Two basic reasons–MS moves out of the range of a BTS -

Signals becoming weaker– Interference cause errors

What is CDMA?Code Division Multiple Access (CDMA)

◦Digital Wireless Technology

◦Pioneered and commercially developed by QUALCOMM.

CDMA was adopted by the Telecommunications Industry Association (TIA) in 1993.

◦Commercially introduced in 1995

◦May 2001 there were 35 million subscribers on cdmaOne systems worldwide. 

◦As of Dec 2002,There were 127 million CDMA users worldwide.

◦Fastest-growing wireless technologies

◦Provides greater total capacity than other technologies

◦Choice new 3G systems

The original CDMA(IS 95) is now known as CDMAOne. 

We now have cdma2000 and its variants like 1x EV, 1xEV-DO, and 3x.

The refer to variants of usage of a ◦1x uses a 1.25Mhz channel. ◦3X uses a 3.75 Mhz channel

Advantages of CDMA

◦Huge Bandwidth◦Voice clarity◦Less call drops (almost zero) during the peak period

◦Efficient power control methods (even in the handsets)

◦More security

THANKS