GSM Signaling System-48

7/27/2019 GSM Signaling System-48

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GSM Signaling System


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Objectives

At the end of this course, you will be able to: Know GSM system signaling model

State various types of GSM protocol messages

Understand GSM system basic signaling procedure


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Content

GSM System Signaling Model

GSM protocol message

Basic Signaling Procedure


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GSM Interface

SGSN

AbisUm

BTS

BSC

TRAU

GGSN

MSC/VLR/GMSC

NSMU FSMU

Ater A

OMC

Qx

HLR/AUC

EIR SMC

PSTN / PLMN /

PSPDN / ISDN

BTS

BTS

BTS

Gb


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GSM system signaling model adopts the lowest threelayer of OSI seven layer protocol model, from low to

high:

Application layer

Link layer/Network layer

Physical layer


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Physical Layer

The physical layer provides error protectiontransmission. It defines the electric parameters of

transmission.

In ZTE-GSM digital mobile communication

systems, The physical layer of Um interfacebetween MS and BTS is Radio link. Abis interface

physical layer adopts 75-ohm coaxial cable or

120-ohm symmetrical twisted pair whose rate is

2Mbit/s.


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Data Link Layer

The data link layer major functions: frametransmissionerror-free transmission and realize

end-to-end bits transfer between two connective

entities. Open maintenance and close the

connection of two connective entities. The link layer protocol used by the GSM system at

the radio interface is the LAPDm protocol (Dm

channel link access procedure). The data link

layer of Abis interface between BTS and BSC is

LAPD (D channel link access procedure).


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Application Layer

Application Layer

CM MM RR

CC SS SMS


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Application Layer

Radio Resources (RR) management handles theestablishment, maintenance and release of physical

channels. Its major functions are performed by BSC. Part

of functions are performed by BTS.

Mobility Management (MM) deals with the mobile stations

register and the identify of the mobile subscriber, The

function are performed by MSC.

The CM Layer is composed of three functional entities:

Call Control (CC), deals with the functions to establish

maintenance and release the callShort Message Service

support (SMS) and Supplementary Service support (SS).


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Mobile

Switching

Centre

(MSC)

) ) )Base

Transceiver

Station

(BTS)

Base

Station

Controller

(BSC)

Equipment

ID

Register

(EIR)

Visitor

Location

Register

(VLR)

Home

Location

Register

(HLR)

Authenti-

cation

Centre

(AUC)

Mobile

Switching

Centre

(MSC)

Public Switched

Telephone Network

(PSTN)

MAP/TCAP + ISUP/TUP

To other VLR

ISUP/TUP

DTAP + BSSMAP

MAP/TCAP

MAP/TCAP MAP/TCAP

BTSM

A-bis interfaceA interface

GSM protocol


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DTAP

DTAP Direct Transfer Application PartBSSMAP BSS Management Application PartCM Call ManagementMM Mobile ManagementRR Radio Resource Management

SCCP Signalling Connection Control PartMAP Mobile Application PartTCAP Transaction Capability Application PartISUP ISDN User PartMTP Message Transfer Part

CM

MM

RR

Sig. layer 2

Layer 1 (air)

Sig. layer 2

Sig. layer 1

MTP

SCCP

BSSMAPRR

(CM+MM)

MS BSC

MTP MTP

SCCP SCCP

CM

MM

BSSMAP TCAP

MAP

I

S

U

P

MSC

Sig. layer 2

Layer 1 (air)

BTS

(CM)

(MM)

(RR)

(CM)

(MM)

(RR)

(CM)

(MM)

(LAPDm) (LAPDm) (LAPD)Sig. layer 2

Sig. layer 1

(LAPD)

BTSMBTSMRR'

BTSM BTS Management

Um Interface Abis Interface A Interface Inter-MSC

Interface

GSM Protocol Architecture


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Content


GSM protoco l message



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Um interface protocol stack

CM

MM

RR

LAPDm

Layer1 Layer1

LAPDm

RR

MSBTS

Um interface


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LAPDm frame format

The address field contains the service

access point identifier (SAPI).

SAPI = 0 represents the signaling link

SAPI = 3 represents the short message link

In the control field, N (S) represents the sending serial number

N (R) represents the receiving serial number

Address Control Information

SAPI N(S) N(R)


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Operation mode

Acknowledged mode: Requires the confirmationfrom the receiver. This mode provides a whole set

of control mechanism for error recovering and flow

control, the establishment mechanism and release

mechanism for multi-frame operations. Unacknowledged mode: The receiver is not

required to send a confirmation upon reception of

a UI frame. This operation mode does not provide

flow control or error recovering mechanism.


