L1 - GSM Alcatel Introduction

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Alcatel University - 8AS 90125 0143 VT ZZA Ed.01 Page 1

Introduction to theAlcatel 900/1800/1900 GSM netw ork


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Introduction to the Alcatel 900/1800/1900 GSM Network

1 Introduction

2 General Specification

3 Services Provided

4 Radio Interface

5 Interchanges over the Network

6 Alcatel 900 / 1800 / 1900 Solution

Appendix


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Introduction to the Alcatel 900/1800/1900 GSM Network

1 Introduction


4/104 Alcatel University - 8AS 90125 0143 VT ZZA Ed.01 Page 4

IntroductionContents

1.1 GSM 900 / 1800 / 1900

1.2 History of Cellular Networks

1.3 Lim its of GSM System s

1.4 Overview of Current Standards

1.5 GSM Key-Dates

1.6 International Agreem ents: "M em orandum Of Understanding"

1.7 Contribution of GSM Standard

1.8 Contents of GSM "Recom m endations"



INTRODUCTION1.1 GSM 900 / 1800 / 1900

GSM : GlobalSystem forMobile com m unication

Pan-European standard for com m unication with m obiles, already adopted by

m ore than 60 countries and now the worldwide reference for m obile radionetworks. Since 1995 (phase 2), this standard harm onizes the 900 M Hz GSM

system and the 1800 or 1900 M Hz Digital Cellular System s (DCS).

GSM 900: 2 x 25 M Hz frequency bands around 900 M Hz.

GSM 1800:

2 x 75 M Hz frequency bands around 1800 M Hz.

GSM 1900: (North and South Am erican variant of the GSM 1800):

2 x 75 M Hz frequency bands around 1900 M Hz.



INTRODUCTION1.2 History of Cellular Networks

M obile network "Prehistory":

1946:St Louis (M issouri)

1970 - 80: NATEL (Switzerland)

1stGeneration: ANALOGUE cellular netw orks

1979: Chicago: AM PS

1981: Sweden: NM T

1985: UK: TACS

2nd Generation: DIGITAL networks

1992: Europe: G SM

1995: US: IS95 (CDM A)

3rd Generation: Universal(?) Standards

2002: IM T 2000



INTRODUCTION1.3 Lim its of GSM system s

public

residential

office PABX

PSTN

PABX

PSTN

PSTN

Sm all Cells M edium Cells Large Cells

GSM


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Standard CT2 GSM DCS DECT IS95

System type cordless cellular cellular cordless satellite

Frequencyband (M Hz) 864 - 868 890 - 915 ()1710 -1785 () 1880 -1900 1610 -1626.5 ()

935 - 960 () 1805 -1880 () 2483.5 -2500 ()

Com m ercial Pointel Itinris Bouygues Digital Globalstar

nam es Bi-bop SFR Telecom dom esticcordless

telephones

Com pany

m obiles

INTRODUCTION1.4 Overview of current standards


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INTRODUCTION1.5 GSM key dates

1979 W orld Adm inistrative Radiocom m unications Conference

(W ARC) : 900 M Hz band reserved

1982 Stockholm - Creation of the "Groupe Spcial M obile" within

CEPT (Post & Telecom European Conference)

1986 Creation of a GSM " Standing Com m ittee

CNET Paris : Com parative trials of 8 prototypes

1987 "Broad Avenue" : Choice of m ain techniques:

M edium Band - Digital Transm ission < 16 kbit/s - 8 x Tim e-division m ultiplexing, subsequent developm ent to 16 x - Slow frequency

hopping

1988-89 GSM taken over by ETSI

First publication of the (Draft) "recom m endations"

1990 Beginning of studies for adaptation to 1800 M Hz (at UK's request)

1990-91 "Phase 1" recom m endations fixed (GSM , then DCS)

First GSM prototypes in service (Tlcom '91 Geneva)

1992 First com m ercial GSM networks placed in service

1995 "Phase 2" recom m endations issued (upward com patibility)


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GSM - M oU: M em orandum of understanding

signed on 87/09/07 between european

operators

1991: acceptation of non-european

signatories (UAE, Hong Kong,

New Zealand, Australia)

Scope:

. System deploym ent schedule

. Routing and num bering plancom patibility

. Joint introduction of new services

. Harm onization of tariff setting principles

. Definition of billing procedures

INTRODUCTION1.6 International agreem ents

European G SM -M oU signatories (operators) in 199

3

23 4

3

42

33

2

4

3 34

5

2

3

3

4

2

3


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INTRODUCTION1.7 Contribution of GSM standard

Pan-European standard + M oU

GLOBAL system (standardized infrastructure)

New concept: SIM card ("SIM -roam ing")

Digital transm ission, speech encoding

Introduction of state of the art techniques

Integrated security procedures

Considerable potential m arket


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INTRODUCTION1.8 Contents of GSM recom m endations

GSM recom m endations : series

01 G eneral aspects

02 Definition of services 03 Network Aspects

04 M S - BS interface and protocols

05 Radio Interface: Physical level

06 Speech encoding/ decoding

07 Term inal Adapters

08 BS - M SC interfaces

09 Interworking

11 Equipm ent

12 Operation and M aintenance


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GPRS General Packet Radio Service (1)

01.60: Requirem ents specification of G PRS

01.61: G PRS ciphering algorithm requirem ents 02.60: Service description; stage 1

03.60: Service description; stage 2

03.64: O verall description of the G PRS radio interface; Stage 2

04.60: M obile Station (M S) - Base Station System (BSS) interface; Radio

Link Control / M edium Access Control (RLC/M AC) protocol

04.64: M obile Station (M S) - Serving G PRS Support Node (SGSN); Logical

Link Control (LLC) layer specification 04.65: M obile Station (M S) - Serving G PRS Support Node (SGSN);

Subnetwork Dependent Convergence Protocol (SNDCP)

07.60: M obile Station (M S) supporting G PRS


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GPRS General Packet Radio Service (2)

08.14: Base Station System (BSS) - Serving GPRS Support Node (SGSN)

interface; Gb interface layer 1


interface; Network Service


interface; BSS GPRS Protocol (BSSGP) 09.16: Serving G PRS Support Node (SG SN) - Visitors Location Register

(VLR); Gs interface network service specification

09.18: Serving G PRS Support Node (SG SN) - Visitors Location Register

(VLR); Gs interface layer 3 specification

09.60: GPRS Tunnelling Protocol (GTP) across the Gn and G p Interface

09.61: Interworking between the Public Land M obile Network (PLM N)

supporting G PRS and Packet Data Networks (PDN)

12.15: GPRS charging


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INTRODUCTION TO THE Alcatel 900/1800/1900 GSMNETW O RK

2 General Specifications


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GENERAL SPECIFICATIONSContents

2.1 General Concepts in Cellular Networks

2.1.1 PLM N and M obile Stations

2.1.2 Cellular Coverage

2.1.3 Data Transm ission

2.2 GSM Architecture

2.2.1 Types of M obile Stations

2.2.2 PLM N Elem ents

2.2.3 Base Station System

2.2.4 Network and Switching System

2.2.5 GPRS

2.2.6 Operation and M aintenance

2.3 GSM Interfaces and Protocols

2.4 Position of Transcoding Unit (TRAU)


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PLM N = Public Land M obile Netw ork

