Gsm Basics 2

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GSMGLOBAL SYSTEM FOR

MOBILE COMMUNICATION


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DISCUSSION TOPICS

History

Building Blocks

System Architecture

Features (Basic and Advanced)

Advantages of GSM

Futurewhats next


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HISTORY

Early 80s Europe was experiencing rapid growth

in the analog cellular telephone systems

1982 Conference of European Posts and

Telegraphs (CEPT) GSM (Groupe Special Mobile)group was formed to study and develop a pan-

European public land mobile system

GSM mandate was to develop a standard to becommon for the countries that created itprovide

service to the entire European continent


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HISTORYcontd.

GSM criteria

Good subjective speech quality

Low terminal and service cost

Support for international roamingone system for all of Europe Ability to support handheld terminals

Support for range of new services and facilities

Enhanced Features

ISDN compatibility Enhance privacy

Security against fraud


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HISTORYcontd.

Late 1980s GSM work was transferred to theEuropean Telecommunication Standards Institute(ETSI) and SGM (Special Mobile Group) was

created

Document the functionality and interaction of everyaspect of the GSM network

1987 ETSI oversees the creation of GSM MoU(Memorandum of Understanding) Association


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HISTORYcontd.

Formal objective of the GSM MoU Association is thepromotion and evolution of the GSM systems and GSMplatforms

Concepts of a published international standard and aconstantly evolving common standard are unique to GSM

Work groups throughout the world specifically designed toallow interested parties to meet and work on findingsolutions to systems enhancements that will fit intoexisting programs of GSM operators


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HISTORYcontd.

Phase I of GSM specifications was published in 1990

International demand was so great that the system namewas changed from Groupe Special Mobile to GlobalSystems for Mobile Communications (still GSM)

Commercial service started in mid-1991 1992 first paying customers were signed up for service

By 1993 there were 36 GSM networks in 22 countries

Early 1994 there were 1.3 million subscribers worldwide

By 1996 there were more than 25 million subscribersworldwide

By October 1997 it had grown to more than 55 millionsubscribers worldwide


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Global System for Mobile (GSM) is a second

generation cellular standard developed to cater

voice services and data delivery using digital

modulation

What is GSM ?


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GSM in World

Figures: March, 2005

37%

1% 4%43%

4%

3%

3%

3% (INDIA)

3%

Arab WorldAsia Pacific

Africa

East Central AsiaEurope

Russia

IndiaNorth America

South America


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GSM in India

Figures: March 2005

Bharti

27%

BSNL

22%

Spice

4%

IDEA

13%

Hutch

19%

BPL6%

Aircel

4%

Reliance

3%MTNL

2%

Bharti

BSNL

Hutch

IDEA

BPL

Aircel

Spice

Reliance

MTNL


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Building Blocks

AMPSAdvanced Mobile Phone System

TACSTotal Access Communication System

NMTNordic Mobile Telephone System


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Building Blockscontd.

AMPSAdvanced Mobile Phone System

analog technology

used in North and South America andapproximately 35 other countries

operates in the 800 MHz band using FDMAtechnology


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TACSTotal Access Communication System

variant of AMPS

deployed in a number of countries

primarily in the UK


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NMTNordic Mobile Telephone System

analog technology

deployed in the Benelux countries and Russia

operates in the 450 and 900 MHz band

first technology to offer international roamingonly withinthe Nordic countries


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System Architecture

Mobile Station (MS)Mobile Equipment (ME)

Subscriber Identity Module (SIM)

Base Station Subsystem (BBS)Base Transceiver Station (BTS)

Base Station Controller (BSC)

Network SubsystemMobile Switching Center (MSC)

Home Location Register (HLR)Visitor Location Register (VLR)

Authentication Center (AUC)

Equipment Identity Register (EIR)

S t A hit t


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System Architecture

Mobile Station (MS)

The Mobile Station is made up of two entities:

1. Mobile Equipment (ME)

2. Subscriber Identity Module (SIM)


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Mobile Station (MS)

The Mobile Station consists of the Mobile Equipment (ME)and the Subscriber Identity Module (SIM).

Mobile Equipment

The Mobile Equipment is the hardware used by the

subscriber to access the network.

The mobile equipment can be Vehicle mounted, with the

antenna physically mounted on the outside of the vehicle

or portable mobile unit, which can be handheld.

Mobiles are classified into five classes according to their

power rating.

System Architecture


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System Architecture

Mobile Station (MS) contd.

Subscriber Identity Module (SIM)

Smart card containing the International MobileSubscriber Identity (IMSI)

Allows user to send and receive calls and receive othersubscribed services

Encoded network identification details

Protected by a password or PIN

Can be moved from phone to phonecontains keyinformation to activate the phone


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SIM The SIM is a removable card that plugs into the ME.

It identifies the mobile subscriber and provides information

about the service that the subscriber should receive. The SIM contains several pieces of information

Internat ional Mob i le Subsc r ibers Ident i ty ( IMSI ) - This n umber id ent i f iesthe mobi le subscr iber. I t is only transmit ted over the air dur ing

init ial iz ing.

