gsm signaling

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GSM Signaling OverviewGSM Signaling Overview] GSM signaling defines the communications between the mobile and

the network] Signaling has to be carried through the network and across the air-

interface to the mobile] Different protocols are used across different interfaces] All GSM signaling is based on the Open Systems Interconnect (OSI)

model used for computer systems ] The MSC uses ITU’s Signaling System No:7, (SS7 or CCS7) for all its

signaling; to the BSC, HLR, VLR and to other networks ] The Air-interface and A-bis signaling is based on ISDN Link Access

Protocol (LAP-D and LAP-Dm)] Signaling channels are integrated into the air-interface as the BCCH,

PCH, AGCH, SDCCH, SACCH and FACCH] Signaling across all interfaces is specified in the standards to allow

different equipment manufacturers for each unit


Mobile SignalingMobile Signaling] When the mobile is first switched on it is under

the control of its’ own internal algorithms.] It performs the following sequence:

c Search for GSM frequenciesc Find a FCCH and synchronize frequencyc Find a SCH and synchronize timec Listen for a BCCH and download information

about the systemc Download idle neighbor list and make

measurementsc Select a “best server” and camp on itc If the user wants to make a call, the mobile has to

signal to the network. c It does this by sending a “service request” to the

network on the RACH.


GSM SIGNALLINGGSM SIGNALLING

BSC

BTS

MS

LAPD

LAPDm

PLMN(GSM) ISDN

PSTN

Base StationSystem (BSS)

BSSAP

ISUPTUP

MAP

MAP MAPMAP MAP

MAP

VLR AC

VLR HLR EIR

MSC GMSC

SwitchingSystemNSS

SS7 User Parts:•MAP: SS7, Mobile Application Part•BSSAP: SS7, Base Station Sub-System Application Part•ISUP: SS7, International Subscriber User Part•TUP: SS7, Telephone User Part

LAPD: ISDN, Link Access Protocol Version “D”


GSM SignalingGSM Signaling

OSI - Model GSM Equivalent

NETWORK

DATA LINK

PHYSICAL

7

6

5

4

3

2

1

USERTASKS

GSMNETWORKTASKS

Network Messages

Framing / Addressing

Coding / Modulation

APPLICATION

PRESENTATION

SESSION

TRANSPORT

NETWORK

DATA LINK

PHYSICAL

Open Systems Interconnect uses “layers” where only layer 1, the physical layer is actually physically connected between devices. Messages are sent between devices by handing them down to lower layers from transmission across the physical interface.


OSI LayersOSI Layers

Layer 3 Network Layer : Carries signaling messages, for getting the message to its destination. Provides connection oriented (dedicated signaling link) or connectionless services (packet-type signaling). Example: Radio Resource message sent from MSC to BSC.

Layer 2 Data Link Layer :Transfers frames error free between nodes. Concerned with error detection, framing, re-transmission Example: LAPD protocol on A-bis between BSC and BTS.

Layer 1 Physical Layer:Transmits all information across the physical medium. Specifies the physical medium used: mechanical, electrical, functional and procedural characteristics. Example: GMSK modulation on an RF carrier for the Air-interface between the BTS and the MS

Layer 3

Layer 2

Layer 1

Layer 3

Layer 2

Layer 1

Information Flow


Signaling Layers for the Air InterfaceSignaling Layers for the Air InterfaceLayer 1: Functions required to transfer bit steams over physical

TDMA / FDMA channels: j Cipheringj Setting of timing advance & TX powerj Channel Codingj Mapping of logical channels onto physical channels

Layer 2: Provides a reliable signaling link between MS and the network. Protocol is based on the LAPDm of ISDN j Framingj Addressingj Error correction

Layer 3: Takes care of the main control of the MS -network procedures. It is split into 3 sublayers:j Radio Resource Managementj Mobility Managementj Connection Management


AirAir--interface Layersinterface Layers

Reconstruct frames,acknowledges

SpeechSpeech

User DataUser Data

Signaling SignalingOSI layer 3 Network Functions

Builds frames, requestsacknowledgement

OSI layer 2 Data link functions

Channel coding,error protection,interleaving

RFModulation

Error correction,deinterleaving

Equalization

RFDemodulation

Transmitter Receiver

OSI layer 1 Physical layer


Network LayerNetwork Layer] The network layer is split into three sub-layers

c RR - radio resource management: c routes messages to the correct channelsc establishes and maintains physical

connections for control and traffic channels.c MM - mobility management:

c controls authentication and security management.