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RR messages

Type Message

Channel establishment message Immediate assignment

Immediate assignment reject

Ciphering message Ciphering mode command

Ciphering mode complete

Handover message

Handover command

Handover complete

Handover failure

Handover access

Channel release message Channel releasePaging message Paging request

Paging response

System info System info:18


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MM messages

Type Message

Registration messages

IMSI detach indication

Location updating accept

Location updating reject

Location updating request

Security messages

Authentication reject

Authentication request

Authentication response

Identity request

Identity response

TMSI reallocation commandTMSI reallocation complete

Connection-management messages

CM service accept

CM service reject

CM service request


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CC messages

Type Message

Call establishment messages

Alerting

Call confirmed

Call proceeding

Connect

Call clearing messages

Disconnect

Release

Release complete

Miscellaneous messages

Congestion control notify

Start DTMF

Stop DTMF


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Abis Interface Protocol stack

Abis

BTS

BTSM

LAPD

Layer1

BSC

interface

Layer1

LAPD

BTSM

RR


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LAPD Protocol

SAPI = 0 represents the signaling link,

SAPI = 62 represents the O&M link, and

SAPI = 63 represents the management link of the LapD layer.

flag Address Control Information FCS flag

SAPI TEI N(S) N(R)

1 0-260 2 1


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A interface protocol stack

BSC

MTP3

MTP2

Layer1

MSC

A interface

Layer1

MTP2

MTP3

RR

SCCP SCCP

BSSAP BSSAP

MM

CM


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Relationship between SCCP and OSI model

MTP-1

MTP-2

MTP-3

SCCP

ISP

TCAP

INAP OMAP MAP BSSAP ISUP TUP

HLR VLR

Layer1

Layer2

Layer3

46

Layer 7


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BSSAP

MTP

SCCP

Distribution

BSSMAP DTAP

BSSAP

RR

MM

CC

MTP

SCCP

Distribution

BSSMAP DTAP

BSSAP

L1

LAPDm

RR

CC

MM

RR

LAPDm

L1

MSCBSS

MS

DTAP

BSSMAP DTAP


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SCCP message

CR Connection request CC Connection confirm

CREF Connection refused

RLSD Released RLC Release complete

DT1 Data form 1

UDT Unit data

UDTS Unit data service


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BSSMAP Message -1

Assignment messages (setup of traffic channels) Assignment request Assignment complete

Assignment failure

Handover messages Handover request (to BSC: request for handover to that BSC)

Handover required (to MSC: inter BSC/MSC handover required)

Handover request ack. (to MSC: acknowledge of handover request) Handover command (to BSC: contains new radio channel/BTS for the

MS)

Handover complete (to MSC: commanded handover successful)

Handover failure (to MSC: commanded handover unsuccessful)

Handover performed (to MSC: BSC has performed internal handover)

Handover candidate enquiry (to BSC: MSC requests list of MS that could be

handed over to another cell)

Handover candidate response (to MSC: answer to handover candidate enquiry)

Handover required reject (to BSC: required handover unsuccessful)

Handover detect (to MSC: commanded handover successful)


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BSSMAP Message -2

Release messages Clear command (release of traffic channel) Clear complete

Clear request

SAPI n clear command (control of layer 2 SAPI n on the radio interface)

SAPI n clear complete

SAPI n reject

General messages Reset (initialisation of BSS or MSC due to failure)

Reset acknowledge

Overload (processor or CCCH overload)

Trace invocation (start production of trace record

Reset circuit (initialisation of single circuit due to failure)

Terrestrial resource messages Block (management of circuits/time slots between MSC and

BTS)

Blocking acknowledge

Unblock

Unblocking acknowledge


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BSSMAP Message -2

Radio resource messages Resource request (available radio channels in

BSS cells)

Resource indication

Paging (paging of MS) Cipher mode command (start encryption)

Classmark update (change of MS power class)

Cipher mode complete

Queuing indication (indicates delay in

assignment of tch)


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Content

GSM System Signaling Model GSM protocol message



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Mobile Originating Call Establishment Procedure -1

MS BTS BSC MSCCH REQ(1)

CH RQD(2)

CH ACT(3)

IMM ASS(6)

CH ACT ACK(4)

IMM ASS CMD(5)

SABM(7)

UA(10)EST IND(8)

CM SERV REQ(9)

AUTH REQ(11)

AUTH REQ(12)

AUTH RSP(13)AUTH RSP(14)

CIPH MODE CMD(16)

CIPH MODE CMP(18)CIPH MODE CMP(19)

CIPH MODE CMD(17)

