1. GSM Signaling Procedure
Huawei Vietnam RF Team

2. GSM Network Protocol DTAP RSL OML OSI : Open System Interconnection
SCCP : Signalling Connection Control Part (OSI Layer 3 complementary Software in SS7 code, used to manage signalling channel without associated speech channel)
MTP : Message Transfert Part
DTAP : Direct Transfert Application Part (BSC <-> MS transfert protocol)
MAP : Mobile Application Part (Protocol Used between NSS Machine)
TCAP : Transaction Capabilities Application Part (Layer 7 sub-set in CCITT n°7 signalling system)

3. GSM Network Protocol Layer 3 Introduction
RR :（Radio Resource Management）
Control by MS、BTS and BSC
Function Sample
Paging Management
Ciphered Mode Management
Frequency Redefinition
Dedicated Channel Assignment
Handover Management
Measures and Power Control
MM :（Mobility Management）
Control by MS and MSC / VLR
Authentication / Identification Procedures
Location Updating
IMSI Attach / Detach
Example of RR procedure message:
Immediate Assignment (seizure of a SDCCH)
Assignment Command (seizure of SD or TCH)
Handover Command
Channel Release
Paging Request
Measurement Report
Example of MM procedure message :
IMSI Detach Indication
Location Updating Request
Authentication Request
Identity Request
CM Service Request
Example of CCprocedure message :
Alerting
Connect
Progress
Setup
Disconnect
Release

4. GSM Network Protocol CC : （Call Control） Control by MS and MSC
Function Sample
Call processing and routing
Short Message Service
Supplementary Service

5. GSM Frame Structure

6. GSM Multi-Frame Channel

7. GSM Multi-Frame Channel

8. Singling Link Establish Procedure
Content
Establish Signaling Link, used for signaling transmission
When MS want to connect to network, firstly must establish the radio signaling link and A-interface link
Step included
Paging Procedure
Random Access Procedure
Immediate Assignment Procedure
SCCP Connection Establishment Procedure
RR Management : functions related to the management of the common transmission resources. Functions can establish, maintain or release RR connections. RR includes the reception of BCCH and CCH when no RR connection is established.
Paging Procedure : Network inform that a MS is called
Random Access Procedure : Method by which the MS requests Air Interface Resource from the network
Immediate Assignment Procedure : BSS allocates a resource to the MS and the MS & Network establish a radio signalling link between themseleves. This procedure is carried out automatically by the BSC without informing the MSC
SCCP : Signaling Connection Control Part
SCCP Connection Establishment Procedure : When Air interface signalling connection is succesfully established, the MSC is informed of the presence of the mobile by the use of SCCP

9. Singling Link Establish Procedure
Entity MS
BTS
RACH_TA_Filtering
BSC
MSC
Channel Request
ST3126
Channel Required
Timer；
S -- Start；
E -- End
（RACH）（Est Cause，Rnd Nbr）
（Est Cause，Rnd Nbr，FN，TA）
Channel Activation（SD）
ST9103
（TA，BS/MS_TxPwr -->Max，Chann）
Channel Act Ack （SD）
ET9103
Immediate Assignment
Command
For 2 MS at same time
ST3101
（Rnd Nbr，TDMA Frame Nbr，Chan ，TA）
（AGCH）
Channel Request : available causes : Emergency call, Call re-establishment, Answer to paging, OC and LU. Contains a Random Number to distinguish the answer of the BTS. Send on the RACH. The mobile can send several Ch Req. At the end of the sequence, T3126 is tarted
Channel Required : Common Channel Management. Transmission of the Random Number. Timing Advance Estimation
Immediate Assign CMD : send on the AGCH to the mobile in IDLE mode to change the channel configuration to a dedicated configuration while staying in the same cell
SABM (Set Asynchronous Balanced Mode: to) : create a LAPDm connection. Upon the seizure of the assigned dedicated channel, the mobile station establishes the main signalling link on this channel by sending a L2 SABM frame containing the L3 service request message (CM Serv Req, LU Req, IMSI Detach, Pagres). Send on SDCCH
UA (Unnumbered Acknoledge). The service request send by the MS is retruned by the network. The MS compares the message send in the SABM and received in the UA, and leaves the channel in case they do not match.(Send on SDCCH). This allow the discrimination of 2 mobiles
Establish Ind : idem as SABM. C01 is incremented with Paging Response. C02 with LU,OC.
SCCP Connection Required : the LAC and CI of the BTS are given
C40 : number of seconds a SDCCH channel is used
UI Imm Assignment / Imm Ass Ext
CM Serv Req，Pag Res，Loc Update Req
ET3126
Set Asynchronous Balance
SABM [L3 Info]
（SDCCH）
Est Ind [L3 Info]
ET3101
UA [L3 Info]
SCCP Con Rqrd [L3]
ST9105
Unnumbered Ack
SCCP Conn Confirm
ET9105 Um
Abis A

