gsm

INDC Juin 2000 1

INTRODUCTION TO THE Alcatel 900/1800 GSM NETWORK

1 –GSM NETWORK ARCHITECTURE

INDC Juin 2000 2

GSM NETWORK ARCHITECTURE

CONTENTS

1.1 General specifications

1.2 Interchanges over the network

INDC Juin 2000 3

1.1 GENERAL SPECIFICATIONS

GSM 900 AND DCS 1800

� GSM: GLOBAL SYSTEM FOR MOBILE COMMUNICATION - Pan-European standard for communication with mobiles, already adopted by more

than 60 countries and now the worldwide reference for mobile radio networks. Since 1995 (phase 2), this standard harmonizes the 900 MHz GSM system and the 1800 or 1900 MHz DCS system.

� GSM 900: - Mobile radio system based on the GSM standard, designed for urban and rural

applications (macro-cells) and currently operating in two 25 MHz frequency bands around 900 MHz.

� DCS 1800: DIGITAL CELLULAR SYSTEM - Mobile radio system derived from the GSM 900 (same basic principles), designed for

urban applications (micro-cells) and currently operating in two 75 MHz frequency bands around 1800 MHz.

� DCS 1900: - North and South American variant of the DCS 1800, operating in two frequency bands

around 1900 MHz.

INDC Juin 2000 4


GENERAL CONCEPTS: PLMN AND MOBILES

� The PLMN is an ACCESS NETWORK � The SUBSCRIBERS are MOBILES ==> RADIO RESOURCES (RR) management MOBILITY management (MM)

ISDN

PSTN

PSPDN

PLMN

PLMN = Public Land Mobile Network

INDC Juin 2000 5


GENERAL CONCEPTS: CELLULAR COVERAGE

downlink

uplink VIP

GSM antenna

� Propagation limits performance � Radio resources are limited ==> multiplication of cells: limits � To increase spectrum efficiency, technical fixes

are introduced: - POWER MONITORING (=>Ø interference level) - DISCONTINUOUS TRANSMISSION (=>Ø interference level) - FREQUENCY HOPPING (to limit fading) - HANDOVER ASSISTED by mobile: systematic measurements ( => Quality of service always higher than a given threshold) � Definitions: - UPLINK: Mobile -> Base station - DOWNLINK: Base station -> Mobile

INDC Juin 2000 6


GSM ARCHITECTURE: TYPES OF MOBILE STATION (MS)

SIM card

(including TAF)

TA

R

S

MT1

MT0

MT2

TE1

TE2

TE2

ISDN terminalBSS

Um

"plug-in" SIM

ISDN

(Conventional terminal -

Modem interface)

ISDN concepts GSM concepts

MT = Mobile Termination

TE = Terminal Equipment

TA(F) = Terminal Adaptor (Function)

INDC Juin 2000 7


GSM ARCHITECTURE : PLMN ELEMENTS

Base station system BSS

BTS Basic Transceiver Station

BSC Base Station Controller

Network and switching system

MSC 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]

BSC

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BSC

MSC

VLR HLR AuC EIR

PSTN,ISDN...

OMCOMC

NMC

X.25 links

GSM interfaces

Voicemail Server

SM-SC

MS(Mobile Station)

BSS(Base Station System)

NSS(Network & Switching System)

OSS(Operation & maint. Sub System)

GCR

INDC Juin 2000 8


GSM ARCHITECTURE : BASE STATION SYSTEM (BSS)

MAIN FUNCTIONS:

BTS

∇ PHYSICAL CHANNEL MANAGEMENT (on Radio channel)

BSC

∇ MANAGEMENT OF INTERFACES WITH NSS & OSS

∇ MANAGEMENT OF RADIO "LOGICAL" CHANNELS

∇ BTS MONITORING

CBC : Cell Broadcast Centre (optional)

∇ Buffer STORAGE and Generation of CELL BROADCAST SHORT MESSAGES (phase 2)

BSC

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BSC

NSS CBC

INDC Juin 2000 9


GSM ARCHITECTURE : NETWORK AND SWITCHING SYSTEM (NSS)

MSC

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 STORES: Identities - Directory numbers - Services subscribed + Approx. location (VLR)

VLR � LOCAL 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

INDC Juin 2000 10


GSM ARCHITECTURE : OPTIONAL EQUIPMENT (NSS)

MSC

SM-SC

EIR

BSS

VoiceMail Server

GCR

MAIN FUNCTIONS:

EIR ∇ Mobile EQUIPMENT DATABASE

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

Voice Mail Server ∇ (not specified in GSM standard)

SM-SC ∇ SHORT MESSAGE Service Center message storage during subscriber unavailability

GCR : Group Call Register (optional) ∇ VOICE CALL GROUP SERVER (new services in phase 2+, PMR type)

INDC Juin 2000 11


GSM ARCHITECTURE : OPERATION AND MAINTENANCE SUBSYSTEM (OSS)

NSS

OMC-M or SOMC-R

NMC

BSS

OMC OMC-R --> Radio BSS management OMC-NSS --> Mobile NSS management � CONFIGURATION MANAGEMENT � FAULT HANDLING � PERFORMANCE MANAGEMENT � SECURITY MANAGEMENT � BILLING

NMC (optional) � Higher level NETWORK MANAGEMENT (TMN network)

INDC Juin 2000 12


GSM INTERFACES AND PROTOCOLS

Interfaces Protocols

BTS

BTS

BTS

BTS

BTS

BTS

BTS

BSC

MSC

VLR HLR AuC EIR

PSTN,ISDN...

