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04/2009


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Overview

1. INTRODUCTION TO GSM

2. GSM ARCHITECTURE3. GEOGRAPHICAL NETWORK

ORGANIZATION

4. GSM NUMBERING5. GSM CALLING (MOC, MTC)


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Overview


a. What is GSM

b. GSM services

c. History

d. GSM advantages and disadvantages


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What is GSM? GSM (GlobalSystem for Mobile communication)

is a Worldwide Digital Cellular CommunicationsNetwork formerly: Groupe Spciale Mobile (founded 1982)

used in over 184 countries

The GSM network provides for mobile voice communication international roaming

mobile fax

text messaging

data services


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What is GSM? GSM is a Second Generation (2G) digital radio

cellular network

Time Division Multiplexing / Multiple access(TDM/TDMA) are employed

TDM / TDMA allows: One frequency channel to be subdivided

Multiple conversations over a single physicalchannel


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GSM Subscriber ServicesTwo basic types:

1. Telephony (Teleservices)Mainly voice services providing capability to

communicate with other subscribers

2. Data (Bearer services)

Capacity necessary to transmit appropriate datasignals between two access points creating an

interface to the network


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GSM Subscriber ServicesGSM supports the following subscriber services:

1. Dual tone multi frequency (DTMF)tone signaling scheme used for control purposesE.g. Remote control of an answering machine

2. Facsimile group III

GSM supports CCITT group III Facsimile

Special fax converter forms junction betweenstandard analogue fax and GSM FAX


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GSM Subscriber Services3. Short Message Services (SMS)

Messaging facility consisting of maximum 160

alphanumeric characters to or from a mobi

lestation to another

4. Cell Broadcast

Variation of SMS where maximum number ofalphanumeric characters is 93

Can be broadcast to users in a certaingeographical area.

E.g. Traffic congestion warnings


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GSM Subscriber Services5. Voice Mail

Answering machine within the network controlled by thesubscriber

Security code needed to access

6. Fax MailSubscriber can receive fax messages at any fax machine

7. Emergency numbercommon number

mandatory for all service providersfree of chargeconnection with the highest priority (pre-emption of other

connections possible)


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GSM Supplementary Services GSM supports comprehensive list of supplementary

services supporting both data and voice services

The following compromises a partiallist:

1. Call forwarding

2. Barring of outgoing calls

3. Advice of charge (AoC)


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GSM Supplementary Services4. Call hold

5. Call waiting

6. Multiparty service

7. Calling line identification presentation / restriction

8. Closed user groups (CUGs)


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Multiple incompatible networks Before GSM, the technical incompatibilities

between networks were due to: operation on different radio frequencies use of incompatible signals to control the call setup,

handoff and end of the connection.

Even when the same technological standardexisted between countries: there were usually organisational barriers

pricing / charging schemes were incompatible


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Analogue NetworksAn analogue cellular system:

uses frequency modulation (FM) to send data and

signals Divides the spectrum only into physical channels

of different frequency

Does not offer added services such as Caller ID or

Messaging


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1stGeneration Analogue

Networks

Japan1978/88NTT/NTT Hi Cap

Japan1991NTACS/JTACS

UK, Ireland, Spain1985TACSIta

l

y198

5RTMS

France1985RadioCom

Scandinavia + 30 other countries1981/86NMT450/900

UK,1987ETACS

Germany, Austria, Portugal, South

Africa

1981C-Netz

USA, Australia1983AMPS


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How did GSM get established CEPT formed a technical study group named

Groupe Spcial Mobile.

The groups mandate was to: formulate a specification for a pan-European

mobile cellular radio system in 900MHz band

Tackle the associated technical, economic andlogistical problems.


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Objectives of GSM To provide a European second

generation digital network standard

Increase the market for EquipmentManufacturers

Allow Manufacturing to establisheconomy of scale.


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Development Timeline 1985 Digital Coded Speech over radio link

chosen as basis for GSM

1986 Validation Trials held in Paris

1988 Following successful validation

multiple invitations to tender issued

1992 Commercial Networks Launched


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First portable units First portable units

were really big and

heavy. Called

transportables orluggables.


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Curt The Hotline Pocket The first Ericsson

Handheld introduced

in 1987 Adapted from a

police radio designfirstly into a NMT-900 compatible unit.

Later adapted forthe ETACS network.


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Olivia - Hotline Introduced in 1989

Originally introduced

in 1989 for the NMT-900, ETACS and

AMPS networks

Later adapted for

GSM, and is the firstEricsson GSMphone.