c provides services for the CM layer.c CM - connection management:

cCC: call control: responsible for establishing, maintaining and releasing calls

c SS: supplementary services: data etcc SMS: short message services

Mobility Management MM

Network LayerLayer 3

Layer 1: Physical Layer

Data Link Layer

CM CC SS SMS

Radio Resources RR


Signaling Protocol Reference ModelSignaling Protocol Reference Model

Note: X.25 can be usedfor transferring O & Minformation

Terminology:DTAP (direct transfer application part)BSSMAP (BSS management application part)BSS OMAP (operation & maintenance application part)SCCP (signaling connection control part)MTP (message transfer part)

To other usersof the SCCPand MTP

To other processeswithin the BSS

To air interfacetransmissionequip.

DTAP BSSMAP

BSSAP

Distribution function

SCCP

MTP

BSSOMAP

Physical Layer

A - Interface

DTAPBSSMAP

Distribution functionBSSOMAP

SCCP

MTP

BSSAP

Other applications,ie. call control

Operation & maintenance info. to OA&M center

BSS NSS


GSM Network Protocol ModelGSM Network Protocol Model

MS BTS BSC MSC

CM

MM

RR

LAPDm

Radio

RR

LAPDm

Radio

Air - Interface A - bis A - Interface

BTSM

LAPD

64 kbit/s

BSSAP

BTSM

LAPD

BSSAP

SCCP

MTP

CM

MM

BSSAP

SCCP

MTP

64 kbit/s

SCCP

64 kbit/s

SCCP

64 kbit/s

Layer 3“Network”

Layer 2“Data Link”

Layer 1“Physical”

The MSC and the mobile always control all the network signaling.


Example “Page Jim”Example “Page Jim”

BTS

Layer 3 message“Page Jim”

Layer 2 selects correct BSC

Layer 1 sends message across 64 kbit signaling channel

BSC Layer 1 receives 64 kbit signaling from MSC

Layer 2 recognizes a message for the mobile and converts to LAPD

Layer 2 selects BTS

Layer 1 sends message across A-bis: T1 or microwave

BTS Layer 1 receives A-bismessage

Layer 2 recognizes a message for the mobile and converts to LAPDm

Layer 2 frames message

Layer 1 sends message on PCH

MS Layer 1 receives PCH

Layer 2 decodes message

Mobile recognizes Layer 3 message“Page Jim” and sends “response to page” BSC

MSC


Radio Resource MessagesRadio Resource Messages

] Radio resource functions are controlled by the BSC and include:c SACCH measurement reporting on the uplinkc System Information messages 5&6 transmitted on the downlinkc Immediate assignment (assignment of SDCCH)c Assignment command (from SDCCH to TCH)cControl of the mobile during handoverc Intra-BSC handoversc Frequency hoppingcChannel mode changescCipheringcChannel release procedurescRadio link failure


Radio Resource MessagesRadio Resource Messages] Assignment request] Assignment complete ] Assignment failure

] Block] Overload] Unblock

] Clear command] Clear complete ] Clear request

] Cipher Mode Command] Cipher Mode Complete

] Handover Request] Handover candidate inquiry] Handover request acknowledge] Handover required] Handover required reject] Handover command] Handover complete] Handover failure

] Paging

] Reset] Queuing] Trace Invocation


System Information MessagesSystem Information Messages] The System Information

Messages are sent to the mobile from the network on the BCCH in Idle mode and on the SACCH in active mode.

] The Physical Information Messages are very similar and are sent on the FACCH after a handover.

] They contain the basic information that the mobile needs to gain access to the network.

] System Information Messages 1 to 4 are sent on the BCCH and rotated with PCH, AGCH, SCH and FCCH, and maybe the SDCCH.

] System Information Messages 5 & 6 are transmitted continuously on the SACCH to active mobiles on the downlink while the measurement report is being sent on the uplink.

] The contents of the System Information Messages are given in the following slides:


System Information MessagesSystem Information Messages] System Information Type 1:1) Cell Channel description (CA)

which gives the ARFCNs used in the cell

2) RACH control parameters which includes:c the maximum number of

retransmissions on the RACHc the number of slots to spread the

transmissionsc the cell barred for access

parameterc call re - establishment allowedc emergency call allowed c control class allowed.

] System Information Type 2:1) Neighbour cells description which

gives the ARFCNs of theneighbour cells to be monitored by the mobile. Note that this is an offset and a bit map listing up to 124 ARFCNs.

2) PLMN permitted which lists: the network colour codes (NCCs) which the mobile can use.

