Download - 03 GO_SP2001_E01_1 GSM Signaling System-48
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GSM Signaling System
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ObjectivesAt the end of this course, you will be able to:Know GSM system signaling model State various types of GSM protocol messagesUnderstand GSM system basic signaling procedure
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ContentGSM System Signaling ModelGSM protocol message Basic Signaling Procedure
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GSM Interface
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GSM System Signaling ModelGSM system signaling model adopts the lowest three layer of OSI seven layer protocol model, from low to high:
Application layerLink layer/Network layerPhysical layer
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Physical LayerThe physical layer provides error protection transmission. It defines the electric parameters of transmission. In ZTE-GSM digital mobile communication systems, The physical layer of Um interface between 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 LayerThe data link layer major functions: frame transmissionerror-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
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Application LayerRadio Resources (RR) management handles the establishment, 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 establishmaintenance and release the callShort Message Service support (SMS) and Supplementary Service support (SS).
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GSM protocolPublic SwitchedTelephone Network(PSTN)MAP/TCAP + ISUP/TUPTo other VLRISUP/TUPDTAP + BSSMAPMAP/TCAPMAP/TCAPMAP/TCAPBTSMA-bis interfaceA interface
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GSM Protocol ArchitectureDTAPDTAP Direct Transfer Application PartBSSMAP BSS Management Application PartCM Call ManagementMM Mobile ManagementRR Radio Resource ManagementSCCP Signalling Connection Control PartMAP Mobile Application PartTCAP Transaction Capability Application PartISUP ISDN User PartMTP Message Transfer PartCMMMRRSig. layer 2Layer 1 (air)Sig. layer 2Sig. layer 1MTPSCCPBSSMAPRR(CM+MM)MSBSCMTPMTPSCCPSCCPCMMMBSSMAPTCAPMAPISUPMSCSig. layer 2Layer 1 (air)BTS(CM)(MM)(RR)(CM)(MM)(RR)(CM)(MM)(LAPDm)(LAPDm)(LAPD)Sig. layer 2Sig. layer 1(LAPD)BTSMBTSMRR'BTSM BTS ManagementUm InterfaceAbis InterfaceA InterfaceInter-MSCInterface
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ContentGSM System Signaling ModelGSM protocol message Basic Signaling Procedure
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Um interface protocol stack
CM
MM
RR
LAPDm
Layer1
Layer1
LAPDm
RR
MS
BTS
Um interface
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LAPDm frame formatThe address field contains the service access point identifier (SAPI). SAPI = 0 represents the signaling linkSAPI = 3 represents the short message linkIn 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 modeAcknowledged mode: Requires the confirmation from 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
TypeMessageChannel establishment messageImmediate assignmentImmediate assignment rejectCiphering messageCiphering mode commandCiphering mode complete
Handover messageHandover commandHandover completeHandover failureHandover accessChannel release messageChannel releasePaging messagePaging request Paging responseSystem infoSystem info:18
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MM messages
TypeMessageRegistration messagesIMSI detach indicationLocation updating acceptLocation updating rejectLocation updating request
Security messagesAuthentication rejectAuthentication requestAuthentication responseIdentity requestIdentity responseTMSI reallocation commandTMSI reallocation completeConnection-management messagesCM service acceptCM service rejectCM service request