VLR

MSCE

B C

D

F

G

H

GCR

I

BSC

Um Abis

A

B C D E F G H I

PSTN ISDN

Radio GSM-specific BTS - BSC (ISDN type)

BSC-MSC (SS7 basic)

MSC-VLR | (SM-G)MSC-HLR | HLR-VLR | (SM-G)MSC-MSC | (SS7 basic) MSC-EIR | VLR-VLR | HLR-AuC | MSC-GCR |

MSC-PSTN (SS7 basic) MSC-ISDN

LAPDm LAPD

+ BSSAP

+ MAP

+ TUP or ISUP

INDC Juin 2000 13


GSM ARCHITECTURE : POSITION OF TRANSCODER (TRAU)

BTS BSC MSC VLR

TRAU

BTS BSC MSC VLRTRAU

BTS BSC MSC VLRTRAU

Abis interface A interface

16 kbit/s transmission

64 kbit/s transmissionKEY :

INDC Juin 2000 14

1.2 INTERCHANGES OVER THE NETWORK

GSM/DCS SUBSCRIBERS : MAIN TYPES OF IDENTIFICATION

IMSI MS - ISDN

( International Mobile Subscriber Identity )

International Identity E212 compliantNature

( Mobile Station - Integrated Service Digital Network n° )

Directory Number ISDN type, E.164/E.213 compliant

MCC MNC MSINH1 H2 x x x ........ x x x

Mobile Country

Code

Mobile NationalCode

Mobile Subscriber Identity Number including H1 H2 = HLR Number

Format

Meaning

N° of digits

Examples

Characteristics

3 2 max 10

234

208 01

10

Stored in SIM module and AuC

CC NDC SNM1 M2 x x x x x x x x

CountryCode

National

Code*Destination

Subscriber Number ( national identity )

including M1 M2 identifying the HLR

(ZAB) (PQ)

1 to 3 2 to 4

44 802 Cellnet GSM44 385 Vodafone GSM44 956 Mercury DCS44 973 Hutchinson DCS

33

33

607/8

609

61 MC DU to 69 MC DU LYON01 MC DU to 09 MC DU MASSENA

11 xxx to 3x xxx LA FOURCHE

Allocated to an IMSI (by MMC) in the HLR

69 xx xx xx xx LYON94 xx xx xx xx MASSENA

?

France

U.K.

France Télécom

SFR

total up to 15

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

( national identity )NMSI

INDC Juin 2000 15


MOBILE EQUIPMENT IDENTIFICATION

IMEI

( International Mobile Equipment Identity )

TAC FAC SNR SP

Type Approval Code

Final Assembly Code

Serial NumbeR (SPare)

� Stored in the Equipment (TERMINAL)

� Used to replace the IMSI or TMSI if they cannot be used (example : emergency calls with no SIM card) or at the network’s request (maintenance)

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

INDC Juin 2000 16


GEOGRAPHIC IDENTIFICATION

MCC MNC LAC CI

LAI

CGI

LAI

Location Area Identification

� Identifies a LOCATION AREA (LA)* :

- MCC, MNC : Country + Network Codes (as IMSI) [eg.: 208.01 for France Télécom] - LAC : Location Area Code : N° of the "LA" in the network (up to 2 octets, at the operator's discretion - values 1 to 65 536)

CGI

Cell Global Identification

� Identifies a CELL (BTS) unambiguously - CI : Cell Identifier (2 octets) : unique in a LA

* Notes

� An LA can contain more than one cell, which can be managed by more than one BSC, but are dependent on the same MSC

Uses

� for "PAGING" (in which cells is a subscriber to be paged?) � for Location Updating (Change of LA ⇒ Location update) � for SECURITY (complete TMSI, unambiguous = TIC + LAI)

INDC Juin 2000 17

1.2 INTERFACES AND SIGNALLING PROTOCOLS

BSS / NSS PROTOCOLS and SOFTWARE MODULES : GENERAL

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

SCCP

MTP 3

MTP 2

S.C.1

SCCP

MTP 3

MTP 2

S.C.1

TCAP

MAP

TCAP

MAP

SCCP

MTP 3

MTP 2

S.C.1

DTAP

SCCP

MTP 3

MTP 2

S.C.1

DTAP

LAPDLAPDm LAPD

SS (SMS)SS (SMS)

BSSMAP

MM

CC

BSSMAPRR

RR

RR’ BTSMBTSM

LAPDm

(SMS)SSCC

MM

(Relays)

MS BTS BSC MSC / VLR NSS(eg. : HLR)

Um A bis A (D)1

2

3

(Relays)