3) the RACH control parameters as System Information Type 1.


System Information MessagesSystem Information Messages] System Information Type 3:1) Cell Identity (CI) to identify any cell

in a given location area2) Location Area Identification

including:c the Mobile Country Code (MCC)c the Mobile Network Code (MNC)c the location area code (LAC)

3) Control channel description including:c the attach / detach parameter (ATT)c the number of blocks reserved for

access grant (AG) c the common control channel

configuration, ie whether it is combined with an SDCCH etc.

4) Cell Options includingc Power Control enabledc DTX enabledc the value of the radio link timeout

counter

5) Cell selection parameters including:c the Cell Reselect Hysteresis parameterc the maximum mobile power on the

control channel MsTxPwrMaxCCH c the minimum access threshold

RXLEVMin.

6) the RACH control parameters as System Information Type 1.


System Information MessagesSystem Information Messages] System Information Type 4:1) Location area identification as in

System Information Type 32) Cell selection parameters as in System

Information Type 33) RACH control parameters as in

System Information Type 14) Cell Broadcast Control Channel

(CBCH) description which gives the description of the channel used for cell broadcast

5) Cell Broadcast Control Channel mobile allocation to give the mobile the ARFCN used for the CBCH

] System Information Type 5:1) Neighbour cells description which

gives the ARFCNs of theneighbour cells to be monitored and reported on by the mobile. Note that this is also an offset and a bit map listing up to 124ARFCNs.


System Information MessagesSystem Information Messages] System Information Type 6:1) Cell Identity (CI) to identify any cell in

a given location area. 2) Location Area Identification including

c the Mobile Country Code (MCC)c the Mobile Network Code (MNC)c the location area code (LAC).

3) Cell Options includingc Power Control enabledc DTX enabledc the value of the radio link timeout counter

4) PLMN permitted which lists the network colour codes (NCCs) which the mobile can use.

] Physical Information Message:

1) Contains the timing advance for the mobile and is sent on the FACCH after a handover if the handover is to another site, ie a non - synchronous handover. It is not sent for a intra-site synchronous handover. (Either between sectors of the same site or a timeslot shuffle)

.


Call Control MessagesCall Control Messages] Call Establishment Messages

c Alerting c Call confirmed c Call proceeding c Connect c Connect Acknowledgec Emergency Setup c Progress c Setup

] Call Clearingc Disconnectc Releasec Release Complete

] Call Information Phase Messagesc Modifyc Modify Completec Modify Rejectc User Information

] Connection Management Messagesc CM Service Acceptc CM Service Rejectc CM Service Requestc CM Re-establishment Request

] Miscellaneous Messagesc Start / Stop DTMF Tonesc Notifyc Status


Mobility Management MessagesMobility Management Messages] Registration Messages

c IMSI Detachc Location Updating Requestc Location Updating Acceptc Location Updating Reject

] Security Messagesc Authentication Requestc Authentication Response c Authentication Rejectc Identity Requestc Identity Responsec TMSI Reallocation Commandc TMSI Reallocation Complete

LAC 1 LAC 2


GSM Cause Codes GSM Cause Codes Rec Rec 2:102:10

Cause Tone(see Table 1)

1 Unassigned number 63 No Route to Destination 66 Channel Unacceptable 616 Normal Clearing 117 User Busy 218 No User Responding 619 User Alerting, No Answer 621 Call Rejected 622 Number Changed -27 Destination out of order 628 Invalid Number Format 630 Response to STATUS ENQUIRY -31 Normal, unspecified -34 No circuit/channel available 338 Network out of order 641 Temporary Failure 342 Switching Equipment Congestion 343 Access Information Discarded 644 Requested circuit/channel not available 3

47 Resources unavailable, unspecified 649 Quality of Service Unavailable 350 Requested facility not subscribed 657 Bearer Capability not authorised 658 Bearer Capability not available 363 Service or option not available, unspecified 665 Bearer Service not implemented 669 Requested Facility not implemented 679 Service or option not implemented, unspecified 681 Invalid Call Reference Value 688 Incompatible Destination 691 Invalid Transit Network Selection 695 Invalid Message, unspecified 696 Mandatory Information Element error 397 Message Type non-existent or not implemented 698 Message not compatible with calls state or

Message Type non-existent or not implemented 699 Information Element non-existent or not implemented 6100 Invalid Information Element contents 6101 Message not compatible with call state 6102 Recovery on timer expiry 6111 Protocol error, unspecified 6127 Interworking, unspecified 6