Temporary Mobi le Subscr iber Ident i ty ( TMSI ) - This number also

ident i f ies the sub scr ib er. It can be alternatively used by the sys tem. It is

per iodical ly changed by the system to p rotect the sub scr iber f rom being

ident i fied by someone at tempt ingng to m oni tor th e radio in ter face.

Locat ion Area Ident i ty ( LA I ) - Ident i f ies the current locat ion of th esubscr iber.

Subsc r ibers Au thent icat ion K ey ( Ki ) - This is us ed to authent icate theSIM card .

Mob ile Station Internation al Stand ard Data Number ( MSISDN ) - This isthe telepho ne num ber of the mobi le.


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SIM

Most of the data contained within the SIM is protected againstreading (eg Ki ) or alterations after the SIM is issued.

Some of the parameters ( eg. LAI ) will be continously updatedto reflect the current location of the subscriber.

The SIM card can be protected by use of Personal Identity

Number ( PIN ) password. The SIM is capable of storing additional information such as

accumulated call charges.

G S M

FULL SIZE SIM CARD

MINI SIM CARD


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Mobile Station International Subscribers DialingNumber ( MSISDN ) :

Human identity used to call a MS

The Mobile Subscriber ISDN (MSISDN) number is thetelephone number of the MS.

This is the number a calling party dials to reach thesubscriber.

It is used by the land network to route calls toward theMSC.

98 XXX 12345

CC

NDC

SN

CC NDC SN

= Country code

= National Destination Code

= Subscriber Number


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Internat ional Mob ile Sub sc ribers Iden ti ty ( IMSI )

:

Network Identity Unique to a MS The International Mobile Subscriber Identity (IMSI) is the

primary identity of the subscriber within the mobile network

and is permanently assigned to that subscriber.

The IMSI can be maximum of 15 digits.

MCC MNC MSIN

404 XX 12345..10

MCCMNC

MSIN

= Mobile Country Code ( 3 Digits )= Mobile Network Code ( 2 Digits )

= Mobile Subscriber Identity Number


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Tempo rary Mob ile Subsc ribers Identi t y ( TMSI ) :

The GSM system can also assign a Temporary Mobile

Subscriber Identity (TMSI).

After the subscriber's IMSI has been initialized on the system,

the TMSI can be used for sending messages backwards and

forwards across the network to identify the subscriber.

The system automatically changes the TMSI at regular

intervals, thus protecting the subscriber from being identifiedby someone attempting to monitor the radio channels.

The TMSI is a local number and is always allocated by the

VLR.

Equ ipment Identi ty Reg ister ( EIR )


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Equ ipment Identi ty Reg ister ( EIR )

The Equipment Identity Register (EIR) contains a centralizeddatabase for validating the international mobile stationequipment identity, the IMEI.

The database contains three lists: The whi te l is t con ta ins the numb er series o f equipm ent ident i ties th at

have been al located in the dif ferent p art ic ipating cou ntr ies. This l is t

does not conta in indiv idual numbers but a range of numbers by

ident i fy ing the beginning and end of the ser ies .

The grey lis t contains IMEIs of equipm ent to be mon itored and observedfor locat ion and correct funct ion.

The black l is t contains IMEIs of MSs wh ich h ave been reported stolen o rare to be denied s ervice.

The EIR database is remotely accessed by the MSCs in theNetwork and can also be accessed by an MSC in a differentPLMN..


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Equipment Identity Register ( EIR )

White List

All Valid

assigned IDs

Range 1

Range 2

Range n

Black List

Service denied

MS IMEI 1

MS IMEI 2

MS IMEI n

Grey List

Service allowedbut noted

MS IMEI 1

MS IMEI 2

MS IMEI n

EIR

B St ti Id tit C d


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BSIC allows a mobile station to distinguish between

neighboring base stations.

It is made up of 8 bits.

NCC = National Colour Code( Differs from operator to operator

BCC = Base Station Colour Code, identifies the base station to

help distinguish between Cells using the same BCCH

frequencies

Base Station Identity Code

BCC00 BCCNCC

7 6 5 4 3 2 1 0

System Architecture


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System Architecture

Base Station Subsystem (BSS)

Base Station Subsystem is composed of two parts

that communicate across the standardized Abis

interface allowing operation between components

made by different suppliers

1. Base Transceiver Station (BTS)

2. Base Station Controller (BSC)

System Architecture


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System Architecture

Base Station Subsystem (BSS) contd.

Base Transceiver Station (BTS)

Houses the radio transceivers that define a cell

Handles radio-link protocols with the Mobile Station Speech and data transmissions from the MS are

recoded

Requirements for BTS:

reliability

portability

minimum costs


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System Architecture


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y

Network Subsystem

Mobile Switching Center (MSC)

Switch speech and data connections between:Base Station Controllers

Mobile Switching Centers

GSM-networks

Other external networks

Heart of the network

Three main jobs:

1) connects calls from sender to receiver2) collects details of the calls made and received

3) supervises operation of the rest of the network components

System Architecture


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Network Subsystem contd.

