All sections to appear here

GSM Network Architecture

Presenter : Manish Kumawat

Outline

• Introduction and history.

• GSM architecture.

• Implementation.

• Technology and standards.

• Summary

Introduction

• Global System for Mobile Communication (GSM)

– Anybody – 500 million users (may 2001)

– Anywhere – 168 countries (may 2001)

– Any media – voice, messaging, data, multimedia

Source: Hillebrand, 1

GSM Specifications

Carrier Separation - 200 kHz

No. of RF Carriers - 124

Access Method - TDMA/FDMA

Modulation Method - GMSK

Transmission Rate - 270.833 Kbps

Speech Coding - Full rate 13 Kbps

Half rate 6.5 Kbps

Duplex Distance - 45 MHz

GSM FDMA(Frequency Division Multiple Access)

25 MHz 25 MHz

Mobile to Base

0 1 2

890.2 890.4 890.6(MHz)

Base to Mobile

0 1 2

935.2 935.4 935.6

200 kHz45MHz

Channel layout and frequency bands of operation

890 935 960915

200 kHz

GSM TDMA(Time Division Multiple Access)

87

65

43

21

87

65

43

21

45 MHz

Frequency

F2’F1’

(Cell transmit)

F2F1

(Cell Rx)

Amplitude

Typical TDMA/ FDMA frame structure

FDMA/TDMA Scheme

BP1

BP2

BP3

BP4

BP5

BP6

BP7

BP8

BP1

BP2

TIME

890.0890.2

890.4890.6

890.8891.0

891.2 915.8

FREQ

MHz

BURSTF

R

A

M

E

GSM Architecture

OMC

Home Location Register

AuC

Equipment ID

Network

Management

Center

B

T

S

B

T

S

B

T

S

ME

ME

ME

Subscriber

Identity

Module

Subscriber

Identity

Module

Subscriber

Identity

Module

Base station

controller

PSTN

Mobile

switching

center

Data

communication

network

BTS = Base Transceiver Station

AuC = Authentication Center

OMC = Operation and Maintenance Center

PSTN = Public Switched Telephone Network

ME = Mobile Equipment

Source: Stallings, 313

Source: Mehrotra, 27

Visitor Location

Register

GSM Architecture

F1 F2 F1' F2'

Frequency

1

2

3

4

5

6

7

8

Year Introduced 1990

Access method TDMA

Channel Bandwidth 200 kHz

Number of duplex

channels

125

Users per channel 8

Speech coding bit

rate

13 kbps

Data coding bit rate 12 kbps

Frame size 4.6 ms

45 MHz

BS Transmission

Band : 935 – 960

MHZ

MS Transmission

Band : 890 – 915

MHZ

SIM (Subscriber Identity Module)

Billions of Calls

Millions of Subscribers

Thousand of Different Types of Telephones

Hundreds of Countries

Dozens of Manufacturers….

And only one Card: The SIM

Source: Hillebrand, 369

http://ucables.com/products/simcards/

•Administrative data

•Security data

•Subscriber data

•Roaming data

•PLMN (Public Land Mobile Network

Implementation

SIM = Subscriber Identity Module

Central processor, clock and tone, internal bus system, keyboard (HMI)

Voice encoding Ciphering Modulation

Voice decoding

>Channel Decoding

>De-Interleaving

>Re-formatting

Deciphering

Amplifier

>Channel encoding

>Interleaving

>Burst generation

Receiver

Transmitter

Demodulation

Source: Heine, 14

Implementation

Abis-

Interface

O&M Module Operation and maintenance functionality/clock distribution

Digital signal

processing (NF

functionality)

HF Transmitter

(HF-TX)

Input filter

Output filter

HF Receiver

(HF-RX) Slo

w f

requ

en

cy

ho

pp

ing

Tra

nsm

issio

n

syste

m

TRX

Block Diagram of a BTS with one TRX

Source: Heine, 20

GSM Variants

Variant Uplink

(MHz)

Downlink

(MHz)

Total

Bandwidth

Duplex-

frequency

Channels

GSM-400 451-458 and

479-486

461-468 and

489-496

Twice 14 MHz 10 MHz Twice 72

GSM-900

(primary

band)

890-915 935-960 Twice 25 MHz 45 MHz Twice 124

Extended

GSM-900

880-915 925-960 Twice 35 MHz 45 MHz Twice 174

GSM-R 876-880 921-925 Twice 4 MHz 45 MHz Twice 19

DCS-1800 1,710-1,785 1,805-1,880 Twice 75 MHz 95 MHz Twice 373

PCS-1900 1,850-1,910 1,930-1,990 Twice 60 MHz 80 MHz Twice 300

Source: Bekkers, 299

References

Bekkers, Rudi. Mobile Communications Standards: GSM, UMTS, TETRA, and ERMES. Norwood, MA: Artech House, Inc., 2001.

Halonen, Romero, and Melero. GSM, GPRS, and EDGE Performance: Evolution Towards 3G/UMTS. England: John Wiley & Sons Ltd., 2003.

Hillebrand, Friedhelm. GSM and UMTS: The Creation of Global Mobile Communications. England: John Wiley & Sons Ltd., 2002.

Heine, Gunnar. GSM Networks: Protocols, Terminology, and Implementation. Norwood, MA: Artech House, Inc., 1999.

Mehrotra, Asha. GSM System Engineering. Norwood, MA: Artech House, Inc., 1997.

Harte, Levine, and Livingston. GSM Superphones. United States: APDG Publishing, Inc. A Division of McGraw-Hill, 1999.