PSTN = Public Sw itched Telephone Netw ork

ISDN = Integrated Services Digital Netw ork

PDN = Packet Data Netw ork

GENERAL SPECIFICATIONS2.1.1 General Concepts: PLM N and M obile Stations

ISDN

PSTN

PDN

PLMN


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GENERAL SPECIFICATIONS2.1.2 General Concepts: Cellular Coverage

om nidirectional antenna

sectored antenna

directional antenna

Base StationBase Station Controller

KEY

(25)

(25)

(25)

(25)

(25)

150

traffic Erlangs (BSC)150traffic in Erlangs (BTS)(25)

150

150

100 50

300

300

50

50

50

200


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Exam ple of 12-Cell Three-sector Pattern

Frequency Reuse Pattern

12

3 10

14 7 8

692

5

11

12

3 10

14 7 8

692

5

11

12

3 10

14 7 8

692

5

11

12

3 10

14 7 8

692

5

11

12

14 7 8

692

5

11

D


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0 or 4

1 or 5

2 or 6

3 or 7

NCC

International Colour Codes


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Radio Resources are lim ited

To increase Spectrum efficiency,

specific techniques are introduced: Power Control

Handover

Frequency Hopping

Discontinuous

transm ission (DTX)

downlink

uplink VIP

GSM antenna


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GENERAL SPECIFICATIONS2.2 GSM architecture

MSBSSNSS

OSS

OPERATORS

NETWORKS USERSEXTERNAL

GSM


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GENERAL SPECIFICATIONS2.2.2 GSM architecture: PLM N Elem ents

BSC

BTS

BTS

BTS

BTS

BTSBTS

BTS

BSC

M SC

VLR HLR AuC EIR

PSTN,ISDN...

OM COM C

NM C

X.25 links

GSM interfaces

Voicem ail Server

SM -SC

M S(M obile Station)

BSS(Base Station System )

NSS

(Network & Switching System )

OSS(Operation & m aint. Sub System )

GCR

Base station system BSS

BTS Basic Transceiver Station

BSC Base Station Controller

Network and switching systemMSC Mobile Switching Centre

HLR Home Location Register

VLR Visitors Location Register

AuC Authentication Centre

Optional

EIR Equipment Identification Register

Voicemail Server

SM-SC Short Message Service Centre

GCR Group Call Register

Operation and maintenance subsystem OSS

OMC Operation and Maintenance Centre

[NMC Network Management Centre]


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GENERAL SPECIFICATIONS2.2.3 GSM architecture: Base Station System

BSC

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BSC

NSS CBC

MAIN FUNCTIONS:

BTS

PHYSICAL CHANNEL MANAGEMENT(on Radio channel)

BSC

MANAGEMENT OF INTERFACES WITHNSS & OSS

MANAGEMENT OF RADIO "LOGICAL"

CHANNELS

BTS MONITORING

CBC : Cell Broadcast Centre (optional)

Buffer STORAGE and Generation of

CELL BROADCAST SHORT MESSAGES


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GENERAL SPECIFICATIONS2.2.4 GSM architecture: Network and Switching System

M SC

VLR HLR AuC

PSTN,ISDN...

BSS

MSC

CALL HANDLING (subscriber exchange)

RADIO RESOURCE MANAGEMENT

- VLR/HLR database updating

- Subscriber radio paging- Handover management

GATEWAY FUNCTION

for terminating calls

HLR

Reference DATABASE (for a region)

STORES: Identities - Directory numbers -

Services subscribed + Approx. location (VLR)

VLRLOCAL DATABASE

(associated with one or more MSCs)COPIES HLR data for VISITING subscribers

ACCURATE LOCATION of visiting subscribers

Call redirection DATA

AuC

SECURITY DATABASE

(authentication and encryption)

GENERATION of KEYS


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GENERAL SPECIFICATIONS2.2.4 GSM architecture: Network and Switching System

M SC

SM -SC

EIR

BSS

Voice M ail Server

GCR

MAIN FUNCTIONS:

EIRMobile EQUIPMENT DATABASE

CONCEPT of "white", "grey" and "black" mobile

Voice Mail ServerVOICE MESSAGING SERVER

(not specified in GSM standard)

SM-SCSHORT MESSAGE STORAGE

during subscriber unavailability

GCR : Group Call Register(optional)

VOICE CALL GROUP SERVER

(new services in phase 2+, PMR type)


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GENERAL SPECIFICATIONS2.2.5 GSM architecture: GPRS

Data

MSC/VLR

GSM+GPRS

BSS with

PCU

ISDN

GPRS

Backbone

SGSN

Internet

GGSN

GPRSGPRS

MobileMobile

Voice

BSS

HLR


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NSS

(O M C-M or S)(O M C-R)

NM C

BSS

OM C: ConfigurationFault

Perform ance

Security

Cost

NM C: Telecom M anagem ent Network

(optional)

GENERAL SPECIFICATIONS2.2.6 GSM architecture: Operation and M aintenance

GPRS

(O M C-G )

OM C

G S C C O S


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GENERAL SPECIFICATIONS2.3 GSM interfaces and protocols

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BSC

M SC

VLR HLR AuC EIR

PSTN,ISDN...

VLR

M SCE

B C

D

F

G

H

GCR

I

BSC

Abis

Um (Radio)

A

B

C

D

E

FG

H

I

PSTN

ISDN

BTS - BSC

BSC-M SC (SS7 basic)

M SC-VLR

(SM -G )M SC-HLR

HLR-VLR

(SM -G )M SC-M SC (SS7 basic)

M SC-EIRVLR-VLR

HLR-AuC

M SC-G CR

M SC-PSTN (SS7 basic)

M SC-ISDN

LAPDm(GSM specific)

LAPD(ISDN type)

+ BSSAP

+ M AP

+ TUP or ISUP

M

S

M

S M

S

M

S

M

SM

S M S - BTS

GSM Circuit-switching:

GENERAL SPECIFICATIONS


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Gc G G SN-HLR (IP)/SS7

LAPD(ISDN type)

LAPDm(GSM specific)

GENERAL SPECIFICATIONS2.3 GSM interfaces and protocols

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BSCBSC

Gs

Gb

Um (Radio)

Abis

G i G G SN-Data Netw orkIP

M

S

M

S M

S

M

S

M

SM

S

BTS - BSC

BSC-SG SN

Gr SS7SG SN-HLR

Gf SS7SG SN-EIR

SG SN-M SC/VLR

G n

IP

IP

SGSN-GG SN

SG SN-SG SN

M S - BTS

SGSN

HLR

Data Netw ork

M SCGs

EIR

G fGr

SGSN Gn

GGSN

G n

Gi

Gc

SS7

GSM Packet-switching (GPRS):

GENERAL SPECIFICATIONS


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GENERAL SPECIFICATIONS2.4 Position of Transcoding Unit (TRAU)

BTS BSC M SCVLRTRAU

BTS BSC M SCVLRTRAU

BTS BSC M SCVLRTRAU

Abis interface A interface

16 kbit/s transm ission64 kbit/s transm ission

KEY :