10. Singling Link Establish Procedure——Abis
Abis Signaling
Channel Required

11. Singling Link Establish Procedure——Abis
Channel Activation

12. Singling Link Establish Procedure——Abis
Immediately Assignment

13. Authentication, Identification, Ciphering, TMSI Re-allocation
RAND and Ki by A3 algorithm get SRES; by A8 algorithm get Kc
VLR get from HLR the RAND/SRES/Kc MS
BTS
BSC
MSC
Authentication Req
Authentication Req
（RAND）
ST3260
Authentication Req
Authentication Resp
Authentication
Authentication Resp
Check SRES
（SRES）
Authentication Resp
ET3260
*Authentication Reject*
Identification Request
Identification Request
Identification Request
ST3270
Identification
Identification Response
Identification Response
（IMSI）
Identification Resp
ET3270
（Alg（A5））
（Alg，Kc）
（Permitted Alg，Kc）
Ciphering Mode Cmd
Encryption Command
Ciphering Mode Cmd
Authentifiaction procedure (MM Procedure): To check if the identity of the mobile is acceptable or not. Provide parameters enabling MS to calculate the new ciphering key. This procedure is used at each call setup, suplementary service, location updating.
Identification procedure (MM Procedure) : Procedure used by the network to request a Mobile station to provide his IMSI
Ciphering Mode setting procedure (RR Procedure) :Used to set the ciphering mode. Indicate wether ciphering shall be used or not and if yes which algortihm to use
TMSI Realloc Proc (MM Procedure) : Provide identity confidentiality to the MS. The TMSI has significance only within a location area.
Ciphering
Ciphering Mode Cmp
Ciphering Mode Cmp
Ciphering Mode Cmp
TMSI Realloc Cmd
TMSI Realloc Cmd
（TMSI）
ST3250
TMSI Realloc Cmd
TMSI Realloc
TMSI Realloc Cmp
TMSI Realloc Cmp
TMSI Realloc Cmp
ET3250

14. Authentication, Identification, Ciphering, TMSI Re-allocation
Authentication Request

15. Authentication, Identification, Ciphering, TMSI Re-allocation
Authentication Response

16. Authentication, Identification, Ciphering, TMSI Re-allocation
Identification Response

17. TCH Assignment Procedure
Content
Normal Assignment for TCH
Special case
Queuing
Directed Retry
OACSU : Off Air Call Setup : allow the late assignment of the TCH (after the Alerting). This feature allows an increase of the efficiency of the TCH.
Queuing : allows a TCH channel allocation to be queued for a time whilst no TCH free
Directed Retry : allows the BSS to assign a TCH on another cell by internal handover