INDC Juin 2000 18

1.2 INTERFACES AND SIGNALLING PROTOCOLS

RADIO INTERFACE (Um) : LAYER 3 : "RIL3" PROTOCOL

� "RIL 3" protocol (Radio Interface Layer 3) : incorporates three software subassemblies which can be distinguished by the value of a Protocol Discriminator (PD) field : RR, MM, CC/SS/SMS :

� In addition, in "RR" messages, a Transaction Identifier (TI) field is used to manage a number of simultaneous transactions

PD Meaning Resource/Dest. Functions

RR Radio Resource Management MS - BSC (and BTS) � Paging management � Ciphering mode management � Frequency redefinition � Dedicated channel assignment � Handover management � Measurements and power monitoring

MM Mobility Management MS - MSC / VLR � Authentication/Identification procedures � Location update � Attach/detach IMSI � Connection management

CC /

SS /

SMS

Call Control

Supplementary Services

Short Message Service

MS - MSC

(+ HLR)

(+ SMS server)

� Call handling and routing � DTMF facilities

� Access to Supplementary Services

� Short Message Service

INDC Juin 2000 19


TYPICAL SEQUENCE for an ORIGINATING CALL ("MO")

MOBILE GSM NETWORK

CHANNEL REQUEST

IMMEDIATE ASSIGNMENT

CM SERVICE REQUEST

AUTHENTICATION REQUEST

AUTHENTICATION RESPONSE

CIPHERING MODE CMD

CIPHERING MODE COMPLETE

SET UP

CALL PROCESSING

ASSIGNMENT CMD

ASSIGNMENT COM

ALERTING

CONNECT

CONNECT ACK

SET-UP of anRR CONNECTION (MO)

SERVICE INDICATION

AUTHENTICATION

TRANSITION to CIPHERING MODE

START of CALL

TRAFFIC CHANNEL

CALL CONFIRMATION

CALL ACCEPTED

ASSIGNMENT

PSTN or ISDN

INDC Juin 2000 20


RADIO CONNECTION (RR) SET-UP PROCEDURE

MSCHANNEL REQUEST

IMMEDIATE ASSIGN.

BTS BSC MSC

Um A bis A

CHANNEL REQUIRED

ASSIGNMENT of anSDCCH Channel

CHANNEL ACTIV.SDCCH N°

ACTIVATION ofChannel indicated

CHANNEL ACTIV. ACK

RACH

AGCH

CONNECTION to theSDCCH Channel

SDCCH N°

SDCCH

SDCCH

SABM

UA

ESTABLISH INDIC.SCCP CONNECT REQUEST

SCCP CONNECT CONFIRM

T3101

T9105

IMM. ASSIGN. CMD

RR

RR

CM_SERVICE REQUESTMM

CM_SERVICE REQUESTMM

CM_SERVICE REQUESTMMCM_SERVICE REQUESTMM

RR

BTSM

BTSM

BTSM

INDC Juin 2000 21


SECURITY PROCEDURES : GENERAL

� AUTHENTICATION

� CHECKS that the MOBILE STATION is the required station and not an intruder

� CIPHERING

� ALL INFORMATION (Signalling, Speech and Data) is SENT in cipher mode, to avoid monitoring and intruders (who could analyze signalling data)

� TEMPORARY IDENTIFICATION

� Each time the network is accessed for whatever reason, a DIFFERENT NUMBER is used to identify a SUBSCRIBER, so that the subscriber identity cannot be used by an intruder: On each access operation a new temporary n° is sent in cipher mode, and provides identification for the next access operation.

INDC Juin 2000 22


(continued) SECURITY PROCEDURES : MECHANISMS and VARIABLES

SIM card

A3

AuCRadio Channel

A8

Ki Ki

Random number selection

A3

A8

A3 A3

A8A8

A5 A5

= ?

Identification key (128 bits)

RAND (128 bits)

RAND

Signed ref. (32 bits) SRES SRES

Cipher command

OK

Kc : Cipher key

for the call (64 bits)

Kc

Speech - Data - Signalling Speech - Data - SignallingCiphered data

Ciphering/Deciphering Ciphering/Deciphering

BTS

A5A5

INDC Juin 2000 23


(continued) SECURITY PROCEDURES : IMPLEMENTATION

MS BTS HLRMSC / VLR OMCAuC

SIM card

IMSIKiA3A8

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

A8A3Ki

IMSI

IMSIA8A3Ki

IMSIIMSITMSI

A5 Kc

TMSI

A5

Kc

INDC Juin 2000 24


ORIGINATING CALL (M.O.) : "EARLY ASSIGNMENT" and "OFF-AIR CALL SET-UP"

MOBILE GSM NETWORK

CHANNEL REQUEST


CM SERVICE REQUEST

AUTHENTICATION

CIPHERING

SET UP

ASSIGNMENT CMD

ASSIGNMENT COM

ALERTING

CONNECT

CONNECT ACK

VEA : Very Early Assignment :

CALL CONFIRMATION

CALL ACCEPTED

PSTN or ISDN

or SET UP if VEA

ASSIGNMENT CMD

ASSIGNMENT COM1/2 OACSU :

ASSIGNMENT CMD

ASSIGNMENT COMOACSU complete

Immediate assignment of a TCH :

No authentication or ciphering(Signalling carried on FACCH)

EA : Early Assignment :TCH allocated BEFORE call confirmation

omitted if VEA

TCH allocated after called party ringing

TCH allocated after called party answer"Queuing"

INDC Juin 2000 25


(continued) ORIGINATING CALL SET-UP PROCEDURE (Mobile Originating) [1/2]

CHANNEL ACTIV.