INTRODUCTION TO THE Alcatel900/1800/1900 GSM


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3 Services Provided

SERVICES PROVIDED


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SERVICES PROVIDEDContents

3.1 Teleservices

3.1.1 Teleservices and Bearer Services

3.1.2 Categories of Teleservices

3.1.3 Principle

3.1.4 Data transm ission in circuit m ode

3.1.5 Data transm ission in packet m ode

3.2 Supplem entary services 3.2.1 Num ber Identification Services

3.2.2 Call Forwarding Services

3.2.3 Call Com pletion Services

3.2.4 M ulti-Party Services

3.2.5 Billing Services

3.2.6 Call Barring Services

3.2.7 Phase 2+ Services

3.2.8 Sundry Services

SERVICES PROVIDED


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SERVICES PROVIDED3.1.1 Teleservices and Bearer Services

Teleservice:Transm ission capability including term inals and applications

Bearer Service:Transm ission capability between defined userInterfaces

Transparent and Non-Transparent Services and Bearer Services

Transparent :Fixed rate, no flow control: fast but high error ratio

Non-Transparent :RLP added: low error ratio, slower transm ission

G SM

PLM NIW F IW F

Transit

netw ork,

if any

Term inating

netw ork

TE = Term inal Equipm ent IW F = InterW orking Function

Teleservices

Bearer services

TE

TE

SERVICES PROVIDED


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SERVICES PROVIDED3.1.2: Categories of Teleservices

Voice Services:

Telephony

Em ergency Calls

Voice Call G roups (Groups of m obiles sharing lim ited radio resources)

(Voice M essaging: not identified by the G SM as a specific service)

Short M essage Services (SM S):

PO INT-TO-PO INT, Network to M obile (SM S - M T/PP)

PO INT-TO-PO INT, M obile to Network (SM S - M O/PP)

BROADCAST, Network to M obile (SM S - CB)

Other Non-Voice Services

SERVICES PROVIDED


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SERVICES PROVIDED3.1.3 Teleservices: principles

By com parison with PSTN access, the entire GSM infrastructure can be treated as a DTE-DCE line

between the term inal and the M ODEM which is inserted by the network.

PSTN user PSTN userAudio m odem Audio m odem

3.1 kHz audio line

PSTN

Conventional connection PSTN user < -- > PSTN user

GSM user

Audio m odem

3.1 kHz audio line

PSTN

Audio m odemPSTN user

GSM infrastructure

Connection G SM user < -- > PSTN user

(DTE) (DCE)

Standard interface

(DCE) (DTE)

Standard interface

Standardized transm ission

Standard interfaceIW F

GSM transm ission Standardized transm ission(DCE) (DCE)(DTE)(DTE)

Standard interface

SERVICES PROVIDED


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S C S O3.1.3 Teleservices: principles

General Principles:

DIGITAL transm ission on the radio channel

AUDIO M O DEM inserted at the interworking point (IW F) between the two

networks (generally in the M SC)

Data Transm ission Services:

Usable M ODEM TYPES defined by the GSM standard:

V21: 300 bit/s asynchronous

V22: 1200 bit/s, asynchronous or synchronous

V22 bis: 2400 bit/s synchronous

V23: 1200/75 bit/s asynchronous

V26 ter: 2400 bit/s synchronous

V32: 4800 or 9600 bit/s synchronous

SERVICES PROVIDED


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3.1.4 Teleservices: Data transm ission in circuit m ode

DIG ITAL radio transm ission ==> FAX adapter function (including audio m odem + T30 functions)

Standard TAF: synchronous inform ation bearer (as for data transm ission services)

Audio M O DEM : includes V21 - V27 ter and V29 protocols essential for dialogue betw een FAX m achines

3.1 kHz audio line

PSTN

Conventional connection PSTN user < -- > PSTN user

Audio m odem3.1 kHz audio line

PSTNG SM infrastructure

Connection G SM user < -- > PSTN user

Standard FAX m achineAudio m odem

Standard FAX m achineAudio m odem

Standard FAX m achine

Audio m odemStandard FAX m achine

Audio m odemAudio m odem

TAF

FAX adapter

G SM user

SERVICES PROVIDED


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3.1.5 Teleservices: Data transm ission in packet m ode

Services provided:

All Personal m obilityapplication

Internet Access

Car Traffic m anagem ent

G SM Netw ork Packet Data Netw ork

Virtual Circuit

Internet

Datagram

User 1

User 2

User 3

GGSN

GGSN

SGSN

W ith Quality Of Service profiles:

Service Precedence (Priority) Reliability

(Transfer) Delay

Use Data Throughput

SERVICES PROVIDED


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3.2.1 Supplem entary Services

Num ber identification services

CLIP Calling Line Identification Presentation (term inating call)

Lets the called party receive the caller's identity (applicable to all

services except SM S)

CLIR Calling Line Identification Restriction (originating call)

Lets the caller withhold his num ber from the called party

(either perm anently or on a per-call basis) CoLP Connected Line Identification Presentation (originating call)

Indicates the party's num ber when the call has been set up

CoLR Connected Line Identification Restriction (term inating call)

Lets the called party withhold his num ber from the caller

(either perm anently or on a per-call basis)

M CI M alicious Call Identification

Lets the network store call param eters

(called and calling party num bers - date - tim e)

SERVICES PROVIDED


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Call forwarding services

CFU Call Forwarding Unconditional

These four services are used to forward calls to the local PLM N or to

another PLM N (Id = International num ber)

CFB Call Forwarding on m obile subscriber Busy

Up to five consecutive forwarding operations(system param eter)

CFNRy Call Forwarding on No ReplyCalling/called party notification possible

CFNRc Call Forwarding on m obile subscriber Not Reachable

O verall deactivation possible

CD Call Deflection

Lets the m obile subscriber screen out calls (with CLIP) and forward

calls as required on a per-call basis


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SERVICES PROVIDED


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M ulti-Party services

M PTY M ulti Party service

Conventional options: Hold - Retrieval of first call or transition to

conference

CUG Closed User Group

O ptional allowing or barring of incom ing or outgoing calls

(OA/IA - O CB/ICB) - Preferential CUG allowed ECT Explicit Call Transfer

W ith m obile A connected to two parties, B and C, these two parties

can be connected and A can withdraw (telephone call only)

SERVICES PROVIDED3 2 5 l i


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Billing services

AoCI Advice of Charge - Inform ation

Advice of call charge at end of call or in real tim e. Applicable to all

services, except short m essages and packet data

AoCC Advice of Charge - Charging

Calls barred when the m obile is located in a PLM N not providing this

service

REVC Reverse Charging Service elim inated in phase 2

SERVICES PROVIDED3 2 6 S l t S i


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Call Barring services

BAOC Barring of All Outgoing Calls

BOIC Barring of Outgoing International Calls

BOIC-ex HC Barring of Outgoing International Calls, except those

directed to the Hom e PLM N Country

BAIC Barring of All Incom ing Calls

BIC-Roam Barring of All Incom ing Calls w hen Roam ing

outside the Hom e PLM N country*

for all:

Barring except em ergency calls

Subscription possible for any com bination

Activation protected by password

SERVICES PROVIDED3 2 7 S l t S i


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Phase 2+ services

UUS User to User Signalling

Allows sending or receiving of user-to-user short m essages during a

com pleted call or during call set-up

eM LPP Enhanced M ulti_Level Precedence & Preem ption

Allows one of seven precedence levels to be assigned to som e m obiles

so that they can set up calls rapidly (no authentication), in som e cases

cutting off calls of lower precedence

SNPN Support of Private Num bering Plan

Access to a virtual private network (VPN) with private num ber

translation handled by an external PN m anager

SERVICES PROVIDED3 2 8 Supplem entary Services


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Sundry services

M SP M ultiple Subscriber Profile

Allows up to 4 subscriber profiles for the sam e SIM card

NITZ Network Identity and Tim e Zone

Transfers the network identity and local tim e to the term inating m obile

PDS Packet Data on Signalling Channel

PTP transfer (circuit-oriented) of very short data packets between am obile and a host

ODB Operator Determ ined Barrings

Allows the service provider to apply24 different types of call barring

CAM EL Custom ized Applications for M obile network Enhanced

Logic

Allows for supplem entary services specific to a given operator (for

exam ple, INSS) outside the origin PLM N

SO R Support of Optim al Routing

O ptim ized call forwarding to avoid "trom boning"



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NETW O RK

4 Radio Interface

RADIO INTERFACEContents (1)


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Contents (1)

4.1 Introduction 4.1.1 Im portance of the Radio Interface

4.1.2 Traffic and Signalling

4.1.3 M obile Station Status (Circuit and Packet Switched M ode)

4.1.4 Radio Resources

4.2 Physical Channels : M ultiple Access Diagram 4.2.1 Frequencies

4.2.2 TDM A Fram e 4.2.3 Norm al Burst

4.3 Logical Channels 4.3.1 Principle

4.3.2 Tim e-Division M ultiplexing on a Physical Channel 4.3.3 Channel M apping

4.3.4 Tim ing Advance

4.3.5 Paging

4.3.6 Access to the Network 4.3.7 Logical Channel Sum m ary

RADIO INTERFACEContents (2)


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Contents (2)

4.4 Speech Processing

4.4.1 Radio Channel Generation

4.4.2 Discontinuous Transm ission 4.4.3 GM SK M odulation

4.5 Radio Techniques

4.5.1 Frequency Hopping

4.5.2 Power Control

4.5.3 Space Diversity

RADIO INTERFACE4.1.1 Im portance ofthe radio interface


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4.1.1 Im portance of the radio interface

RADIO INTERFACE : essential part of GSM specifications because of:

Inter-PLM N CO M PATIBILITY ==> Com plete Specification

(to the nearest bit)

Very elaborate SPECTRUM EFFICIENCYoptim ization techniques:

Reduction of INTERFERENCE to M anage a large num ber of M obiles per km

RADIO INTERFACE4.1.2 Traffic and Signalling


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4.1.2 Traffic and Signalling

TRAFFIC :

INFORM ATION interchanged from USER-TO-USER, after setting up the

call, requiring dedicated radio resource allocation.

In GSM , TRAFFIC can be an interchange of SPEECH or DATA

SIGNALLING :INFORM ATION interchanges (in som e cases, without the user's

knowledge) between the M OBILE EQUIPM ENT and NETW ORK

M ACHINES

Out of Call : required for m anaging m obiles, eg. : location update

During a Call : required for various reasons, eg. : handover, access to

a supplem entary service, call release

RADIO INTERFACE4.1.3 M S status


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Detac

hAttac

h

"Connected"

"Power Off"

"Idle"

Endo

f

tra

nsactio

nNe

tworkA

ccess

Circuit Switching M ode

M S not

reachable

M S

reachable

RADIO INTERFACE4.1.3 M S status


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"Idle"Attachm

entto

network

Deta

chment

O ut of Tim e

Packet Tx or Rx

Detachm

ento

rOut

ofTim

e

"Ready""Stand-by"

Packet Switching M ode

M S not

reachable

M S

reachable

RADIO INTERFACE4.1.4 Radio Resources


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Dedicated

Signalling

Channels

Com m on

Access

Channels

Com m on

Broadcast

Channels

Typical M obile - Network Transaction:

M obile

pre-synchronization

"Idle" Status "Connected" Status

Netw ork Access O ut of call

signalling phaseTRAFFIC phase

Access

procedure

(O ptional)

Channels

to be used

Dedicated

Traffic

Channels

M ain

Tasksand

Inter-

change

Types

Frequency

search

Tim ing

Synchro

System

Param eter

Analysis

(Paging)

Access

Request

Dedicated

Channel

Assignm ent

Authentication

Location Updating

Short M essages

(Traffic Channel

Assignm ent)

Traffic

Signalling

Frequency

Monitoring

RADIO INTERFACE4.2.1 Frequencies


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UPLINKBAND

(M S -> BTS)

DOW NLINK

BAND

(BTS -> M S)

frequencyaxis

900 bands

possible extension of G SM bands

(2 x 25 M Hz : 124 carriers)

(2 x 33 M Hz : 164 carriers)

1800 bands(2 x 75 M Hz : 374 carriers)

M Hz

M Hz

200 kHz

890

935

960

915

8801710

1785

1805

1880

915

960

925

RADIO INTERFACE4.2.2 TDM A Fram e


58/104


1 BTS (eg. 3 carriers)

Frequency shift

45 M Hz in 900,

95 M Hz in 1800,

22

17

7 cell "beacon" frequency

22

17

7

UPLINKBAND(M S -> BTS)

DO W NLINKBAND(BTS -> M S)

frequencyaxis

RADIO INTERFACE4.2.2 TDM A fram e


59/104


1 BTS (eg. 3 carriers)

TDM A fram e = 4.615 m s

1 "CHANNEL" (in 1 direction)

Sam e "CHANNEL" (if bidirectional)

tim e axis

Tim e slot (or burst w indow )

1 2 3 4 5 6 70 1 2 3 4 5 6 70 1 2 3 4 5 6 70

1 2 3 4 5 6 70 1 2 3 4 5 6 70 1 2 3 4 5 6 70

22

17

7

22

17

7

UPLINK

BAND

(M S -> BTS)

DO W NLINK

BAND(BTS -> M S)

frequency

axis

Tim e shift betweentransm it and receive : 3 TS


60/104

RADIO INTERFACE4.2.3 Norm al Burst


61/104


TRAINING SEQ UENCES :8 different bit patterns, chosen so that:

They are easily recognizable (very accurate auto-correlation function)

They are easily distinguishable from one another (little correlationbetween each pattern)

STEALING FLAGS:

26 bits

"Stealing Flags"

S = 0

S = 1

57 bits 57 bits+

+

TCH ( or SDCCH )

FACCH

Training sequence

57 bits 57 bits

RADIO INTERFACE4.3.1 Logical Channels


62/104


1 2 3 5 6 7TS

"Beacon" frequency

Tim ing synchronization

System inform ation

Subscriber paging

Response to access request

Out of call signalling -> M Si

Power Control -> M Si

Traffic sam ples -> M Sj

In call signalling -> M Sj

BTS M S

Traffic sam ple decoding

In call signalling receipt

Power Control

Out of call signalling receipt

M obile presynchronization

Subscriber paging

Response to access request

exam ple : "Beacon" frequency, downlink:

FCCH

SCH

BCCH

PCH

AGCH

SDCCH

SACCH

TCH

FACCH

FCCH

BCCH

PCH

AGCH

SDCCH

SACCH

TCH

FACCH

0 4

SCH

RADIO INTERFACE4.3.1 Logical Channel


63/104


Use of Logical Channelsduring transactions between Network and M obile Station

1 If the transaction is "M obile Term inated" (incom ing call), the m obile m ust be paged

2 The m obile accesses the PLM N network

3 The network allocates a dedicated channel to the m obile for signalling 4 Signalling interchange (SDCCH and SACCH).

If necessary, the network allocates a TRAFFIC channel to the m obile

5 Traffic interchange (speech or data) on TCH, with associated signalling in SACCH

(background tasks) and FACCH if required

SACCH FACCH

PCH RACH SDCCH + SACCHAG CH TCH / FACCH + SACCH

1 2 3 4 5

RADIO INTERFACE4.3.2 Tim e Division M ultiplexing


64/104


0 1 2 3 4 5 6 7TS

1 2 3 4 5 6 7 8 9 10 20 30 40 5051 1

1 2 3 4 5 6 7 8 9 10 20 23242526

M ultifram e = 51 fram es, giving 235 m s approx.