Home Location Registers (HLR)- contains administrative information of each subscriber

- current location of the mobile

Visitor Location Registers (VLR)- contains selected administrative information from the HLR

- authenticates the user

- tracks which customers have the phone on and ready to

receive a call

- periodically updates the database on which phones are

turned on and ready to receive calls

System Architecture


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Network Subsystem contd.

Authentication Center (AUC)- mainly used for security

- data storage location and functional part of the network

- Ki is the primary element

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 Listand the Gray List

- Optional database

System Architecture


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y


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INTERFACE NAMES

Each interface specified in GSM has a name

associated with it.NAME INTERFACE

Um MS ----- BTS

Abis BTS ----- BSC

A MSC ------ BSC

B MSC ------VLR

C MSC ----- HLR

D VLR ----- HLR

E MSC ---- MSC

F MSC ------ EIR

G VLR ------ VLR

H HLR ----- AUC

CHANNEL CONCEPT


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Physical channel - Each timeslot on a carrier is referred to as a physical

channel. Per carrier there are 8 physical channels.

Logical channel- Variety of information is transmitted between the MS and

BTS. There are different logical channels depending on the information

sent. The logical channels are of two types

Traffic channel

Control channel

Downlink

Uplink

CHANNELS

CHANNEL CONCEPT

CHANNEL CONCEPT


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GSM Traffic Channels

Traffic Channels

TCH/FFull rate 22.8kbits/s

TCH/HHalf rate 11.4 kbits/s

CHANNEL CONCEPT

CHANNEL CONCEPT


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GSM Control Channels

BCH ( Broadcast channels)

Downlink only

Control Channels

DCCH(Dedicated Channels)

Downlink & Uplink

CCCH(Common Control Chan)

Downlink & Uplink

Synch.Channels

RACHRandom

Access Channel

CBCHCell Broadcast

Channel

SDCCHStandalonededicated

control channel

ACCHAssociated

Control Channels

SACCHSlow associatedControl Channel

FACCHFast AssociatedControl Channel

PCH/AGCH

Paging/Access grant

FCCHFrequency

Correction channel

SCHSynchronization

channel

BCCHBroadcast

control channel

CHANNEL CONCEPT

CHANNEL CONCEPT


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BCH Channels

BCCH( Broadcast Control Channel )

Downlink only

Broadcasts general information of the serving cell called System

Information

BCCH is transmitted on timeslot zero of BCCH carrier

Read only by idle mobile at least once every 30 sec.

SCH( Synchronization Channel )

Downlink only

Carries information for frame synchronization. Contains TDMA

frame number and BSIC.

FCCH( Frequency Correction Channel ) Downlink only.

Enables MS to synchronies to the frequency.

Also helps mobiles of the n cells to locate TS 0 of BCCH carrier.

CHANNEL CONCEPT

CHANNEL CONCEPT


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CCCH Channels

RACH( Random Access Channel )

Uplink only Used by the MS to access the Network.

AGCH( Access Grant Channel )

Downlink only

Used by the network to assign a signaling channel upon

successful decoding of access bursts.

PCH( Paging Channel )

Downlink only.

Used by the Network to contact the MS.

CHANNEL CONCEPT

CHANNEL CONCEPT


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DCCH Channels

SDCCH( Standalone Dedicated Control Channel )

Uplink and Downlink Used for call setup, location update and SMS.

SACCH( Slow Associated Control Channel )

Used on Uplink and Downlink only in dedicated mode.

Uplink SACCH messages - Measurement reports.

Downlink SACCH messages - control info.

FACCH( Fast Associated Control Channel )

Uplink and Downlink.

Associated with TCH only.

Is used to send fast messages like handover messages.

Works by stealing traffic bursts.

CHANNEL CONCEPT

Basic Features Provided by GSM


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Basic Features Provided by GSM

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

Advanced Features Provided by

GSM


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GSM

Calling Line ID- incoming telephone number displayed

Alternate Line Service- one for personal calls

- one for business calls

Closed User Group- call by dialing last for numbers

Advice of Charge- tally of actual costs of phone calls

Fax & Data- Virtual Office / Professional Office

Roaming- services and features can follow customer from market to market

Future -- UMTS (Universal Mobile

T l h S t


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Telephone System

Reasons for innovations- new service requirements

- availability of new radio bands

User demands- seamless Internet-Intranet access

- wide range of available services

- compact, lightweight and affordable terminals

- simple terminal operation

- open, understandable pricing structures for the whole spectrum ofavailable services

Advantages of GSM


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Advantages of GSM

Crisper, cleaner quieter calls Security against fraud and eavesdropping

International roaming capability in over 100 countries

Improved battery life

Efficient network design for less expensive system expansion Efficient use of spectrum

Advanced features such as short messaging and caller ID

A wide variety of handsets and accessories

High stability mobile fax and data at up to 9600 baud

Ease of use with over the air activation, and all account informationis held in a smart card which can be moved from handset tohandset

Gsm Basics 2

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