GSM Supervisory TonesGSM Supervisory TonesTone Frequency Type

1 Dial Tone (optional) 425 Hz Continuous

2 Subscriber Busy 425 Hz Tone on 500ms* (Called Number) Silence 500ms

3 Congestion 425 Hz Tone on 200ms* Silence 500ms

4 Radio Path Acknowledgement 425 Hz Single Tone(Mobile originated only) 200ms(optional)

5 {Radio Path Not Available 425 Hz 200ms} On/off for {Call dropped - Mobile originated only 200ms} 3 bursts

6 Error/Special Information} 950 Hz {Triple Tone* Number Unobtainable } 1400 Hz {Tones on 330ms

Authentication Failure } 1800 Hz {Silence 1.0s

7 Call Waiting Tone 425 Hz, on for 400 ms, 8 s silencefollowed by (425 Hz, on for 150 msoff for 150 ms, on for 150 ms, 8 ssilence and repeated as necessary)


GSM Signaling RecommendationsGSM Signaling Recommendations

Air Interface A - bis A - Interface

Layer 1 protocol“Physical layer”GSM Recs

Layer 2 protocol“Data link layer”GSM Recs

Layer 3 protocol“Network layer”GSM Recs

Radio GMSK

Rec 4:04

64 kbit/s E1, T1,microwaveRec 8:54

CCS764 kbit/s MTPRec 8:04

LAPDm

Rec 4:06

LAPD

Rec 8:56

CCS7 / MTP

Rec 8:06

CM/ MM/ RRDTAPRec 4:08

CM/ MM/ RRBSSMAPRec 8:58

MTP / SCCPBSSAPRec 8:08


GSM TimersGSM Timers] Timers are used to supervise

messages sent across the network.] The network entity sending the

message starts and stops the supervisory timer.

] The mobile uses timers to control its behavior when not under the direct control of the network, for example, when idle, during a handover or during channel disconnect.

] Various messages are used to trigger the start and stop of each timer.

] The timers allow the MS and BTS time to respond to requests for resources or to send information.

] Usually, when a timer times out, the message is re-transmitted.

] If the timer times out again, the channels will be released and a failure will be recorded by the MSC or BSC.

] Timers are classified as:c Radio Resource Timersc Mobility Management Timersc BSSAP Timersc A-bis Timersc Call control Timers

] There are timers for both Layer 3 functions and Layer 2 functions.

GSM Timers

Sue Smith TWSGSM Timers - Radio Resource Timers

4th February '97Name Range Default Comments

NetworkT3101 1 - 5 s 1 s Supervision of network access. Started when IMMEDIATE_ASSIGNMENT is sent to MS. Stops when MS successfully seizes

SDCCH. On expiry, newly allocated channels are released and the access request is forgotten.

T3107 3.5 - 10 s 6 s Supervision of assignment procedure. Started when ASSIGNMENT_CMD is sent to the mobile. Stopped when ASSIGNMENT_COMplete message is received on the new channel or ASSIGNMENT_FAILURE is received on the old channel. On expiry, all resources are released and the connection with the mobile is released.

T3109 5 - 15 s 8 s Releases channels in case of a loss of communication. Started when a lower layer failure is detected by the network when not engaged in a RF procedure. Also used during the channel release procedure. On expiry channels are released. Default is 9 s.

T3111 0.5 s Supervision of channel disconnection. Started when CHANNEL_RELEASE message is sent. On expiry, disconnects the main signalling link. Allows for possible repetition of the disconnection command.

T3113 Supervision of paging procedure. Started when PAGING_REQUEST is sent to the mobile and stopped when PAGING_RESPONSE message is received from the MS. This timer must be longer than T3102 plus T3101. If timer times out, network may allow PAGING_REQUEST to be sent again and the T3113 is re-started.

MobileT3110 0.5 s Used to delay channel deactivation after receipt of the CHANNEL_RELEASE message. Allows some time for disconnection of

main signalling link. Must be short enough to prevent T3109 timing out.

T3120 nRACCH+T1 Supervision of network access attempts. Started when CHANNEL_REQUEST message is sent on the RACCH. Stops on receipt of an IMMEDIATE_ASSIGNMENT on the AGCH. On expiry, if the mobile has not exceeded the maximum number of retransmissions allowed (RET = 4) then the MS sends another CHANNEL_REQUEST and T3120 is loaded with a new value. The value is obtained from T3120 = n RACCH slots + T1 where n = 1..N and N=8 initially and the valaue of "Tx-integer" subsequently, and T1 = 350 ms.