"TRAFFIC" type M ULTIFRAM E :

"SIGNALLING" type M ULTIFRAM E :

1 TDM A fram e = 120/26 # 4.615 m s

1 2 3 4 5 6 7 8 9 10 20 23242526

M ultifram e = 26 fram es, giving 120 m s

GSM (Circuit Switching)



65/104


1 2 3 4 5 6 7 8 9 10 20 30 40 5051 1

M ultifram e = 52 fram es, giving 240 m s.

52 Fram e - M ultifram e on pdch:52

0 1 2 3 4 5 6 7TS

1 TDM A fram e = 120/26 # 4.615 m s

GPRS (Packet Switching) (1)

Block 0 Block 1 Block 2 Block 3 Block 4 Block 5 Block 6 Block 7 Block 8 Block 9 Block 10 Block 11



66/104


1 2 3 4 5 6 7 8 9 10 20 30 40 5051 1

M ultifram e = 52 fram es, giving 240 m s.

52

GPRS (Packet Switching) (2)

Block 0 Block 1 Block 2 Block 3 Block 4 Block 5 Block 6 Block 7 Block 8 Block 9 Block 10 Block 11

TFI: Tem porary Flow Identifier:

created w hen data has to be transm itted and until all data have been transm itted

BSN: Block Sequence Num ber

Data Flow to User BData Flow to User A Data Flow to User C

TFI 43 TFI 2 TFI 39

TFI =43

Data

BSN =21

TFI =43

Data

TFI =43

Data

BSN =22BSN =23

TFI =43

Data

BSN =24

TFI =43

Data

TFI = 2

Data

BSN =25BSN =12

TFI = 2

Data

BSN =13

TFI = 2

Data

TFI = 2

Data

BSN =14BSN =15

TFI = 39

Data

BSN =75

TFI = 39

Data

TFI = 39

Data

BSN =76BSN =77

RADIO INTERFACE4.3.3 Channel M apping


67/104


STRUCTURE of the M ULTIFRAM E in "TIM E SLOT" 0 (DOW NLINK channel)

F S B B B B c c c c

31

-

51 1

M ultifram e of 51 fram es (giving 235 m s approx.)

F S F S F SF SF Sc c c c

21

c c c c c c c c c c c c c c c c c c c c c c c cc c c c

1 2 3 4 5 6 7 8 9 10 20 41

F = FCCH S = SCH B = BCCH

LOG ICAL

CHANNEL

FCCH

Frequency

Correction

1 every 10 fram es

(46 m s)

OCCURRENCE

and/or USABLE BIT

RATE

as FCCH (46 m s), 8 TSafter

SCH

Synchro

BCCH

Broadcast

Control

1 TS every 4 consec. fram esevery51 fram es,

giving 456 usable bits

every 235 m s

-G eneral inform ation (system ) concerning the station:- Identity of operator, access authorized or not,

- O rganization of logical channels in the cell (paging...),

- Frequencies used, Frequency hopping...,

- Tim e-O uts applicable...

- Locking the m obile local oscillator on the exact frequency

- Roughly estim ating the position of the receive window

- Exact synchronization of receive window

- Decoding the Fram e Num ber(from 0 to 2,715,647)

RO LES and USES of INFORM ATIO N CARRIED



68/104


STRUCTURE of the M ULTIFRAM E in "TIM E SLOT" 0 (Non-com bined BCCH)

LOG ICAL

CHANNEL

RACH

Random

Access

O nlyuplink

OCCURRENCE

and/or USABLE BITRATE

These 2 sub-channels

share the "CCCH"

channel based on variable

rules according to cell and

operator

AG CHAccess

Grant

PCH

Paging

- used by the network to signal a call to a m obile:

Short form at identity, unam biguous in the cell

- used by them obile to request accessto the network

("Channel Request" m essage with m obile short form at identity)

- used by the network to acknowledge the access request andassign a dedicated channel to the m obile ("im m ediate

assignm ent" m essage with identity echo)


-

R = RACH

DO W NLINKf s b b b b C C C C

31 51 1211 2 3 4 5 6 7 8 9 10 20 41

f s f s f s f sC C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C -

(Multiframes of 51 frames)

f = FCCH s = SCH b = BCCH

f s

C C C C = CC CH (PCH or AGCH )

UPLINK

R R R RR R R R R R R RR R R R R R R RR R R R R R R RR R R R R R R RR R R RR R R RR R R R R R



69/104


- O ut of call signalling, such as location update, authentication,

transition to encrypted m ode, assignm ent of a traffic

channel...

SACCH

Slow

AssociatedControl

SDCCHStandalone

Dedicated

Control

STRUCTURE of the M ULTIFRAM E in "TIM E SLOT" 1

LOG ICAL

CHANNEL

8 TSs every 2x51 fram es,giving 456 bits / 235 m s

---> 1.94 kbit/s

OCCURRENCE

and/or USABLE BIT

RATE

4 TSs every 2x51 fram es,

giving 456 bits / 470 m s

---> 950 bit/s

- Non-urgent procedures (background), occurrence ~0.5

sec:m easurem ent reports, power m onitoring, tim ing advance,

+ Short M essage Service (SM S)


DO W NLINK

(M ultifram es of 51 fram es)

D = SDCCH A = SACCH

UPLINK

-

-- -

- -D0 D1 D2 D3 D4 D5 D6 D7

D0 D1 D2 D3 D4 D5 D6 D7

A0

A4

A1 A2 A3

A5 A6 A7

D0 D1 D2 D3 D4 D5 D6 D7

D0 D1 D2 D3 D4 D5 D6 D7 A0

A4

A1 A2 A3

A5 A6 A7

-

-- -

- -


70/104



71/104


0 1 2 3 4 5 6 7

TS

0 1 2 3 4 5 6 7

0 1 2 3 4 5 6 7

0 1 2 3 4 5 6 7

"Beacon" frequency

O therfrequencies

FCCH + SCH + BCCH + PCH + AGCH

uplink direction

downlink direction

RACH

TS 0 :

TS 1 : 8 SDCCH/8 + 8 SACCH/8 in each direction

other TSs: TCH (+ SACCH / FACCH) in each direction

BTS

Exam ples : Num ber of Frequencies Num ber of TCH Channels ERLANG S(form ula B, blocking 2% )