DATA REQUEST

MS BTS BSC MSC/VLR

A bis A

PSTN

CALL PROCEEDING

DATA INDICATION

SCCP DATA

SCCP DATASET - UP

ASSIGNMENT CMD

PHYS. CTX REQ. SCCP DATACIC selection

AUTHENTICATION

CIPHERING

CHANNEL REQUEST

IMMEDIATE ASSIGN.

RACH

AGCH

SDCCH N°

SDCCH

Ciphered

SABM

UAESTABLISH INDIC. SCCP CONNECT REQUEST


SDCCH

PHYS. CTX CONF. TCH allocation

TCH

CHANNEL ACTIV. ACK

DATA REQUEST

Assignment Cmd

TCH

T3107RELEASE REQ * Local End

Um

RR

RR

CM Serv. Req.MMCM Serv. Req.MM

CM Serv. Req.MM

CC

CC

Set - UpCC

Call Proceeding.CC Call Proceeding.CC

Set - UpCC

Assignment RequestBSSMAPBTSM

BTSM

BTSM

BTSM

RR

RR

* if no answer from MS

IAMISUP

MIF)( or SSUTR2

INDC Juin 2000 26

1.2 INTERCHANGES WITHIN THE NETWORK

(continued) MOBILE ORIGINATING CALL SET UP PROCEDURE [2/2]

DATA REQUEST

MS BTS BSC MSC/VLR

UmA bis A

PSTN

ALERTING

DATA INDICATION

SSCS DATA

SSCS DATAASSIGNMENT COMPL.

RF CHANNEL REL.

SSCS DATA

Called P. ringing

FACCHSABM

UA

ESTABLISH INDIC.

Alerting

Assign. compl.

RF CHANNEL REL. ACK

Assign. compl.

MIF

Alerting

DATA REQUESTCONNECTSSCS DATAConnect Connect

ACF

RIU Off-hooking

DATA IND.CONNECT ACK Connect Ack

Connect Ack

CONVERSATION PHASE

INDC Juin 2000 27


TERMINATING CALL (M.T.) : ROUTING and Use of MSRN

� Called party MS-ISDN number � Detection of a mobile n° ⇒ call directed to PLMN concerned � HLR interrogation : transmission of mobile MS-ISDN � VLR interrogation : transmission of mobile MS-ISDN and IMSI � Temporary routing N° allocation by VLR : MSRN (roaming number) � Return of MSRN to the GMSC � Call rerouted to the visited MSC After VMSC-VLR dialogue, TMSI-based subscriber paging

GMSC

PSTN

VMSC

VLR

HLR

Visited PLMN

Origin PLMN

1

2

3

6

4

5

7

8

TUPmessages messages

MAP

INDC Juin 2000 28


(continued) TERMINATING CALL SET-UP (M.T.) ("EARLY ASSIGNMENT")

MOBILE GSM NETWORK

CHANNEL REQUEST


PAGING RESULT



CIPHERING MODE CMD


SET UP

CALL CONFIRMED

ASSIGNMENT CMD

ASSIGNMENT COM

ALERTING

CONNECT

CONNECT ACK

SET-UP of anRR CONNECTION (MT)

SERVICE INDICATION

AUTHENTICATION

TRANSITION to CIPHERING mode

START OF CALL

TRAFFIC CHANNEL

CALL CONFIRMATION

CALL ACCEPTED

ASSIGNMENT

PSTN or ISDN

PAGING REQUEST

INDC Juin 2000 29


TERMINATING CALL (M.T.) : INTERNATIONAL CALL

GMSC

PSTN

VMSCVLR

HLR

Visited PLMN

Called party

interrogation

origin PLMN

COUNTRY 1COUNTRY 2

COUNTRY 3

Incoming C.I.

Incoming C.I.

Outgoing C.I.

Outgoing C.I.

International SCCPGateways

INDC Juin 2000 30


LOCATION UPDATE PROCEDURES

� GENERAL

� This procedure is always initiated by the MOBILE station and involves providing the VLR (and HLR if required) with its current position,

� The HLR determines the ADDRESS of the visited VLR,

� The visited VLR stores the Location Area (LA),

� The LA n° (LAI) received is updated dynamically in SIM non-volatile memory.

� NORMAL LOCATION UPDATE

� When the mobile is switched on without having stored the LAI (eg.: initial use of SIM),

� When the mobile is switched on in a different LA from the LA stored in the SIM,

� When the pre-synchronized mobile moves from one LA to another (same or different VLR).

� PERIODIC LOCATION UPDATE

� When the SIM internal counter overflows and is incremented automatically when the mobile is switched on.