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CC messages
TypeMessage
Call establishment messages
AlertingCall confirmedCall proceedingConnect
Call clearing messagesDisconnectReleaseRelease completeMiscellaneous messagesCongestion control notifyStart DTMFStop 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 ProtocolSAPI = 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
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Relationship between SCCP and OSI model
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BSSAP
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SCCP messageCRConnection requestCCConnection confirmCREFConnection refusedRLSDReleasedRLCRelease completeDT1Data form 1UDTUnit dataUDTSUnit data service
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BSSMAP Message -1Assignment messages (setup of traffic channels)Assignment requestAssignment completeAssignment failureHandover 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 handedover 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 -2Release messagesClear command (release of traffic channel)Clear completeClear requestSAPI n clear command (control of layer 2 SAPI n on the radio interface)SAPI n clear completeSAPI n reject
General messagesReset(initialisation of BSS or MSC due to failure)Reset acknowledgeOverload(processor or CCCH overload)Trace invocation(start production of trace recordReset circuit(initialisation of single circuit due to failure)Terrestrial resource messagesBlock (management of circuits/time slots between MSC and BTS)Blocking acknowledgeUnblockUnblocking acknowledge
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BSSMAP Message -2Radio resource messagesResource request(available radio channels in BSS cells)Resource indicationPaging(paging of MS)Cipher mode command(start encryption)Classmark update(change of MS power class)Cipher mode completeQueuing indication(indicates delay in assignment of tch)
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ContentGSM System Signaling ModelGSM protocol message Basic Signaling Procedure
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Mobile Originating Call Establishment 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)
CM SERV REQ(9)
AUTH REQ(11)
AUTH REQ(12)
AUTH RSP(13)
AUTH RSP(14)
CIPH MODE CMD(15)
CIPH MODE CMD(16)
CIPH MODE CMP(18)
CIPH MODE CMP(19)
CIPH MODE CMD(17)
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Mobile Originating Call Establishment Procedure -2
MS
BTS
BSC
MSC
SETUP(24)
SETUP(25)
CALL PRO(26)
CALL PROCEEDING(27)
ASSIGN REQ(28)
ASSIGNMENT COMMAND(31)
CH ACT(29)
CH ACT ACK(30)
SABM(32)
UA(34)
TMSI REALL CMD(20)
TMSI REALL CMD(21)
TMSI REALL CMP(22)
TMSI REALL CMP(23)
EST IND(33)
ASSIGNMENT COMPLETE(35)
ASSIGN CMP(36)
RF CH REL(37)
RF CH REL ACK(38)
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Mobile Originating Call Establishment Procedure -3
MS
BTS
BSC
MSC
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)
ALERTING(39)
ALERTING(40)
CHANNEL RELEASE(54)
DISC(56)
DEACT SACCH(55)
CONNECT ACK(43)
CONNECT ACK(44)
UA(57)
RELEASE(49)
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)
AUTH RSP(16)
AUTH RSP(17)
CIPH MODE CMD(19)
CIPH MODE CMP(21)
CIPH MODE CMP(22)
CIPH MODE CMD(20)
CIPH MODE CMD(18)
PAGING CMD(1)
PAGING CMD(2)
PAGING RQT(3)
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Mobile Terminating Call Establishment Procedure -2
MS
BTS
BSC
MSC
TMSI REALL CMD(23)
TMSI REALL CMD(24)
TMSI REALL CMP(25)
TMSI REALL CMP(26)
SETUP(27)
SETUP(28)
CALL CONFIRMED(29)
CALL CONF(30)
ASSIGN REQ(31)
CH ACT(32)
CH ACT ACK(33)
ASSIGNMENT COMMAND(34)
SABM(35)
UA(37)
EST IND(36)