3 22 15

4 30 225 38 29



72/104


0 1 2 3 4 5 6 7TS

0 1 2 3 4 5 6 7

"Beacon" frequency

Other

frequency

FCCH + SCH + BCCH + PCH + AGCH + RACH + 4 SDCCH /4 + 4 SACCH/4TS 0 of beacon frequency:

other TSs: TCH (+ SACCH / FACCH)

BTS

STRUCTURE of the M ULTIFRAM E in "TIM E SLO T" 0 (Config. n 1: com bined BCCH) :

R = RACH

DO W NLINK (M ultifram es of 51 fram es)

F = FCCH S = SCH B = BCCH C = CC CH (PCH or AG CH )

UPLINK

F S B C F S F S F S -F SC C D0 D1 D2 D3 A0 A1

F S B C F S F S F S -F SC C D0 D1 D2 D3 A2 A3

R R R R R R R R R R R R R R R R R R R R R R R R R R RD3 A2 A3 D0 D1 D2

R R R R R R R R R R R R R R R R R R R R R R R R R R RD3 A0 A1 D0 D1 D2

Dn/An = SDCCH/SACCH/4

RADIO INTERFACE4.3.4 Tim ing Advance


73/104


BTS

M S

Presynchronized

BTSTx

Rx

Tx

RxM S1

TS i

TS i

T.A. m easured by BTS

Access Burstforward propagation tim e

BTSTx

Rx

Tx

RxM S1

TS iTS i

(after TA)

- TA

forward propagation tim e

return propagation tim e

RADIO INTERFACE4.3.5 Subscriber Paging


74/104


The NETW ORK know s the LOCATION AREA (LA) in w hich the m obile is

travelling.

An LA can cover m ore than one cell.

The PCH channel is used to signal a CALL to a m obile.

The sam e "Paging" m essage is transm itted to all cells in the area (shadedareas above).

Only a m obile in "IDLE" state (pre-synchronized) can respond to paging.

BSC

RADIO INTERFACE4.3.6 Access to the Network


75/104


An access request is always initiated by the M OBILE

(when a m obile is called, the "paging" procedure is used).

The RACH channel is used to transm it the "CHANNEL REQUEST" m essage.

The channel is called "random " since the m obile chooses the call TS

random ly.

This m eans that there is a risk of collision.

Collisions are resolved by retransm ission after pseudo-random delays.

M S1

M S5

M S2 M S3 M S4 M S4

M S5

RADIO INTERFACE4.3.7 Logical Channel Sum m ary


76/104


Abbreviation Nam e Type Role/Info carried Burst form at

Frequency Correction CHannel M P --> M S Frequency for synthesizer alignm ent Frequency

Synchronization CHannel M P --> M S Tim ing sync - Fram e N Sync

Broadcast Com m on CHannel M P --> M S Broadcast system inform ation Norm al

Random Access CHannel PP M S Subscriber paging (paging) Norm al

Access G rant CHannel PP --> M S SDCCH channel assignm ent (Im m .Ass) Norm al

Cell Broadcast Control CHannel M P --> M S Broadcast short m essages (SM S/CB) Norm al

Notification CHannel M P --> M S Accessibility notification (VGCS/VBS) Norm al

Dedicated

signalling

(out of call)

Standalone Dedicated Ctrl CH. PP Out of call signalling Norm al

Slow Associated Control CH. PP M easurem ents - P Contr. - Tim ing adv. Norm al

Traffic / Full Rate CHannel PP 13 kbit/s traffic Norm al

Traffic / Half Rate CHannel PP 5.6 kbit/s traffic (phase 2) Norm al

Slow Associated Control CH. PP M easurem ents - P Contr. - Tim ing adv. Norm al

Fast Associated Control CH. PP In call signalling (cycle stealing) Norm al

Fam ily

FCCH

SCHBCCH

Broadcast

CCCH

Dedicated

Traffic +

signalling

(during call)

RACH

PCH

AGCHCBCH

NCH

SDCCH

SACCHTCH/F

TCH/H

SACCH

FACCH

GSM (circuit switching)

RADIO INTERFACE4.3.7 Logical Channel Sum m ary


77/104


NCH

Abbreviation Nam e Type Role/Info carried Burst form at

Packet Broadcast Com m on CH. M P --> M S Broadcast system inform ation Norm al

Random Access CHannel PP M S Subscriber paging (paging) Norm al

Access G rant CHannel PP --> M S SDCCH channel assignm ent (Im m .Ass) Norm al

Notification CHannel M P --> M S Accessibility notification (VGCS/VBS) Norm al

Packet Data Transfer Channel PP Norm al

Packet Associated Control Ch. PP Norm al

Packet Tim ing Control Ch. PP Tim ing advance Norm al

Fam ily

PBCC

H

Broadcast

CCCH

pdch

PRACH

PPCH

PAGC

H

PDTCH

PACC

HPTCCH

Acknowledge - Power Control

User Data

GPRS

RADIO INTERFACE4.4.1 Radio Channel generation


78/104


ChannelEncoding

Speech

Digitizationand

Encoding

Interleaving

Burst

Form attingEncryption M odulation Transm ission

ReceptionDem odulationDecryptionBurst

Deform atting

De-

interleavingChannel

DecodingSpeech

Decoding

POW ER M O NITO RING

260 bits / 20 m s :13 kbit/s 22.8 kbit/s

(per channel)

270.8 kbit/sSpeech fram es :

(m odulated)

RADIO INTERFACE4.4.1 Radio Channel generation


79/104


Bit Rate on Um interface

GSM circuit-switched

Full Rate (FR) / Enhanced Full rate (EFR) speech: 13 Kbit/s

Half rate (HR) speech: 5.6 Kbit/s

Data transm ission: m axim um 14,4 Kbit/s

GSM packet-switched (GPRS) : 4 Coding Schem es

CS-1 : 9,05 Kbit/s (per TS)




RADIO INTERFACE4.4.2 Discontinuous Transm ission


80/104


Principles (M andatory in the m obile and on the BTS uplink path) :

DTX (Discontinuous Transm ission) : reduced rate transm ission (~ 500 bit/s)

during silences

VAD (Voice Activity Detection): M easurem ent of signal strength for detectingm om ents of "silence (neither speech nor tone) - adaptive-threshold FILTER

Com fort Noise Generation:

In receive m ode, reconstitution of background noise based on the

characteristics received in Silence Descriptor (SID) fram es, to avoid giving thereceiving user the im pression that the line has been cut off

S*

S S' S'S'S' S'S'S'S"

480 m s BTS

TRAU --> BTS

M S BTS

SPEECH

SILENCE

SID FRAM E

TRAU

RADIO INTERFACE4.4.3 GM SK M odulation


81/104


GM SK = Gaussian M inim um Shift Keying:

Principle close to offset quadri-phase shift keying

(OQ PSK) m odulation, obtained by convolution of

an M SK ram p of height/2 and width 1 bit, by aGaussian function: "gradual" 0-1 or 1-0 transitions of /2 :

PROPERTIES :

Gradual transitions avoid the need to filter signal harm onics which arevery weak

Spectrum efficiency of the order of 1 bit/Hertz

(270.8 kbaud/200 kHz)

M odulation spectrum :