INDC Juin 2000 31


(continued) LOCATION UPDATE PROCEDURE : PRINCIPLE

MOBILE GSM NETWORK

CHANNEL REQUEST


LOCATION UPDATE REQUEST



CIPHERING MODE CMD


LOCATION UPDATE ACCEPTED

TMSI REALLOCATION COMPLETE

CHANNEL RELEASE

RR CONNECTION (MO)SET-UP of an

SERVICE INDICATION

AUTHENTICATION

TRANSITION to CIPHERING MODE

ALLOCATION of a

RR CONNECTION RELEASE

NEW TEMPORARY N°

TMSI

INDC Juin 2000 32


(continued) INTRA MSC/VLR LOCATION UPDATE PROCEDURE

CHANNEL REQUEST

IMMEDIATE ASSIGN.

CHANNEL REQUIRED

CHANNEL ACTIV.

CHANNEL ACTIV. ACK

RACH

AGCH

SDCCH SABM

UA

ESTABLISH INDIC.SCCP CONNECT REQUEST


IMM. ASSIGN. CMD

MS BTS BSC MSC

Um A bis A

VLR

SCCP DATADATA REQUESTLOCATION UPDATE ACC.

TMSI

TMSI REALLOC COMPLETEDATA INDICATION SCCP DATA

HLR

UPDATE LOCATION AREAUPDATE LOCATION

UPDATE LOCATION ACC

INSERT SUBSCR. DATA

LOC. AREA UPD. ACC.INSERT SUB. DATA ACK

TMSI Alloc.

RR

RR

MM

Loc. Upd. Req.MM

Loc. Upd. Req.MMLoc. Upd. Req.MM

RR

BTSM

BTSM

BTSM

Loc. Upd. Req.MM

MAPMAP

MAP

MAP

MAPMAP

Loc. Upd. Acc.MMLoc. Upd. Acc.MM

MM

TMSI Realloc. compl.MMTMSI Realloc. compl.MM

INDC Juin 2000 33


"HANDOVER" (CHANGE OF CELL DURING THE CALL) IN THE GSM SYSTEM

� 3 PHASES :

� a) Identification of requirement

� b) Selection of new cell

� c) Handover execution � MOBILE :

� Continuous Quality and Received power monitoring

� Continuous adjacent cell monitoring (power)

� Transmission of measurement reports on the SACCH channel to the BTS connected (every 0.5 s)

� NETWORK :

� The BTS measures the Quality and received power from the mobile

� The BSC runs the power monitoring and handover central algorithm

� The BSC controls the handover operation � HANDOVER TYPES :

� Internal (within the same BTS) if there is uplink or downlink interference

� Synchronized / non-synchronized

� Intra-BSC / Inter - BSC, Intra - MSC / Inter - MSC (first and subsequent)

INDC Juin 2000 34


(continued) CASE 1 : INTRA - MSC, INTRA - BSC HANDOVER

PSTN

MSC / VLR

MSC / VLR

MSC / VLR

BSC

BSC

BSC

BSC

BTS 1

BTS 2

INDC Juin 2000 35


(continued) CASE 1 : INTRA - BSC HANDOVER

MEASUREMENT REPORT

HANDOVER COMMAND

CHANNEL ACTIV.

CHANNEL ACTIV. ACK

SACCH

SABM

UAESTABLISH INDIC.

MS BTS 1 BSC MSC

UmA bis A

SCCP DATA

DATA REQUEST

DATA INDICATION

PSTN

Handover Cmd

H.O. Performed

Handover. compl.

Internal Handover decision

BTS 2

SACCH

on TCH

(RELEASE REQUEST) Local End

HANDOVER ACCESSHANDOVER DETECTION

PHYSICAL INFO

HANDOVER COMPLETE

Changeover to new channel

Release of old channel

T8

RF CHANNEL RELEASE

RF CHANNEL RELEASE ACK

RRMEASUREMENT REPORT

MEASUREMENT REPORTMEASUREMENT REPORTRR

BTSM

BTSM

RRRR

FACCH

Accessburst

RR

RR

FACCH

RR

BTSM

BTSM

BSSMAP

RR

INDC Juin 2000 36


(continued) CASE 2 : INTRA - MSC , INTER - BSC HANDOVER

PSTN

MSC / VLR

MSC / VLR

MSC / VLR

BSC 1

BSC 2

BSC

BSC

BTS 2

BTS 1

INDC Juin 2000 37


(continued) CASE 3 : FIRST INTER - MSC HANDOVER

PSTN

MSC / VLR 1

MSC / VLR 2

MSC / VLR

BSC

BSC 1

BSC 2

BSC

BTS 2

BTS 1

INDC Juin 2000 38


(continued) CASE 4 : SUBSEQUENT INTER - MSC HANDOVER

PSTN

MSC / VLR 1

MSC / VLR 2

MSC / VLR 3

BSC

BSC

BSC 1

BSC 2

BTS 1

BTS 2

INDC Juin 2000 39

INTRODUCTION TO THE Alcatel 900/1800 GSM NETWORK

2 – Alcatel GSM 900/1800 SOLUTION

INDC Juin 2000 40

Alcatel GSM 900/1800 SOLUTION

CONTENTS

1 � OVERALL INFRASTRUCTURE

2 � BASE STATION SYSTEM (BSS)

3 � NETWORK AND SWITCHING SUBSYSTEM (NSS)

4 � FUNCTIONS PROVIDED

5 � OPERATION AND MAINTENANCE (OMC)

6 � VALUE-ADDED SERVICES

7 � INTELLIGENT NETWORK SERVICES

INDC Juin 2000 41


1 OVERALL INFRASTRUCTURE

� Base Station System

• BSCs and BTSs with different configurations (chained sectored, star),

• OMC-R.