T3122 2 - 255 s 6 s Delays network access. Started on receipt of an IMMEDIATE_ASSIGNMENT_REJECT message from the network. On expiry, the mobile may attempt to access the network again.

TWS Proprietary - www.tws-inc.com - (770) 752-7033

GSM Timers

HandoverT3103 4 - 10 s 6 s Supervises the handover in the BSC. Started when the HANDOVER command is sent to the MS. Stopped when the

HANDOVER_COMPLETE message is received via the new BTS on the new channel or HANDOVER_FAILURE message received via the old BTS on the old channel. On expiry ALL RF channels are released and the mobile is assumed to be lost during the handover procedure.

T3105 100 ms Supervision of repetition frequency of the PHYSICAL INFO message. Started when the network sends the PHYSICAL INFO message to the MS and stopped when any correct frames are received from the MS. On expiry, the PHYSICAL INFO message is sent again up to the number of repetitions (NY1 = 8) and the timer is re-started. If NY1 is reached, the handover is aborted. T3105_F = 100 ms and T3105_D = 280 ms.

T3124 320 ms Supervision of handover in the MS. Started when the MS receives a HANDOVER_CMD and stops when the HANDOVER_COMPLETE message is sent. If the handover fails due to the BTS failing to receive the HANDOVER_ ACCESS message, or the mobile fails to receive the PHYSICAL INFO message, then the Timer expires and a HANDOVER_FAILURE is recorded. The mobile the deactivates the new channels, reactivates the old channels and continues as if no handover attempt had occurred.


GSM Timers

Sue Smith TWSGSM Timers - Mobility Management Timers

4th February 1997Name Range Default Comments

MobileT3210 20 s Started when LOC_UPD_REQ sent. Stopped if LOC_UPD_ACK or LOC_UPD_REJ received from network, or on AUTH_REJ. On

expiry start Timer 3211.

T3211 15 s Started on receipt of LOC_UPD_REJ with cause = network failure. Causes a delay before the mobile attempts access to the network again. On expiry restart location update procedure.

T3212 Time between periodic updates. Started on termination of MM service signalling. Stopped on initiation of MM service signalling. On expiry, initiate location update procedure.

T3213 4 s Started on location update failure. Delays network access attempt. On expiry, generate a new random access attempt.

T3220 5 s Allows time to receive network messages on IMSI Detatach. Started on IMSI_DETACH sent to network. Stopped on release from Radio Management sub-layer. Enter NULL or IDLE into HLR/VLR, not updated.

T3230 15 s Cipher mode supervision. Started on CIPHER_REQUEST sent to BTS. Stopped on CIPHERMODE_SETTING. On expiry, provide RELEASE indication to network.

T3240 10 s Allows time to disconnect from network. Start on normal end of location update procedure. Stop on receipt of any message from the network. On expiry, release RR connection.

NetworkT3250 5 s Start on TMSI_REAL_CMD or LOC_UPD_ACK with new TMSI sent to MS. Stop on TMSI_REAL_COM received. On first expiry,

retransmit AUTH_REQ; on second expiry, release RR connections.

T3260 5 s Supervision of authentication procedure. Start on AUTHentication_REQuest sent to MS. Stop on AUTH_RESP received. On first expiry, retransmit AUTH_REQ; on second expiry, release RR connections.

T3270 5 s Supervision of identity procedure. Start on IDENTITY_REQUEST sent to MS. Stop on IDENTITY_RESPONSE received. On first expiry, re-transmit IDENTITY_REQUEST; on second expiry, release RR connections.


GSM Timers

Sue Smith TWSGSM Timers - BSSAP Timers

4th February 1997Name Range Default Comments

T4 10 - 120 s 60 s Supervision of sending RESET to MSC. Started whenever BSC RESET occurs. Stopped when RESET Acknowledge is received from MSC. On expiry procedure is repeated until RESET ACK is received.

T5 1 - 10 s 4 s Supervision of OVERLOAD procedure. Started when OVERLOAD message is received from MSC. On expiry new OVERLOAD messages are taken into account.

T6 3 - 20 s 10 s Supervision of OVERLOAD procedure. Started with T5 when OVERLOAD message is received from MSC. On expiry traffic is increased to next level.

T7 5 - 30 s 20 s Supervision of periodicity of HANDOVER_REQUIRED message. Started when HANDOVER_REQUIRED message is sent to MSC. Stopped when HANDOVER_COMMAND message is received from MSC. On expiry, handover procedure is repeated.