==> To prevent catastophic interference,

it is essential to avoid using

adjacent frequencies in adjacent cells.

p/2

t

0 T 2T-T-2T

dB0

-10

-20

-30

-70

0 100 200 300 400-100-200 kHz

RADIO INTERFACE4.5.1 Frequency Hopping


82/104


" f "

"G AP" in frequency " f " reception

RADIO INTERFACE4.5.1 Frequency Hopping


83/104


N-frequency hopping groups can be defined for each TS (N>=4)

The overall system capacity rem ains unchanged (eg. : 32 m obiles on 4

frequencies)

0 1 2 3 4 5 6 7TS

"Beacon" frequency

O ther

frequencies

FCCH/ SCH/ BCCH/ CCCH

SDCCHNo Hopping

TS0 : Hopping over 4 frequencies TS3 : Hopping over 5 frequencies

RADIO INTERFACE4.5.2 Power Control


84/104


M easurem ent Ratios sent every 470 or 480 m s (SACCH occurrences) by M S Power Control algorithm run in the BSC (or BTS)

M odulation of the pow er transm itted by the BTS and m essage transm ission to the M S

(in SACCH)

Possible M ODULATION : 2 dB m ax. every 60 m sec,within a range from 6 to 21 x2 dB (DL) and optionally 15 x2 dB (UL):

8 W

20 m W

2 15

26 dB

0

13

39

dBm

pow er steps0

13

39dBm

19 17 31 31 29 dBm

tim e

60 m scontrols

Level

EXAM PLE for a portable M O BILE

2 W33 33 P m ax M S 2W

RADIO INTERFACE4.5.3 Space Diversity


85/104


In Receive M ode, 2 independent paths in the base station

A Discrim inator identifies the best signal.

PATH 1

PATH 2

RESULT



86/104


5 Interchanges over the Network

INTERCHANG ES OVER THE NETW ORKContents


87/104


5.1 GSM Num bers and Identities

5.1.1 GSM Subscribers: m ain types of identification

5.1.2 M obile Equipm ent identification

5.1.3 Geographic identification

5.2 BSS / NSS Protocols and Software M odules

5.2.1 General

5.2.2 Radio Interface (Um ) : Layer 3 : "RIL 3" protocol

5.2.3 GPRS protocols

5.3 Typical Sequence for an Originating Call

5.4 Level 3 GSM Procedures

5.4.1 Setting up the radio connection

5.4.2 Security Functions

5.4.3 M obile O riginating Call (M O)

5.4.4 M obile Term inating Call (M T)

5.4.5 Exam ple of an International Call

5.4.6 Location Updating

5.4.7 Change of Cell during the Call ("Handover")

INTERCHANG ES OVER THE NETW ORK5.1.1 GSM num ber and identities: Subscriber identifications

IM SI M S ISDN


88/104


IM SI M S - ISDN

( International M obile Subscriber Identity )

International Identity E212 com pliantNature

(M obile Station - Integrated Service Digital Netw ork n )

Directory Num ber ISDN type, E.164/E.213 com pliant

M CC M NC M SINH1 H2 x x x ........ x x x

M obileCountryCode

M obileNationalCode

M obile Subscriber Identity Num berincluding H 1 H2 = N of physical HLR

Form at

M eaning

N of digits

Exam ples

Characteristics

3 2 m ax 10

234

208 01

10

Stored in SIM m odule and AuC

CC NDCSN

M 1 M 2 x x x x x x x x

CountryCode

National

Code*Destination

Subscriber Num ber( national identity )

including M 1 M 2 identifying the logical HLR

(ZAB) (PQ)

1 to 3 2 to 4

44 802 Cellnet GSM44 385 Vodafone GSM44 956 M ercury DCS44 973 Hutchinson DCS

33

33

607/8

609

61 M C DU to 69 M C DU LYON

01 M C DU to 09 M C DU M ASSENA

11 xxxx to 3x xxxx LA FOURCHE

Allocated to an IM SI (by M M C) in the HLR

69 xx xx xx xx LYON

94 xx xx xx xx M ASSENA

?

France

U.K.

France Tlcom

SFR

total up to 15

* instead of identifying a geographic area, the NDC identifies an O PERATOR:

( national identity )NM SI

INTERCHANG ES OVER THE NETW ORK5.1.2 GSM num ber and identities: M obile Equipm ent identification


89/104


IM EI / IM EISV

( International M obile Equipm ent Identity )

TAC FAC SNR SP

Type Approval CodeFinal Assem bly Code

Serial Num beR

(SPare)

Stored in the Equipm ent (Term inal)

Used to replace the IM SI or TM SI if they cannot be used

(exam ple : em ergency calls with no SIM card) or at the network's request (m aintenance)

Can be used to update the EIR database (if there is one)

( International M obile Equipm ent Identity and Software Version num ber) (Phase 2+)

TAC FAC SNR SVN

Software Version Num ber

IM EI

:

IM EISV:

INTERCHANG ES OVER THE NETW ORK5.1.3 GSM num ber and identities: Geographic identification


90/104


LAI: Location Area Identification

M CC = M obile Country Code

M NC = M obile Network Code

LAC = Location Area Code

Use of LAI:

Paging

Location Area Updating

Security

CGI Cell Global Identification

CI = Cell Identifier

M CC M NC LAC CI

LAI

CGI

INTERCHANG ES OVER THE NETW ORK5.1.3 GSM num ber and identities: Geographic identification


91/104


RAI: Routing Area Identification

M CC = M obile Country Code

M NC = M obile Network Code

LAC = Location Area Code

RAC = Routing Area Code

Use of RAI:

Paging

Routing Area Updating

M CC M NC LAC RAC

RAI

For GPRS:

INTERCHANG ES OVER THE NETW ORK5.2.1 BSS / NSS Protocols and Software M odules: general


92/104


S.C.1S.C.1 S.C.1S.C.1

SCCP

M TP 3

M TP 2

S.C.1

SCCP

M TP 3

M TP 2

S.C.1

TCAP

M AP

TCAP

M AP

SCCP

M TP 3

M TP 2

S.C.1

DTAP

SCCP

M TP 3

M TP 2

S.C.1

DTAP

LAPDLAPDm LAPD

SS (SM S)SS (SM S)

BSSM AP

M M

CC

BSSM APRR

RR

RR' BTSMBTSM

LAPDm

(SM S)

SSCC

M M

(Relays)

M S BTS BSC M SC / VLR NSS

(eg. : HLR)

Um A bis A (D)

1

2

3

(Relays)

INTERCHANG ES OVER THE NETW ORK5.2.2BSS / NSS Protocols and Software M odules: Radio Interface


93/104


-Call handling and routing

- DTM F facilities

- Access to Supplem entary

Services

- Short M essage Service

-Paging m anagem ent

- Ciphering m ode m anagem ent

- Frequency redefinition

- Dedicated channel assignm ent

- Handover m anagem ent- M easurem ents and pow er control

Radio Interface Layer 3 protocol

Protocol

Discrim inator

RR Radio Resource

M anagem ent

M eaning

M M M obility M anagem ent-Paging m anagem ent

- Ciphering m ode m anagem ent

- Frequency redefinition

- Dedicated channel assignm ent

Function

Call Control

Supplem entary Services

Short M essage Service

CC

SM S

SS

Entities

M S - BSC

(and BTS)