� Network and Switching Subsystem

• MSC, VLR, HLR, AUC, EIR, IWF,

• OMC-NSS,

• Value-added services: voice messaging, SM-SC,

• Sales management.

� Transmission Part

• Echo canceller, code converters, sub-multiplexers.

INDC Juin 2000 42


1 (continued) TOTAL INFRASTRUCTURE

BTSBSC

TC

"A" Interface

S/Mux

Alcatel 1000 E10SSP

Callprocessing

Echocanceller

IWF

PSTN/

ISDN

VoiceMailbox

SMS

EIR

HLR

AUC

NetworkSS7

VLRRCP

OMC-R OMC-NSS

Terminals

Operator terminals

Mobile radiofunctions

SalesManagementBilling

centreSubscriber

administrationsystem

A-bisInterface

AirInterface

MS

INDC Juin 2000 43


2 BASE STATION SYSTEM (BSS)

FUNCTIONS

� Relay between the NSS and mobile stations

� Cells varying from 350 m to 35 km in size

� BTSs colocated or remote from the BSC

� Location areas consisting of sets of cells

� Manages physical and logical channels

� Manages interfaces with the NSS and the operation and maintenance centre (OMC-R)

INDC Juin 2000 44


2 (continued) BASE STATION SYSTEM (BSS)

ADAPTATION TO TRAFFIC

BTS

350 m

BSC

BTS

70 km

35 km

Light trafficarea

Heavy trafficarea

NSS

BTS

INDC Juin 2000 45


2 (continued) BASE STATION SYSTEM (BSS)

BASE STATION CONTROLLER (BSC)

� Role of the BSC :

• Manages radio resources,

• Supervises BTSs (Operation and maintenance),

• Decides on and executes Handovers,

• Manages SS7 applications (BSSAP),

• Concentrates traffic to the NSS.

INDC Juin 2000 46


2 (continued) BASE STATION SYSTEM

BASE TRANSCEIVER STATION (BTS)

� Role of the BTS

• Manages radio transmission (TDMA multiplexing, frequency hopping, ciphering),

• Manages the data link layer for communication with mobile stations and the BSC,

• Handles operation and maintenance of these equipments in conjunction with the BSC,

• Provides transmission and multiplexing facilities at the Abis interface.

INDC Juin 2000 47


3 NETWORK AND SWITCHING SUBSYSTEM

CONCEPT OF INTELLIGENT NETWORKS

The introduction of new services and access to the GSM service via the Alcatel 1000 E10 are both based on the concept of Intelligent Network (IN). This is because of the independence between:

� Conventional call processing handled by the exchange

� Mobile radio functions handled by a dedicated server.

Dialogue between these two is managed by an IN interface.

INDC Juin 2000 48


3 (continued) NETWORK AND SWITCHING SUBSYSTEM (NSS)

NETWORK AND SWITCHING SUBSYSTEM

� The service switching point (SSP) is based on the Alcatel 1000 E10

� Mobile radio functions are implemented in IN servers:

• the "Radio Control Point" (RCP), integrated into the MSC handles mobility functions

• The HLR and AUC databases store subscriber characteristics and confidential data.

INDC Juin 2000 49



SSP Alcatel 1000 E10

GSM Server

� New block for mobile radio functions in the MSC

� SSP / Server interface based on SS7 protocol

Switching

Control

Op. / Maint.

GSM

Function

SS7

MSC

Matrix

INDC Juin 2000 50



A

BTS

BTS

BTS

BTS

BTS BSC

Alcatel1000 E10

SSP

IN

RCF/VLR

RCP

PSTN/SS7

HLR/AUC

MSCInterface

Air

INDC Juin 2000 51



BSC

BTS

"A" interface

Mobile subscriber units

Y

MS

SSP

Callprocessing

TUP/ISUP

NetworkSS7

PSTN

VLR RCP

interfaceMAP

HLR

AUC

NSSBSS

"IN"

Radiocontrol

functions

INDC Juin 2000 52



� Advantages of this architecture :

• Separation between applications

- switching functions handled by the SSP,

- radio control functions handled by GSM servers.

• Functions can be developed independently.