CIPH MODE CMD(15)


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MS BTS BSC MSC

TMSI REALL CMD(20)TMSI REALL CMD(21)

TMSI REALL CMP(22)TMSI REALL CMP(23)

SETUP(24)SETUP(25)

CALL PRO(26)CALL PROCEEDING(27)

ASSIGN REQ(28)CH ACT(29)

CH ACT ACK(30)

ASSIGNMENT COMMAND(31)

SABM(32)

UA(34)EST IND(33)

ASSIGNMENT COMPLETE(35)ASSIGN CMP(36)

RF CH REL(37)

RF CH REL ACK(38)


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MS BTS BSC MSC

ALERTING(39)ALERTING(40)

DEACT SACCH(55)

CONNECT ACK(43)CONNECT ACK(44)

RELEASE(49)

CONNECT(41)CONNECT(42)

MEAS REPORT(45)MEAS REPORT(46)

DISCONNECT(47)

DISCONNECT(48)

RELEASE(50)

RELEASE COMPLETE(51)RELEASE CMP(52)

CLEAR CMD(53)CHANNEL RELEASE(54)

DISC(56)

UA(57)REL IND(58)

RF CH REL(59)

RF CH REL ACK(60)CLEAR CMP(61)

SCCP REL(62)

SCCP REL ACK(63)


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Mobile Terminating Call Establishment Procedure -1

MS BTS BSC MSC

CH REQ(4)CH RQD(5)

CH ACT(6)

IMM ASS(9)

CH ACT ACK(7)

IMM ASS CMD(8)

SABM(10)

UA(13)EST IND(11)

PAGE RSP(12)

AUTH REQ(14)

AUTH REQ(15)


CIPH MODE CMD(19)


CIPH MODE CMD(20)

CIPH MODE CMD(18)

PAGING CMD(1)PAGING CMD(2)PAGING RQT(3)


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MS BTS BSC MSC

TMSI REALL CMD(23)TMSI REALL CMD(24)


ASSIGN REQ(31)CH ACT(32)

CH ACT ACK(33)


SABM(35)

UA(37) EST IND(36)

ASSIGNMENT COMPLETE(38)ASSIGN CMP(39)

RF CH REL(40)

RF CH REL ACK(41)

SETUP(27)SETUP(28)

CALL CONFIRMED(29)

CALL CONF(30)


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MS BTS BSC MSC

DEACT SACCH(58)

RELEASE(52)


DISCONNECT(50)DISCONNECT(51)

RELEASE(53)

RELEASE COMPLETE(54)RELEASE CMP(55)


DISC(59)

UA(60)REL IND(61)

RF CH REL(62)


SCCP REL(65)

SCCP REL ACK(66)

ALERTING(42)ALERTING(43)

CONNECT(44)CONNECT(45)

CONNECT ACK(46)CONNECT ACK(47)


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Location Update Procedure -1

MS BTS BSC MSC

CH REQ(1) CH RQD(2)

CH ACT(3)

IMM ASS(6)

CH ACT ACK(4)

IMM ASS CMD(5)

SABM(7)

UA(10) EST IND(8) LOC UPDATE REQ(9)

AUTH REQ(15)AUTH REQ(16)


IDENTITY REQ(11)IDENTITY REQ(12)

IDENTITY RSP(13)IDENTITY RSP(14)

CIPH MODE CMD(20)


CIPH MODE CMD(21)

CIPH MODE CMD(19)


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Location Update Procedure -2

MS BTS BSC MSC

LOC UPDATE ACC(24)LOC UPDATE ACCEPT(25)


DEACT SACCH(30)

CLEAR CMD(28)

CHANNEL RELEASE(29)

DISC(31)

UA(32)REL IND(33)

RF CH REL(34)

RF CH REL ACK(35)

CLEAR CMP(36)SCCP REL(37)

SCCP REL ACK(38)


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Intra Cell Handover Procedure

MS BTS BSC MSC

MEASURE REPORT(1)MEASURE REPORT(2)

CH ACT(3)

CH ACT ACK(4)

SABM(6)

UA(8)EST IND(7)

RECEIVE READY(10)


ASSIGNMENT COMPLETE(9)

HO PERFORMED(11)

RF CH REL ACK(13)

RF CH REL(12)


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Intra BSC Handover Procedure

MS BTS1 BSC MSCMEAS REPORT(1)

MEAS REPORT(2)

CH ACT ACK(4)

CH ACT(3)

PHYSICAL INFO(9)

HO ACCESS(7)

HO PERFORMED(16)

HO CMP(15

BTS2

HO CMD(5)HO CMD(6)