18. TCH Assignment ProcedureMS
BTS
BSC
MSC
Assignment Request
（SDCCH）
STrr1
Physical Context Request
（Chn Type，Priority，CIC，DL DTX，Queuing Flag）
ST9108
（TA，MS/BS_TxPwr）
Physical Context Confirm
ET9108
（TA，MS/BS_TxPwr）
Channel Activation TCH
ST9103
Channel Activation Ack.
ET9103
（MA，TS，HSN，MAIO，MS_TxPwr）
Assignment Command
Assignment Command
ST3107
On TCH if need signaling, then use Stealing Flag transfer TCH into FACCH
SABM (FACCH)
Establish Indication
Phys Con Req : Allow the BSC to obtain information on the phsical context of a radio channel just prior to a channel change.Includes the BS Power, MS Power, TA
Assignment Request : Detail of the resource that is required (channel rate, channel type,...). It also include the terrestrial circuit that shall be used between the BSC & MSC. If the Assignment is not completed, the Assigenemtn failure is send on A interface with cause :
RIMF : the BSS doesn't receive the Assigenemtn complete
RIF : failure on the Radio or A-bis interface during activation of the channel
No Radio Resource available
Requested Terrestrial Resource unavailable
Requested Terrestrial Resource alreqdy allocated
Radio Interface Failure, Reversion to old channel
Ciphering Algo not supported
Assignment Command : send on SDCCH -> to change the Channel configuration
SABM, ESTIN, UA : see Radio & Link Establishment
C16 : incremented when a RTCH channel has been successfully selected for any other purpose than HO.
C18 : incremented when a RTCH has been successfully seized by the MS for any other purpose than HO UA
Assignment Complete
Assignment Complete
ET3107
Assignment Cmp
ETrr1
RF Channel Release (SD)
RF Channel Release Ack.

19. TCH Assignment Procedure---A interface
Assignment Request
EFR
Queuing

20. TCH Assignment Procedure---Abis interface

21. TCH Assignment Procedure---Abis interface
Physical Context Comfirm

22. TCH Assignment Procedure---Abis interface
System Information Type 5
BA List

23. TCH Assignment Procedure---Abis interface
System Information Type 6
LAC/CI

24. TCH Assignment Procedure---Abis interface
Assignment Command
Frequency Encoding
（Bitmap 0）

25. TCH Assignment Procedure---Abis interface
Frequency Encoding
Fixed Bitmap —— Bitmap 0 —— Use for 1~124 AFRCN

26. TCH Assignment Procedure---Queue and Direct RetryMS
BTS
BSC
MSC
Assignment Request
Queuing Indication
TCH Queue
ST11
ET11
Physical Con Req
At this time, a TCH become free
Assignment Request
Direct Retry
Queuing Indication
ST11
A Handover alarm is raised.
A target BTS is selected T
Channel Activation
ET11
ST9103
Chan. Act. Ack. T
ET9103
HO CMD
HO CMD S
ST3103
The purpose of the Queuing Indication message is to inform the MSC about a delay in the allocation of the necessary dedicated radio resource.
In case of Assignment Procedure, T11 is started (T11 specified the maximum queuing delay and is determined by the operator)
HO Access
ST3124 T
HO Detection
Phys. Info T
ET3124
SABM (FACCH) T
Establish Indication UA T
HO CMP T
HO CMP
ET3103
Assignment Cmp

27. MOC（Early Assignment）MS
BTS
BSC
MSC
RR Connection Establishment
RR Connection Establishment
RR Connection Establishment
ESTIN (CM_Serv_Req)
CM_Serv_Req
（CM Serv Type，Mobile ID，Classmark2，Priority，）
Authentication Procedure
Authentication Procedure
Authentication Procedure
SDCCH
Ciphering Procedure
Ciphering Procedure
Ciphering Procedure
TMSI Realloc Procedure
TMSI Realloc Procedure
TMSI Realloc Procedure
SETUP
SETUP
SETUP
（called party nbr）
Call Proceeding
Call Proceeding
Call Proceeding
Assignment Procedure
Assignment Procedure
Assignment Procedure
Alerting
Alerting
Alerting
Establish TCH first, then connect another part. Alerting transfer on TCH
SETUP : to indicate a mobile Originating Call establishment (contains the call number)
Progress : from the Network to the MS to indicate the progress of a call
Call Proceeding : send by the network to the calling MS to indicate that the requested call establishment information has been receivedand no more call establishment will be accepted
Alerting : to indicate the called user alerting has been initiated
Connect : indicate the call acceptance by the called user
Connect Acknowledge : to acknowledge the offered connection
Connect
Connect
Connect
TCH
Connect Ack.
Connect Ack.
Connect Ack.
Speech

28. MOC —— A interface A interface
Two times Classmark Update, the 1st one is caused by Early Classmark Sending (ECSC); 2nd caused by BSC send Classmark Enquiry

29. MOC —— A interface CM Service Request MOC est/pkt mode con estab
Short message service
Suppl service activation
CLASSMARK