First all digital

mobile


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Sandra First introduced by

Ericsson in 1991

First version used inNMT-900 networks,followed by versionfor ETACS, D-

AMPS/AMPS

Adapted for GSM in1993


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Jane Introduced by

Ericsson in 1996

Several versionmanufactured for

AMPS, GSM, DCS,PCD1900/GSM


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GSM Specification

Channel coding, Interleaving, Frequency hopping, Adaptive

equalization

Diversity

Regular Pulse Excitation - Long Term Prediction (RPE-LPC)13kbit/s

Speech coder

Time Division Multiple Access (TDMA) (narrow band)Access Method

270 kbit/sTransmission rate

Gaussian Minimum Shift Keying (GMSK)Modulation

200 kHzCarrier Separation

45MHz /95MHzDuplex distance

Uplink: 890 MHz 915 MHz / 1710 MHz 1785 MHz

Downlink: 935 MHz 960 MHz / 1805 MHz 1880 MHz

Frequency Band


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GSM compared to 1G Systems Communication

mobile, wireless communication; support for voice and data services

Total mobility

international

access, chip-card enabl

es use of access points of different providers

Worldwide connectivity one number, the network handles localization

High capacity if needed better frequency efficiency, smaller cells, more customers per cell

High transmission quality high audio quality and reliability for wireless, uninterrupted phone calls at higher

speeds (e.g., from cars, trains)

Security functions access control, authentication via chip-card and PIN


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What are some of disadvantages

of GSM?There is no perfect system!!

no end-to-end encryption of user data reduced concentration while driving

electromagnetic radiation

abuse of private data possible

roaming profiles accessible

high complexity of the system

several incompatibilities within the GSM standards


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What are the trends with mobile

phone subscribers worldwide?


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Development of mobile

telecommunication systems


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Overview



ORGANIZATION



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Overview


2. GSM ARCHITECTUREa. Components

b. Interfaces


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Components


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ComponentsGSM is a PLMN (Public Land Mobile Network)

RSS (Radio Subsystem): covers all radio aspects BSS (Base Station Subsystem): BSC, BTSs MS (Mobile Station)

NSS (Networkand Switching Subsystem): call forwarding,handover, switching MSC (Mobile Switching Center) HLR (Home Location Register) VLR (Visitor Location Register)

OSS (Operation Subsystem): management of the network OMC (Operation and Maintenance Center) AuC (Authentication Center) EIR (Equipment Identity Register)


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Components

PLMN : Publ

ic Land Mobil

e Network

BSC : Base Station ControllerBTS : Base Transceiver StationMS : Mobile Station


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Radio Subsystem


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Radio Subsystem


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Components

PLMN : Publ

ic Land Mobil

e Network

ISC : International Switching CenterMSC : Mobile Switching CenterGMSC : Gateway Mobile Switching CenterHLR : Home Location Register VLR : Visitor Location Register


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Network and Switching

SubsystemNSS is the main component of the public mobile

network GSM switching, mobility management, interconnection to other networks, system

control

What are the components of the NSS? Mobile Services Switching Center (MSC)

controls all connections via a separated network to/from a mobile terminal within thedomain of the MSC - several BSC can belong to a MSC

Home LocationRegister (HLR) central master database containing user data, permanent and semi-permanent data of

all subscribers assigned to the HLR (one provider can have several HLRs)

Visitor LocationRegister (VLR) local database for a subset of user data, including data about all user currently in the

domain of the VLR


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Network and Switching

Subsystem


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ComponentsAuC : Authentication Center

EIR : Equipment Identity Register

OMC : Operation and Maintenance Center

PLMN : Public Land Mobile Network


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Operation SubsystemThe OSS (Operation Subsystem) enables centralized operation,

management, and maintenance of all GSM subsystems Components

Authentication Center (AuC) generates user specific authentication parameters on request of a VLR authentication parameters used for authentication of mobile terminals and

encryption of user data on the air interface within the GSM system

Equipment Identity Register (EIR) registers GSM mobile stations and user rights stolen or malfunctioning mobile stations can be locked and sometimes

even localized

Operationand Maintenance Center (OMC) different control capabilities for the radio subsystem and the network

subsystem


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Network Databases


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Summary


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Interfaces


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Interfaces


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Interfaces


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Interfaces


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Overview



ORGANIZATION



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Geographical network

organization


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MSC regionThe International GSM/DCS system area comprises all countries where PLMNis implementedWithin these countries, the PLMN are further subdivided into MSC areas


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Location area (LA)The MSC service areas, in turn, consists of cells which are organized as Location

Areas (LA)Allows MS to move freely without updating location informationSystem uses LAs to locate a MS using broadcast messages.


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Overview



ORGANIZATION



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GSM numbering


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Permanent subscriber numbering


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MSRN & TMSI


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IMEI, LAI & CI


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Summary


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Overview



ORGANIZATION



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Overview1. INTRODUCTION TO GSM2. GSM ARCHITECTURE3. GEOGRAPHICAL NETWORK

ORGANIZATION4. GSM NUMBERING

5. GSM CALLING (MOC, MTC)a. MOC (Mobile Originated Call)b. MTC (Mobile Terminated Call)


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Mobile Originated Ca

ll

1, 2: connectionrequest

3, 4: security check

5-8: check resources(free circuit)

9-10: set up call


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Mobile Originated Ca

ll


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Mobile Terminated Ca

ll

1: calling a GSM subscriber 2: forwarding call to GMSC 3: signal call setup to HLR 4, 5: request MSRN from VLR 6: forward responsible MSC to

GMSC 7: forward call to current MSC 8, 9: get current status of MS 10, 11: paging of MS 12, 13: MS answers 14, 15: security checks 16, 17: set up connection


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Mobile Terminated Ca

ll


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DetailSequence of MTC


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Future mobile

telecommunication networks


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