HO DETECT(8)

SABM(10)

EST IND(11)

UA(12)

HO CMP(13)

RECEIVERREADY(14)

RF CH REL ACK(18)

RF CH REL(17)


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Inter BSC Handover ProcedureMS BTS1 BSC1 BSC2


CH ACT(5)

CH ACT ACK(6)

HO CMD(8)

HO REQUIRED(3)

BTS2

HO REQ(4)

HO CMD(9)

HO ACCESS(10)

MSC

HO REQ ACK(7)

HO DETECT(11)

HO DETECT(12)

PHYSICAL INFO(13)

SABM(14)

EST IND(15)

UA(16)

HO CMP(17)

RECEIVER READY(18)

HO CMP(19)

HO CMP(20)

CLEAR COMMAND(21)

RF CH REL(22)

RF CH REL ACK(23)

CLEAR COMPLETE(24)


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Call Re-establishment Procedure

MS BTS BSC MSC

CONN FAIL IND(1)

CLEAR CMD(3)

CLEAR REQ(2)

CHANNEL REQ(5)

CM RE-EST REQ(6)

CIPH MODE CMD(7)CIPH MODE CMP(8)

STATUS(12)

STATUS ENQUIRY(11)

CLEAR CMP(4)

ASS REQ(9)

ASS CMP(10)


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Directed Retry Procedure

MS BTS1 BSC MSC BTS2 MSCH REQ(1)

CH RQD(2)

CH ACT(3)

CH ACT ACK(4)

IMM ASS CMD(5)

SABM(6)

UA(7)EST IND(8)

CR(9)

CC(10)

CM SERVICE ACCEPTED(11)

SETUP(12)

CALL PROCEEDING(13)

ASS REQ(14)

CHANNEL ACT(15)

CHANNEL ACT ACK(16)HANDOVER COMMAND(17) HO ACCESS(18)

HO DETECT(19)PHY INFO(20)

SABM(21)

UA(23)EST IND(22)

HO CMP(24)

ASS CMP(25)

S O S CC S


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Short Message Procedure On SDCCH When MS Is

Calling -1

MS BTS BSCMSC

CH REQ(1)CH RQD(2)

CH ACT(3)

CH ACT ACK(4)

IMM ASS CMD(5)

SABM(6)UA(7)

EST IND(8)CM SERV REQ(9)

AUTH REQ(11)

AUTH RSP(12)

CC(10)

SABM(SAPI3)(13)

UA(14)EST IND(SAPI3)(15)

CIPH MODE CMD(16)

CIPH MODE CMP(17)

CP DATA(18)

CP ACK(19)

Sh t M P d O SDCCH Wh MS I


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Calling -2

MS BTS BSC MSC

CP DATA(20)

CP ACK(21)

DEACT SACCH(24)


DISC(25)

UA(26)REL IND(27)

RF CH REL(28)


SCCP REL(31)

SCCP REL ACK(32)



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Called -1

MS BTS BSC MSC

CH REQ(3)CH RQD(4)

CH ACT(5)

CH ACT ACK(6)

IMM ASS CMD(7)

SABM(8)

UA(10)EST IND(9)

CM SERV REQ(11)

AUTH REQ(13)

AUTH RSP(14)

CC(12)

CIPH MODE CMD(15)

CIPH MODE CMP(16)

PAGING CMD(1)PAGING CMD(2)

CP DATA(17)EST REQ(SAPI3)(18)

SABM(19)

UA(20)EST CMP(SAPI3)(21)



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Called -2

CP DATA(22)

CP ACK(23)

DEACT SACCH(28)


DISC(29)

UA(31)REL IND(30)

RF CH REL(32)RF CH REL ACK(33)

CLEAR CMP(34)

SCCP REL(35)

SCCP REL ACK(36)

CP DATA(24)

CP ACK(25)

MS BTS BSC MSC

Short Message Procedure On SACCH When


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MS Is Calling

MS BTS BSC MSC

CM SERVICE REQ1

CM SERVICE ACC(2)

SABM(SAPI3)(3)

UA(4)EST IND(SAPI3)(5)

CP DATA(6)

CP ACK(7)

CP DATA(8)

CP ACK(9)

ACTIVE CALL

ACTIVE CALL



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MS Is Called

MS BTS BSC MSC

SABM(3)

UA(4)EST CNF(SAPI3)(5)

CP DATA(8)

CP ACK(9)

CP DATA(6)

CP ACK(7)

ACTIVE CALL

ACTIVE CALL

CP DATA(1)EST REQ(SAPI3)(2)


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GSM Signaling System-48

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