M S -

M SC / VLR

M S - M SC

(+ HLR)

(+ SM S-C)

INTERCHANG ES OVER THE NETW ORK5.2.3 BSS / NSS Protocols and Software M odules: GPRS protocols

GPRS operation:basicprocedures


94/104


IP NetworkBSS

SGSNM S1

GGSN1

GGSN2

PDN1

PDN2

LLC

TLLI1

Attachm ent

TID2

= IMSI + session2

GTP

TID1

= IMSI + session1

Opening

Session(s)

GPRS operation: basic procedures


IP overview


95/104


ipip ipip ip

http httpftp ftpsm tp sm tpgtp gtp

GGSNSGSN

1tcp1tcp

wap wap

IP overview

Routers

IP network

Client Server

INTERCHANG ES OVER THE NETW ORK5.2.3 BSS / NSS Protocols and Software M odules: GPRS Protocols


96/104


GTPSNDCP SNDCP

BSSGP

LLC

M S BSS SGSN GGSN

Um Gn

Layer M odel for Transm ission plan (GPRS)

relay

L1 bis

Fram e

Relay

L1

L2

L1

L2

PhysicalLayer

M AC

L1 bis

Fram e

Relay

PhysicalLayer

M AC

RLC

LLC

Gb

GTP

IP

UDP &

TCP

IP / X25Appli

BSSG

PRLC

IP

UDP &

TCP

IP / X25

LayerM odelforTransm ission plan (GPRS)(2)



97/104


Layer M odel for Transm ission plan (GPRS) (2)

Header Data

Header Data

LLC

PHYSICAL

CRC CRC CRCRLC M AC

IP/X25

SNDCP

Division of the SDU in 2 blocks

Com pression of each part

Label added for each block

LLC EncapsulationCRC

RLC Encapsulation

LLC fram e splitted

into blocks

Header

= < 1520 BytesHeader

Channel Coding CS1 to CS4

Block 1Block 2Block 3Block 4Block 5Block 6Block 7Block 8

Block 1 Block 2 Block 3 Block 8

CRCHeader

Header



98/104


GTPGM M

BSSGP

LLC

M S BSS SGSN GSN

Um Gn

Layer M odel for Signalling plan (GPRS)

relay

L1 bis

Fram e

Relay

L1

L2

L1

L2

L1 RF

M AC

L1 bis

Fram e

Relay

L1 RF

M AC

RLC

LLC

Gb

IP

UDP

SM

BSSG

PRLC

IP

GSM S

UDP

GM M

SMG

SM S

GTP

GSN

INTERCHANG ES OVER THE NETW ORK5.3 Typical Sequence for an Originating Call


99/104


M O BILE GSM NETW ORK

CHANNEL REQUEST

IM M EDIATE ASSIG NM ENT

CM SERVICE REQUEST

AUTHENTICATION REQ UEST

AUTHENTICATION RESPO NSE

CIPHERING M O DE CM DCIPHERING M O DE CO M PLETE

SET UP

CALL PRO CESSING

ASSIGNM ENT CM D

ASSIGNM ENT CO M

ALERTING

CONNECT

CO NNECT ACK

SET-UP of anRR CO NNECTION (M O)

SERVICE INDICATION

AUTHENTICATIO N

TRANSITIO N to CIPHERING M ODE

START of CALL

TRAFFIC CHANNEL

CALL CO NFIRM ATION

CALL ACCEPTED

ASSIGNM ENT

PSTN or ISDN

INTERCHANG ES OVER THE NETW ORK5.4.1 Level 3 GSM procedures: Setting up the radio connection

U


100/104


SDCCH N

M M CM _SERVICE REQ UEST

SDCCH N

RACH

M SCHANNEL REQUEST

IM M EDIATE ASSIGN.

BTS BSC M SC

Um A bis A

CHANNEL REQUIRED

ASSIG NM ENT of anSDCCH Channel

CHANNEL ACTIV.

ACTIVATION of

Channel indicated CHANNEL ACTIV. ACK

AG CH

CONNECTION to theSDCCH Channel

SDCCHSABM ESTABLISH INDIC.

SCCP CONNECT REQUEST

SCCP CO NNECT CO NFIRM

T3101

T9105

IM M . ASSIG N. CM D

RR

RR


RR

BTSM

BTSM

BTSM

SDCCH UA



INTERCHANG ES OVER THE NETW ORK5.4.2 Level 3 GSM procedures: Security Functions


101/104


Authentication

Checks that the M obile Station is the required station and not an intruder

Ciphering

All Inform ation (Signalling, Speech and Data) is sent in cipher m ode, to avoid

m onitoring and intruders (who could analyze signalling data)

Tem porary Identification

Each tim e the network is accessed for whatever reason, a different num ber isused to identify a subscriber, so that the subscriber identity cannot be used by

an intruder: On each access operation a new tem porary num ber is sent in

cipher m ode, and provides identification for the next access operation.



102/104


SIM card

A3

AuCRadio Channel

A8

Ki Ki

Random num ber selection

A3

A8

A3 A3

A8A8

A5A5

= ?

Identification key (128 bits)

RAND (128 bits)

RAND

Signed ref. (32 bits) SRES SRES

Cipher com m and

OK

Kc : Cipher key

for the call (64 bits)

Kc

Speech - Data - Signalling Speech - Data - Signalling Ciphered data

Ciphering/Deciphering Ciphering/Deciphering

BTS

A5A5



103/104


MS BTS HLRMSC / VLR OMCAuC

SIM card

IMSI

KiA3A8

RAND

SRES

Kc

Ciphering

Function

A5

Ciphering

FunctionRANDSRES

Kc

RANDSRES

Kc

Kc

= ?

TripletsTriplet

Generation

RAND

Ki

KiIMSI

A4Ki

IMSI

(ciphered)

A4

A2

SpeechDataSign

SpeechDataSign

(ciphered)

RAND

SRES

A8

A3

Ki

IMSI

IMSIA8

A3

Ki

IMSIIMSITMSI

A5 Kc

TMSI

A5

Kc

INTERCHANG ES OVER THE NETW ORK5.4.3 Level 3 GSM procedures: M obile Originating Call


104/104


M OBILE GSM NETW ORK

CHANNEL REQUEST

IM M EDIATE ASSIG NM ENT

CM SERVICE REQUEST

AUTHENTICATIO N

CIPHERING

SET UP

ASSIGNM ENT CM D

ASSIGNM ENT CO M

ALERTING

CONNECT

CO NNECT ACK

VEA : Very Early Assignm ent :

CALL CO NFIRM ATION

CALL ACCEPTED

or SET UP if VEA

ASSIGNM ENT CM DASSIGNM ENT CO M 1/2 O ACSU :

ASSIGNM ENT CM D

ASSIGNM ENT CO MO ACSU com plete

Im m ediate assignm ent of a TCH :

No authentication or ciphering

(Signalling carried on FACCH)

EA : Early Assignm ent :

TCH allocated BEFO RE call confirm ation

om itted if VEA

TCH allocated after called party ringing

TCH allocated after called party answ er"Queuing"

PSTN or ISDN

L1 - GSM Alcatel Introduction

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Transcript of L1 - GSM Alcatel Introduction