30. MOC —— A interface CLASSMARK Include MS Revision Level
MS Ciphering Capability
MS Frequency Capability
MS RF Power Capability in Each Band

31. MOC —— A interface
CLASSMARK

32. MOC —— A interface
Setup
Called Number

33. MOC（Late Assignment） Speech MS BTS BSC MSC ESTIN (CM_Serv_Req)
RR Connection Establishment
RR Connection Establishment
RR Connection Establishment
ESTIN (CM_Serv_Req)
CM_Serv_Req
Authentication Procedure
Authentication Procedure
Authentication Procedure
Ciphering Procedure
Ciphering Procedure
Ciphering Procedure
TMSI Realloc Procedure
TMSI Realloc Procedure
TMSI Realloc Procedure
SDCCH
SETUP
SETUP
SETUP
Call Proceeding
Call Proceeding
Call Proceeding
Alerting
Alerting
Alerting
Establish another side channel, then setup TCH , Alerting send on SDCCH
Assignment Procedure
Assignment Procedure
Assignment Procedure
Connect
Connect
Connect
Connect Ack.
Connect Ack.
Connect Ack.
TCH
Speech

34. MTC Speech MS BTS BSC MSC Paging Request Paging Command Paging
Paging Group Number: defined by BS_AG_BLKS_RES and BS_PA_MFRMS;MS belong to the Paging Group = (IMSI mod 1000) mod N;MS only monitor its own Paging Group’s Paging Req message
MTC MS
（MS ID（TMSI/IMSI））
（Max 4 TMSI）
BTS
（MS ID（TMSI/IMSI），Paging Group）
BSC
（MS ID（TMSI+IMSI/IMSI），Cell ID（LAC/LAC+CI））
MSC
Paging Request
Paging Command
Paging
ST3113
RR Connection Establishment
RR Connection Establishment
RR Connection Establishment
ESTIN (Paging Resp)
Paging Response
ET3113
（Mobile ID，Classmark2，Priority，）
Authentication Procedure
Authentication Procedure
Authentication Procedure
Ciphering Procedure
Ciphering Procedure
Ciphering Procedure
TMSI Realloc Procedure
TMSI Realloc Procedure
TMSI Realloc Procedure
SETUP
SETUP
SETUP
（calling party nbr）
Call Confirmed
Call Confirmed
Call Confirmed
Assignment Procedure
Assignment Procedure
Assignment Procedure
Alerting
Alerting
Alerting
Connect
Connect
Connect
Connect Ack.
Connect Ack.
Connect Ack.
Speech

35. MTC —— A interface
A-interface

36. MTC —— A interface Paging IMSI, BSC use it for calculate Paging Group
TMSI, it’s save bits number in radio resource for Paging
LAC Paging

37. MTC —— A interface
Paging Response

38. MTC —— A interface
Setup
Calling Number

39. Location Update MS BTS BSC MSC ESTIN (Loc Up Req) Loc Up Req
RR Connection Establishment
RR Connection Establishment
RR Connection Establishment
（LU Type，MS ID，LAI，Classmark1，）
ESTIN (Loc Up Req)
Loc Up Req
ST3210
Authentication Procedure
Authentication Procedure
Authentication Procedure
Ciphering Procedure
Ciphering Procedure
Ciphering Procedure
TMSI Realloc Procedure
TMSI Realloc Procedure
TMSI Realloc Procedure
Loc Up Accept
Loc Up Accept
Loc Up Accept
ET3210
Clear CMD
Channel Release
Channel Release
Three Location Updating tye :
Normal Location updating : used to update the regeistration of the actual LA of a MS in the Network
Periodic Location Updating : to notifiy periodically the availability of the mobile in the network. This procedure is controlled by a timer (T3212) in the MS. The timer is stopped and reset to 0 when : LU accept or Reject message is received, MS has respond to a paging, MS is deactivated.
IMSI Attach : to activate a MS in the Network
If T3210 expires, then T3211 starts. When T3211 reaches 0, the location update procedure is restarted.
Deactivate SACCH
DISC UA
Release Indication
RF Ch Release
RF Ch Release Ack
Clear CMP

