Introduction To GSM Network Design

- Shaun Roberts

What is GSM?

• Global System for Mobile Communications • Standard for Second Generation Cellular Networks • Introduced in 1990 by European Telecommunications

Stanards Institue • By 2009 GSM technologies accounted for 3.38 billion

subscribers globally and 83.5 percent of the mobile market share.

Overview

• 850Mhz, 950Mhz, 1800Mhz, and 1900Mhz • Conceived for full duplex voice telephony, the design of

the network was circuit switched. • General Packet Radio Services added packet switching for

data services such as text and internet usage.

Mobile Stations

• Most familiar component • SIM holds International Mobile Subscriber

ID, Auth. Key, User Contacts etc. • Mobile Device + SIM = Mobile Station

Keyboard

Control

Display

Transmit AudioSignal

Processing

Receive AudioSignal

Processing

ChannelDecoding

DeinterleavingMessage

Regenerator

ChannelEncoding

InterleavingMessageGenerator

Ciphering

Ciphering

RFProcessing

RFProcessing

SIMDuplexer

Antenna

ANTENNAASSEMBLY

TRANSMITTER

RECEIVER

TRANSCEIVER UNITCONTROLSECTION

Multiple Access

• Frequency Division Multiple Access • Radio Bands split into Frequency

Channels

Multiple Access (cont.)

• Time Division Multiple Access • Splits each Frequency Channel Into 8

Timeslots

BSS – Base Station Subsystem

• Large number of Base Transceiver Stations connected to Base Station Controllers

• Connect Mobile Station to Network

BTS – Base Transeiver Station • Controls

Transceivers and Antennas

• Each BTS can have 16 TX/RX

• 8 Users per TX/RX

BSC – Base Station Controller

• Manages multiple BTS’s

• Essentially small exchange

NSS – Network and Switching Subsystem

• Mobile Switching Centers and Subscriber Databases

• Manages communication and services

MSC – Mobile services Switching Center • Switches Calls • Provides connection to other

networks • Processing of service

features

HLR/VLR/AuC

• Home Location Register • Visitor Location Register • Authentication Center

GPRS Core Network

• Added packet switching to GSM

• Packet Control Unit, Serving GPRS Support Node, Gateway GPRS Support Node

SGSN – Serving GRPS Support Node GGSN – Gateway GRPS Support Node

Sources

• Eberspacher, J; Bettstetter, Christian; Vogel, Hans-Joerg; Hartmann, Christian. (2009). GSM - Architecture, Protocols and Services. Wiley. Heine, Gunnar. (2003). GPRS : Gateway to Third Generation Mobile Networks (Second Edition). Artech House.

• ETSI TS 100 910 V8.20.0 Technical Specification