04/2009. Overview 1. INTRODUCTION TO GSM 2. GSM ARCHITECTURE 3. GEOGRAPHICAL NETWORK ORGANIZATION 4....

04/2009

Overview

1. INTRODUCTION TO GSM2. GSM ARCHITECTURE3. GEOGRAPHICAL NETWORK

ORGANIZATION4. GSM NUMBERING5. GSM CALLING (MOC, MTC)

Overview

1. INTRODUCTION TO GSMa. What is GSMb. GSM servicesc. Historyd. GSM advantages and

disadvantages

What is GSM? GSM (Global System for Mobile

communication) is a Worldwide Digital Cellular Communications Network

formerly: Groupe Spéciale Mobile (founded 1982) used in over 184 countries

The GSM network provides for mobile voice communication international roaming mobile fax text messaging data services

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 physical

channel

GSM Subscriber Services

Two basic types:

1. Telephony (Teleservices)Mainly voice services providing capability to communicate with other subscribers2. Data (Bearer services)Capacity necessary to transmit appropriate data signals between two access points creating an interface to the network

GSM Subscriber ServicesGSM supports the following subscriber services:

1. Dual tone multi frequency (DTMF)tone signaling scheme used for control

purposes E.g. Remote control of an answering machine

2. Facsimile group IIIGSM supports CCITT group III FacsimileSpecial fax converter forms junction

between standard analogue fax and GSM FAX

GSM Subscriber Services3. Short Message Services (SMS)Messaging facility consisting of maximum 160 alphanumeric characters to or from a mobile station to another

4. Cell BroadcastVariation of SMS where maximum number of alphanumeric characters is 93Can be broadcast to users in a certain geographical area. E.g. Traffic congestion warnings

GSM Subscriber Services5. Voice Mail

Answering machine within the network controlled by the subscriber

Security code needed to access

6. Fax MailSubscriber can receive fax messages at any fax

machine

7. Emergency numbercommon numbermandatory for all service providersfree of chargeconnection with the highest priority (pre-emption of

other connections possible)

GSM Supplementary Services

GSM supports comprehensive list of supplementary services supporting both data and voice services

The following compromises a partial list:

1. Call forwarding

2. Barring of outgoing calls

3. Advice of charge (AoC)

GSM Supplementary Services

4. Call hold

5. Call waiting

6. Multiparty service

7. Calling line identification presentation / restriction

8. Closed user groups (CUGs)

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 standard existed between countries: there were usually organisational barriers pricing / charging schemes were incompatible

Analogue Networks

An 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

1st Generation Analogue Networks

Japan1978/88NTT/NTT Hi Cap

Japan1991NTACS/JTACS

UK, Ireland, Spain1985TACS

Italy1985RTMS

France1985RadioCom

Scandinavia + 30 other countries1981/86NMT450/900

UK, 1987ETACS

Germany, Austria, Portugal, South Africa

1981C-Netz

USA, Australia1983AMPS

How did GSM get established CEPT formed a technical study group

named Groupe Spécial Mobile.

The group’s mandate was to: formulate a specification for a pan-European

mobile cellular radio system in 900MHz band

Tackle the associated technical, economic and logistical problems.

Objectives of GSM To provide a European “second

generation” digital network standard

Increase the market for Equipment Manufacturers

Allow Manufacturing to establish economy of scale.

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

First portable units First portable

units were really big and heavy.

Called transportables or “luggables”.

“Curt” – The Hotline Pocket The first Ericsson

Handheld introduced in 1987

Adapted from a police radio design firstly into a NMT-900 compatible unit.

Later adapted for the ETACS network.

“Olivia” - Hotline Introduced in 1989 Originally introduced

in 1989 for the NMT-900, ETACS and AMPS networks

Later adapted for GSM, and is the first Ericsson GSM phone.

First all digital mobile

“Sandra” First introduced by

Ericsson in 1991 First version used

in NMT-900 networks, followed by version for ETACS, D-AMPS/AMPS

Adapted for GSM in 1993

“Jane” Introduced by

Ericsson in 1996 Several version

manufactured for AMPS, GSM, DCS, PCD1900/GSM

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 MHzDownlink: 935 MHz – 960 MHz / 1805 MHz – 1880 MHz

Frequency Band

GSM compared to 1G Systems Communication

mobile, wireless communication; support for voice and data services

Total mobility international access, chip-card enables 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

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

What are the trends with mobile phone subscribers worldwide?

Development of mobile telecommunication systems

Overview



Overview

1. INTRODUCTION TO GSM2. GSM ARCHITECTURE

a. Componentsb. Interfaces

Components

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 (Network and 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)

Components

PLMN : Public Land Mobile Network

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

Radio Subsystem

Components


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

Network and Switching Subsystem

NSS 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 the domain of the MSC - several BSC can belong to a MSC

Home Location Register (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 Location Register (VLR) local database for a subset of user data, including data about all user

currently in the domain of the VLR

Network and Switching Subsystem

ComponentsAuC : Authentication Center

EIR : Equipment Identity Register

OMC : Operation and Maintenance Center


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

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

subsystem

Network Databases

Summary

Interfaces

Overview



Geographical network organization

MSC region•The International GSM/DCS system area comprises all countries where PLMN is implemented•Within these countries, the PLMN are further subdivided into MSC areas

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 information•System uses LA’s to locate a MS using broadcast messages.

Overview



GSM numbering

Permanent subscriber numbering

MSRN & TMSI

IMEI, LAI & CI

Summary

Overview



Overview



a. MOC (Mobile Originated Call)b. MTC (Mobile Terminated Call)

Mobile Originated Call

1, 2: connection request

3, 4: security check

5-8: check resources (free circuit)

9-10: set up call

Mobile Originated Call

Mobile Terminated Call

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

Mobile Terminated Call

Detail Sequence of MTC

Future mobile telecommunication networks

04/2009. Overview 1. INTRODUCTION TO GSM 2. GSM ARCHITECTURE 3. GEOGRAPHICAL NETWORK ORGANIZATION 4....

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