40. Location Update —— A interface

41. Location Update —— A interface
Location Update Request
（Follow-on） call procedure
Old LAC
Current TMSI

42. Location Update —— A interface
Location Update Accept
New LAC
Re-allocated TMSI

43. Old TA、MS/BS_TxPwr will be reused in new channel
Intra Cell HO MS
BTS
BSC
MSC
Measurement Rep
Measurement Res
Intra cell HO
Phys Context Req OC
ST9108
Phys Context Conf
ET9108 OC
Old TA、MS/BS_TxPwr will be reused in new channel
Channel Activation NC
ST9103
Channel Activation Ack
ET9103 NC OC
Handover Command
ST3107 OC
Assignment Command
SABM NC NC
Establish Indication UA NC
C10 : incremented when a successfull SDCCH Handover is completed.
C15 : incremented when a RTCH channel has been successfully selected for HO Purpose
C17 : incremented on the target cell when a succesffull RTCH HO is completed.
C39 incremented when an SDCCH subchannel of a TS is selected by the BSS.
Assignment Complete NC
Assignment Complete
ET3107
（HO Cause，Cell ID，Chn Type）
Handover Performed OC
RF Channel Rel
ST_RCR_ACK OC
RF Channel Rel Ack.
ET_RCR_ACK
OC : Old Channel
NC : New Channel

44. Intra Cell HO —— Abis
Abis

45. Intra Cell HO —— Abis
Assignment Command
Old TCH
New TCH Channel

46. Internal Inter Cell HO——Synchronized HOMS
BTSserving
BTStarget
BSC
MSC
Meas Report
Meas Result
HO Alarm & Candidate Cell
Phys Context Req
ST9108
Phys Context Conf
ET9108
Old TA is reused in new channel, but MS/BS_TxPwr will use the MAX in new channel
Channel Activation
ST9103
Channel Act Ack.
ET9103
HO Command
HO Command
（Cell，MA，MAIO，HSN，TS，TA）
ST3103
HO Access
（AB，DCH）
HO Detection
ST3106
C15 : incremented when a RTCH has been successfully selected for HO Purpose.
C10 : incremented when a successfull SDCCH HO has been performed.
C17 : Incremented on the target cell when a successfull RTCH HO is completed
ST200
SABM
ET3106
Establish Ind UA
ET200
Handover Complete
Handover Complete
ST3103
Handover Performed
RF Channel Release
ST_RCR_ACK
RF Channel Rel. Ack.
ET_RCR_ACK

47. Internal Inter Cell HO——asynchronousMS
BTSserving
BTStarget
BSC
MSC
Meas Report
Meas Result
HO Alarm & Candidate Cell
No Physical Cont Req procedure, old channel TA can’t reuse for new channel
Channel Activation
ST9103
Channel Act Ack.
ET9103
HO Command
HO Command
ST3103
HO Access
ST3124
Measure TA
HO Detection
Physical Info
ST3105
ET3124
（TA）
ST200
SABM
（TA is reused）
ET3105
Establish Ind
C15 : incremented when a RTCH has been successfully selected for HO Purpose
C56 : incremented on the serving cell
C52 : incremented on the target cell
ET200 UA
Handover Complete
Handover Complete
ST3103
Handover Performed
Phys Context Req
ST9108
Phys Context Conf
ET9108
RF Channel Release
ST_RCR_ACK
RF Channel Rel. Ack.
ET_RCR_ACK

48. Internal Inter Cell HO——A interface
HO Performed
HO Cause
Target Cell

49. External Inter Cell HO MS BTSserving BTStarget BSCserving BSCtarget
MSC
Meas Report
Meas Result
HO Alarm & Candidate Cell
HO Required
ST_HO_REQ_Lost
HO Request
STrr2
Channel Activation
（SCCP Con Required）
ST9103
Channel Act Ack.
ST9103
HO Request Ack.
ETrr2
HO Command
HO Command
ST9113
（SCCP Con Conf）.
HO Command
ET_HO_REQ_Lost
ST3103
HO Access
ST3124
HO Detection
ST8
Phys Information
ST3106
ET3124
SABM
ST200
ET3106
Establish Ind UA
ET200
T8 : toi supervise the Handover procedure with the MS.
C15 is incremented when a RTCH channel has been successfully for HO Purpose.
Handover Complete
Handover Complete
ET9113
HO Complete
ET3103
RF Channel Release
Clear Command
RF Ch. Rel. Ack.
ET8
Clear Complete
SCCP Released
SCCP Rel. Cmp.