INDC Juin 2000 53

SOLUTION Alcatel 900/1800


� RCP and SSP are the two functional blocks of the MSC

� The Alcatel 1000 E10 handles all mobile radio network access functions

� The RCP handles all mobile radio functions

• mobility management and radio frequencies

• incorporates the VLR function (Visitor Location Register)

INDC Juin 2000 54



Alcatel 1000 E10 GSM 900/1800 ACCESS

Alcatel1000 E10

SS7

PSTN/

MSC

GSM 900BSS

GSM 1800BSS

SSP

GSM GSM1800

RCP

ISDN

900

INDC Juin 2000 55


3 (continued) NETWORK AND SWITCHING SUBSYSTEM

RCP RADIO CONTROL POINT (Alcatel 1421)

� Server handling GSM 900/1800 functionsSecurityRoamingHand-over

� Connected to the Alcatel 1000 E10 via the IN interface

� Modularity : n RCPs in the same Alcatel 1000 E10

� Based on the Alcatel 8360 : duplex architecture, real time application, ...

� Incorporates the VLR function

INDC Juin 2000 56



HLR HOME LOCATION REGISTER (Alcatel 1422)

� Dialogue with the MSC via the SS7 network and MAP protocol

� Based on the Alcatel 8360 : duplex architecture, real time application

� Incorporates the AUC function

INDC Juin 2000 57



� HLR : Home location register

• Stores subscriber rights (or entitlements)

• The subscriber location is always known

• Converts MS-ISDN into IMSI numbers

• Redirects terminating calls to the visited MSC

(or ISDN number if call transfer has been activated)

� Incorporates the AUC function

• Handles security functions (IMSI, Ki key and algorithms)

• Provides authentication triplets and ciphering for the VLR

INDC Juin 2000 58


4 FUNCTIONS PROVIDED

� Security

• Authentication : for each call and on each location update

• Ciphering : for each call and during location updating

• IMEI check on each call

� Roaming restricted to

• One area in the PLMN (list of cells)

• Entire PLMN

• PLMN + list of PLMNs

• All PLMNs

� Handover

• Intra-BSC

• Inter-BSC

• Inter-MSC

INDC Juin 2000 59


4 (continued) FUNCTIONS PROVIDED

DISTRIBUTION OF GSM FUNCTIONS BETWEEN NETWORK ELEMENTS

Function SSP RCP/VLR HLR/AUC

Authentication X X X

Paging X X

Registration X X X

Handover :

- checking

- connection

X

X X

Call processing :

- switching

- charging

X

X

INDC Juin 2000 60


4 (continued) BSS-NSS PROTOCOLS

SSP/RTC TUP/ISUP (Telephone/ISDN User Parts)Network Signalling

RCP/SSP IN PROCEDURESNetwork Actions

RCP/BSS BSSMAP (Base Station Management Application)

Resource Management---

channel assignmentpaginghandover

RCP/MS DTAP (Direct Transfer Application Part)

Call processing--

set-up, alertauthentication

--

connection, disconnectionlocation, registration

RCP/RCP MAP (Mobile Application Part)RCP/RCPRCP/HLR

RCP/HLR --

handoverroaming

- authentication

SSP

Mobileradio

functions

INDC Juin 2000 61


4 (continued) BSS-NSS PROTOCOLS

MSC(others)

IN

Procedures

MSC/VLR

TUP/ISUP PSTN/

ISDN

HLRMAP

MAP

SSPBSSMS

BSSMAPDTAP

"A" Interface

SSP : Service Switching PointRCP : Radio Control PointVLR : Visitor Location RegisterHLR : Home Location RegisterMS : Mobile StationBSS : Base Station SubsystemMSC : Mobile-Service Switching CentreMAP : Mobile Application Part

BSSMAP: BSS Mobile Application Part

Channel and data

air interface

PCM

RCP

VLR

DTAP : Direct Transfer Application Part

INDC Juin 2000 62


5 OPERATION AND MAINTENANCE

OPERATION AND MAINTENANCE CENTRE (OMC)

Administers and manages the mobile radio network :

- OMC-NSS for the NSS part (SSP, RCP, HLR), based on Alcatel 8360 architecture,

- OMC-R for the BSS part (BSC, BTS, transmission equipment), based on a SUN server.

�OMC - NSS

RCPSSP

HLRE10OCB283

NSS

X.25 linkto billingcentre

Magnetic tape

BSC BTS

BSS

OMC - R �

INDC Juin 2000 63

Alcatel GSM 900/1800 SOLUTION 6 VALUE-ADDED SERVICES

� Voice messaging service (VM)

� Short message service (SM-SC)

� Equipment identity register (EIR)

� Sales administration centre

• Billing

• SIM card management

• Subscriber administration

INDC Juin 2000 64


6 (continued) VALUE-ADDED SERVICES

MSCInterface

"A"Interface

"Air"

SSP

Callprocessing

RCP

RCF

VLR

TUP/ISUP

MAP

HLR/AUC

EIR

SMS-C

Voice

PSTN/ISDN

Sales Administration Centre

SS7

MailboxBSS

TUP/ISUP

INDC Juin 2000 65



MESSAGE NOTIFICATION SCENARIO

1. When the mobile subscriber cannot be reached (no answer, busy), the call can be routed to the voice messaging server (VM) on which the caller can record a message for the called subscriber.

