• GSM ArchitectureGSM Fundamentals

•At the end of this learning element, the student should be able to:

– Name the three subsystems of GSM.– List eight different network elements (generic architecture) and

name at least one task per element.– Describe the benefits of a Release 4 core network.

Objectives

•Where is the subscriber

•Who is the subscriber

•What does the subscriber want

•Information about the subscriber

Mobile Subscriber

The Mobile Station MS

GSM Mobile Station

A

NMSNMS

NSSNSSBSSBSSO&M

Air

MS

Network Switching Subsystem

• Switching• Mobility Management• Connection Management• Charging

Base Station Subsystem• Radio Resource Management• Radio Link Management

Network Management System

• Fault Management• Configuration Management• Performance Management

GSM PLMN Organization

GMSC

VLR

MSC

HLR

HLR

AC

EIR

MSC Mobile services Switching CentreGMSC Gateway MSCVLR Visitor Location RegisterHLR Home Location RegisterEIR Equipment Identity RegisterAC Authentication Centre

Network Switching Subsystem

MSC GMSC• Call control• Mobility management• Initiation of paging• Collection of changing information• Often associated with VLR

• Call control• Interrogation of HLR• Collection of changing information• Often used for interworking with external networks

Mobile services Switching Centre (MSC)

VLR• Identification numbers of subscribers• Security information• Services that the subscriber can use

HLR• Subscriber Profile• Routing Information

AC• Data for authentication (SIM)

and ciphering

EIR• Lists for Mobile Equipment (ME) checks

Registers in the NSS

SRRiDatabase

HLR HLR

MSCSGSN

MSISDN1 - rerouting info

MSISDN2 - rerouting info

.

.

1

………

Othernetworks

Mobile Number Portability Solution - SRR

PSTN

MSC Server

Site 1R

NC

2

RN

C2

MG

W

Site 2R

NC

3

RN

C3

MG

W

Site 3

RN

C4

RN

C4

MG

W

Site 4

Inter-Site

Transport

Network

Only control plane is routed to the core network site

User plane is optimized between access network sites

User plane is optimized within the same access network site

POI

User plane is optimized for PSTN

calls

MSC Server + MGW Concept (Separation of control and user plane traffic)

HLR

MSC-Server

GMSC-Server

CS-MGW

CS-MGW

UTRAN

GERAN

PSTN, ISDN,PLMN, etc.

CSE

CAP CAP

Iu

IuA

A

D C

Nc

Nb

Mc(H.248)

Mc(H.248)

Rel-04 Architecture

Base Station Subsystem

• Elements: – Base Station Controller (BSC), Base Transceiver Station (BTS), and

Transcoder and Rate Adaptation Unit (TRAU, TC)• Functions:

– Radio path control, BTS and TC control, synchronisation with MSC– Air and A interface signaling, connection establishment MS-NSS– Mobility management, speech transcoding– Collection of statistical data

BTS

TCBSC

BSC

TCBTS

BTS

Base Station Controller (BSC)

– Connection establishment between MS and NSS– Mobility management– Statistical raw data collection– Air- and A-interface signaling support – BTS and TRAU Control

BSC

Base Transceiver Station (BTS)

– Air interface signaling – Ciphering– Speech processing (channel coding, interleaving, and burst formatting)– Generation of alarms and statistics– Baseband/Radio frequency transformation

Omnidirectional BTS

f1,f2, f3

3 sectorized BTS

2 sectorized BTS

f2

f1, f2

f5, f6

f1

f3, f4

BTSBTS

BTS

BTS

BTS BTS

f = carrier frequency band

Omnidirectional and Sectorized Cells

A InterfaceA ter’ Interface

A ter Interface

MSC

SM2M

TC

TC

TC

TC

Transcoder andSubmultiplexer (TCSM)BSC

Position of the Transcoder

Data CommunicationsNetwork

BTS

BTS

BTS

BTS

DN2

BSC

MSCVLR

HLRACEIR

SMSC

NMS/2000

Network Management Subsystem

Functions of NMS (1)

•Fault management– Collection of alarm reports from network elements.– One point for managing all fault situations.

Functions of NMS (2)

•Configuration management– Management of radio network configuration.– Maintain up to date information on the network element

status.

Functions of NMS (3)

•Performance management– Collection of measurement data from network elements.– Produce performance result from raw data.

BSC

TCBTS

BTS

VLR

(G)MSC

EIRHLR AC

Um

AAterAbis

B C

D

VLRG

F

(G)MSC

E

BSS NSS

BSC

TCBTS

BTS (G)MSC

Um

AAterAbis

B C

DVLR

EIRHLR AC

VLRG

F

(G)MSC

E

BSS NSS

Interfaces

ACEIR

BTS

OMC

MSCVLR

HLR

BSC

BTS

BTS

BTS

BTS

BSC

BSS - Base StationSubsystem

NSS - Network Subsystem

NMS - Network Management SystemMS

AbisAir A

IWF

SCPSPDN

PSTNISDN

Transcoder

Generic GSM Architecture