ASSIGNMENT COMPLETE(38)
ASSIGN CMP(39)
RF CH REL(40)
RF CH REL ACK(41)
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Mobile Terminating Call Establishment Procedure -3
MS
BTS
BSC
MSC
ALERTING(42)
ALERTING(43)
DEACT SACCH(58)
CONNECT(44)
CONNECT(45)
RELEASE(52)
CONNECT ACK(46)
CONNECT ACK(47)
MEAS REPORT(48)
MEAS REPORT(49)
DISCONNECT(50)
DISCONNECT(51)
RELEASE(53)
RELEASE COMPLETE(54)
RELEASE CMP(55)
CLEAR CMD(56)
CHANNEL RELEASE(57)
DISC(59)
UA(60)
REL IND(61)
RF CH REL(62)
RF CH REL ACK(63)
CLEAR CMP(64)
SCCP REL(65)
SCCP REL ACK(66)
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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)
AUTH RSP(17)
AUTH RSP(18)
IDENTITY REQ(12)
IDENTITY RSP(13)
IDENTITY REQ(11)
IDENTITY RSP(14)
CIPH MODE CMD(20)
CIPH MODE CMP(22)
CIPH MODE CMP(23)
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)
TMSI REALL CMP(26)
TMSI REALL CMP(27)
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 COMMAND(5)
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
MSC
MEAS REPORT(1)
MEAS REPORT(2)
CH ACT ACK(4)
CH ACT(3)
HO DETECT(8)
PHYSICAL INFO(9)
SABM(10)
RF CH REL ACK(18)
HO CMD(5)
HO ACCESS(7)
RF CH REL(17)
HO PERFORMED(16)
HO CMP(15
BTS2
HO CMD(6)
EST IND(11)
UA(12)
HO CMP(13)
RECEIVER READY(14)
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Inter BSC Handover Procedure
MS
BTS1
BSC1
BSC2
MEAS REPORT(1)
MEAS REPORT(2)
CH ACT(5)
CH ACT ACK(6)
HO CMD(8)
HO REQUIRED(3)
HO CMP(17)
RECEIVER READY(18)
BTS2
HO REQ(4)
HO CMP(19)
HO CMP(20)
CLEAR COMMAND(21)
HO CMD(9)
RF CH REL(22)
HO ACCESS(10)
RF CH REL ACK(23)
CLEAR COMPLETE(24)
MSC
HO REQ ACK(7)
HO DETECT(11)
HO DETECT(12)
PHYSICAL INFO(13)
SABM(14)
EST IND(15)
UA(16)
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Call Re-establishment Procedure
MS
BTS
BSC
MSC
CLEAR CMP(4)
CONN FAIL IND(1)
CLEAR CMD(3)
ASS REQ(9)
CLEAR REQ(2)
ASS CMP(10)
CHANNEL REQ(5)
CM RE-EST REQ(6)
CIPH MODE CMD(7)
CIPH MODE CMP(8)
STATUS(12)
STATUS ENQUIRY(11)
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Directed Retry Procedure
MS
BTS1
BSC
MSC
BTS2
MS
CH REQ(1)
CH RQD(2)
CH ACT(3)
CC(10)
CH ACT ACK(4)
IMM ASS CMD(5)
SABM(6)
UA(7)
EST IND(8)
CR(9)
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)
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Short Message Procedure On SDCCH When MS Is Calling -1
MS
BTS
BSC
MSC
CH REQ(1)
CH RQD(2)
CH ACT(3)
CC(10)
CH ACT ACK(4)
IMM ASS CMD(5)
SABM(6)
UA(7)
EST IND(8)
CM SERV REQ(9)
SABM(SAPI3)(13)
AUTH REQ(11)
AUTH RSP(12)
UA(14)
CIPH MODE CMD(16)
CIPH MODE CMP(17)
CP DATA(18)
CP ACK(19)
EST IND(SAPI3)(15)
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Short Message Procedure On SDCCH When MS Is Calling -2
MS
BTS
BSC
MSC
CP DATA(20)
CP ACK(21)
DEACT SACCH(24)
CLEAR CMD(22)
CHANNEL RELEASE(23)
DISC(25)
UA(26)
REL IND(27)
RF CH REL(28)
RF CH REL ACK(29)
CLEAR CMP(30)
SCCP REL(31)
SCCP REL ACK(32)
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Short Message Procedure On SDCCH When MS Is 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)
SABM(19)
UA(20)
PAGING CMD(1)
PAGING CMD(2)
CP DATA(17)
EST REQ(SAPI3)(18)
EST CMP(SAPI3)(21)
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Short Message Procedure On SDCCH When MS Is Called -2
CP DATA(24)
CP ACK(25)
CP DATA(22)
CP ACK(23)
DEACT SACCH(28)
CLEAR CMD(26)
CHANNEL RELEASE(27)
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)
MS
BTS
BSC
MSC
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Short Message Procedure On SACCH When 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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Short Message Procedure On SACCH When MS Is Called
MS
BTS
BSC
MSC
CP DATA(1)
EST REQ(SAPI3)(2)
SABM(3)
UA(4)
EST CNF(SAPI3)(5)
CP DATA(8)
CP ACK(9)
CP DATA(6)
CP ACK(7)
ACTIVE CALL
ACTIVE CALL