2. The VM notifies the SM-SC of the recorded message.

3. The SM-SC sends a short message to the mobile station notifying the subscriber, even if busy on a call.

4. The SM-SC cannot notify the mobile station if it is not in idle mode or is located outside the PLMN. In this case, the SM-SC sends an MAP message to the HLR asking it to send a notification when the mobile station can be reached.

5. When the mobile station is once again reachable, the HLR alerts the SM-SC which sends the message again to the mobile station.

INDC Juin 2000 66



SHORT MESSAGE SERVICE (SMS)

� A method of interchanging alphanumeric messages (of up to 140 characters) with mobile stations

� Two types of service

• SMS-MT/PP (Short Message Service Mobile Terminated point-to-point)

• SMS-MO/PP (Short Message Service Mobile Originated point-to-point)

� SM-SC (Short Message Service Centre) saves and sends short messages

� SM-SC dialogues with the MSC and the HLR using SS7 and MAP protocol

INDC Juin 2000 67



SSP

RCP

MSC

BSCBTS

PSTN/ISDN

Voice MailboxTUP/ISUP

TUP/ISUP

X.25

SMSC

MAP

SS7 MAPHLRMAP

INDC Juin 2000 68



EIR EQUIPMENT IDENTITY REGISTER

� The EIR can bar access to the GSM network for unauthorized terminals

• Stolen terminals

• Terminals with technical problems or unapproved terminals

� The EIR is the terminal database

• Each terminal is assigned an IMEI (International Mobile Equipment Identity)

• Each IMEI is associated with a list:

� white list = authorized terminal

� grey list = suspect terminal

� black list = unauthorized terminal

� The EIR dialogues with the MSC using SS7 and MAP protocol

INDC Juin 2000 69



MSCBSCBTS

SS7Network

IMEI checkGrey list

Black list

White list

EIRTerminal

IMEI

1. At the start of the conversation, the MSC asks the terminal to send its IMEI

2. Using MAP protocol, the MSC asks the EIR to check the IMEI

3. The EIR sends a response to the MSC

4. White list � the conversation continues Grey list � the conversation continues and additional investigations are undertaken Black list � the conversation is suspended

INDC Juin 2000 70


7 INTELLIGENT NETWORK SERVICES

INTELLIGENT NETWORK SERVICES FOR THE GSM/DCS

Originating Call Screening (OCS)

Lets a subscriber to the service screen originating calls based on various criteria (date, time).

Terminating Call Screening (TCS)

Lets a subscriber to the service screen terminating calls based on various criteria (date, time, entry of a confidential code).

Mobile Universal Access Number (MUAN)

Used to route a call based on various criteria such as the date, time and location of the mobile subscriber when the special numbers are dialled.

Prepaid SIM Card (PPS)

A user can access one operator network without any subscription. A credit and a validity date is associated to the SIM card. At t(he end of each call, the credit is updated. This credit can be reload by the user.

INDC Juin 2000 71


7 (continued) INTELLIGENT NETWORK SERVICES

IN SERVICES GENERAL ARCHITECTURE

PSTN/ISDNAlcatel 1000 E10

SSP

RCP

RCPMSC

INAP

HLR

OSNM

SCP

SMP�

OSWSServer for IN services

IN services management

Service provider

Service subscriber

SSP : Service Switching PointINAP : Intelligent Network Application PartRCP : Radio Control Point

MSC : Mobile Switching CentreSCP : Service Control PointSMP : Service Management PointOSNM : Operation System for

OSWS : Operation System WorkStationNetwork Management

HLR : Home Location Register

INAP

INDC Juin 2000 72



IN SERVICES "NETWORK CONNECTION" ARCHITECTURE

PSTN/ISDNAlcatel 1000 E10

SSP

RCP

RCPMSC

INAP (IN-ER1)

HLR

OSNM

SCP

SMP�

OSWSServer for IN services

IN services management

Service provider

Service subscriber

INAP- IN-ER1- CS1

TCP/IP

INDC Juin 2000 73



IN SERVICES CAMEL PHASE 1 ARCHITECTURE

MAP : MOBILE APPLICATION PART CAP : CAMEL APPLICATION PART

GMSC HLR

SCP

MSC VLR

MAP V3Net Sig

Net Sig MAP V3

CAP V1

CAP V1 MAP V3

INDC Juin 2000 74



IN SERVICES CAMEL PHASE 2 ARCHITECTURE

SRP: SPECIALISED RESSOURCE POINT

GMSC HLR

SCP

MSC VLR

MAP V3Net Sig

CAP V2MAP V3

CAP V2

CAP V2 MAP V3

SRPNet Sig

MAP V3

Net Sig

Net Sig

INDC Juin 2000 75



IN SERVICES CAMEL PHASE 2 ALCATEL ARCHITECTURE

HLR

SCP

MAP V3ISUP

CAP V2

MAP V3

CAP V2

CAP V2 MAP V3

SRP

ISUP

MAP V3

ISUP

ISUP

SSP

RCP

SSP

RCP

INAP

INAP

gsm

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