50. External Inter Cell HO---A interface
A interface——outgoing
A interface------incoming

51. External Inter Cell HO——A interface
HO Required
HO Cause
Target Cell

52. External Inter Cell HO——A interface
HO Command
Target cell：BCCH/BSIC
Target cell channel type
Use for HO Access
Initial power for new channel

53. External Inter Cell HO——A interface
Clear Command

54. External Inter Cell HO——A interface
HO Request （1 of 2）
Channel type
encryption
Classmark2

55. External Inter Cell HO——A interface
HO Request （2 of 2）
Source cell
Priority and Queuing
A interface’s CIC
Target cell
Classmark3

56. External Inter Cell HO——A interface
HO Request Ack
HO Command

57. External Inter Cell HO——A interface
HO Complete

58. Channel Release MS release Network release MS BTS BSC MSC Disconnect
Release Complete
Release Complete
Release Complete
Network release
Disconnect
Disconnect
Disconnect
Release
Release
Release
Release Complete
Release Complete
Release Complete

59. Channel Release——A interface
A interface ——MS release
Call release（DTAP layer）
BSSM release
SCCP release
Disconnect
MS release
Normal call clear

60. Channel Release——A interface
A interface ——Network Release
Disconnect
Network release
Another side hung up

61. Channel Release Channel Release Um Channel Release A interface Release
Um and A interface release is separated with each other
Um Channel Release
BSC send Channel Release message to MS
Radio Link Failure
A interface Release
MSC send CLEAR COMMAD to BSC
BSC send CLEAR REQUEST to MSC
The MS receives a Channel Release : the MS instruct the LAPDm function to perform a dsiconnection of the LAPDm and start T3110.
The radio link failure algorithm in the MS is trigerred by the BSS when it stops the sending of SACCH frames to the MS. SACHH frames should be stopped for a period of T3109 for the algorithm in the MS to detect a radio link failure condition. The BSC initiate by sending the DEACTIVATE SACCH to the BTS.
BTS intiated release : when LAPD failure or O&M intervention. In both case, the BTS ensure that the TRX and MS are released and send an ERROR REPORT to the BSC.

62. Channel Release ——Radio ChannelMS
BTS
BSC
MSC
ST3110
Channel Release (DCH)
Deactivate SACCH
DISC (DCH)
Release Indication
ST3111
BSC send Channel Release
To MS UA
ET3110
T3111 Expiry
Phy Context Request
ST9108
Phy Context Confirm
Wait for T3111 expired, then release BTS channel, to ensure the UA message have time to send
ET9108
RF Channel Release
ST_RCR_ACK
RF Channel Release Ack
ET_RCR_ACK
C´hannel Release : cause is included (Normal Release, Abnormal Release (Unspecified, Channel Unacceptable, Timer Expiry, No activity on the Radio Path)).
Disconnect : when the MS doesn't receive any SACCH message, the MS steal some TCH for Signalling (FACCH).
T3111 : this timer allows the exchange of DISC and UA (the process go on when T3111 expires).
Physical Context procedure : by verifying the BS_Power, the BSC detect that the connection is not anymore active.
Radio Link Failure : BTS count the number of missing SACCH frame, when this value reach the Radio Link Time Out, the release procedure starts.
T_RCR_ACK expiry : the BSC attempts the procedure again. In event that this procedure fails again, the BSC will free the channel for reuse and send an O&M error report
No SACCH received from the MS
Connection Fail Ind
Radio Link Failure
RF Channel Release
ST_RCR_ACK
RF Channel Release Ack
ET_RCR_ACK

63. Channel Release ——Abis

64. Channel Release——A Interface Release
BSC
MSC
Clear Request
ST9104
Clear Command
ET9104
BSC Trigger the release
ST9101
Clear Complete
SCCP Released
ET9101
SCCP Released Complete
Clear Command
MSC Trigger the release
Clear Complete
ST9101
SCCP Released
SCCP Released Complete
ET9101

65. Thank You