T8 8 - 15 s 12 s Supervision of handover procedure in source BSC. Started when HANDOVER_COMMAND message is received from MSC. Stopped when CLEAR_COMMAND (external handover) is received from MSC. On expiry, ASSIGNMENT_FAILURE message is sent to MSC.

T10 4 - 14 s 8 s Supervision of assignment procedure. Started when ASSIGNMENT_COMMAND message is sent to the MS via the BTS. Stopped when ASSIGNMENT_COMPLETE or ASSIGNMENT_FAILURE is received from the MS. On expiry, ASSIGNMENT_FAILURE message is sent to MSC.

T12 5 - 30 s 15 s Serves as a guard period for local call clearing procedure. Started when a RESET message is received from the MSC. Stopped when a SSP (sub-system prohibited) message is received from SCCP. On expiry RESET_ACKNOWLEDGEMENT sent to MSC.


GSM Timers

Sue Smith TWSGSM Timers - ABIS Timers


T9101 10 s Non-modifiable


T9104 5 - 20 s 15 s Supervision of clear procedure from MSC. Started when CLEAR_REQ is sent to MSC. Stopped when CLEAR_CMD is received from MSC. On expiry, CHANNEL_REL is sent to mobile, via the BTS.

T9105 2 - 240 s 10 s Supervision of SCCP connection procedure. Started when SCCP_CONNECTION_REQUEST is sent to the MSC. Stopped when SCCP_CONNECTION_CONFIRM or _REFUSED is received from MSC. On expiry, CHANNEL_RELEASE is sent to MS via BTS. Set to 31 s.


T9113 8 - 15 s 12 s Supervision of external handover in target BSC. Started when HANDOVER_REQUEST_ACK is sent to MSC. Stopped when HANDOVER_COMplete is received from MS or when CLEAR_CMD is received from MSC. On expiry CLEAR_REQUEST is sent to MSC.

T200 240 ms Layer 2 repeat timer. Values depend on timers used to supervise message flow between the MS and the network. For proper operation T200 should be greater than the maximum time between re-transmission of command frames and the reception of their corresponding response or acknowledgement frames but should be shorter than the corresponding Layer 3 timer supervising this message flow.


GSM Timers

Sue Smith TWSGSM Timers - MSC Timers


TNT1 60 - 300 s 300 s Timer deployed to ensure release of SCCP resources. Internal SCCP Integrity Timer

TNT2 1 - 30 s 5 s ASSIGNMENT_REQUEST message sent, awaiting for ASSIGNMENT_COMPLETE reply from BSS. On expiry channels are released. Value of TNT2 should be greater than BSS timer T10.

TNT3 1 - 30 s 5 s CLEAR_COMMAND message sent, awaiting CLEAR_COMPLETE reply from BSS. On expiry resources are released and mobile is assumed lost during call clear. Value of TNT3 + T102 should be greater than T8 at the BSS.

TNT4 1 - 30 s 5 s CIPHER_MODE_COMMAND message sent, awaiting CIPHER_MODE_COMPLETE reply from BSS. On expiry the connection is released and a cipher failure is logged (GMSC601 log).

T101 1 - 10 s 5 s At MSC-A, HANDOVER_REQUEST message sent, awaiting HANDOVER_REQUEST_ACKNOWLEDGEMENT from BSS. If T101 expires, the MSC tries to use another cell from the list of preferred cells. (see NPC parameter)

T201 1 - 30 s 5 s At MSC-B, HANDOVER_REQUEST message sent, awaiting HANDOVER_REQUEST_ACKNOWLEDGEMENT message at MSC-B after inter-MSC handover. If T201 expires the MSC attempts to use another cell from the preferred cell list if available.

T102 1 - 30 s 5 s With T103, T104, T202, T204, T210 these supervise the sending of messages between two MSCs for an inter-MSC handover. On expiry resources are released (similar to inter-BSC handover supervisory timers)

T3250 1 - 20 s 5 s TMSI_REALLOCATE_COMMAND or LOCATION_UPDATE_ACCEPT message sent, awaiting TMSI_REALLOCATE command from mobile station. On initial expiry message re-sent, on second expiry release connection.

T3260 1 - 20 s 5 s AUTHENTIATION_REQUEST message sent, awaiting AUTHENTICATION_RESPONSE message from mobile. On initial expiry message re-sent, on second expiry release connection.

T3270 1 - 20 s 5 s IDENTITY_REQUEST message sent, awaiting IDENTITY_RESPONSE message from mobile. On initial expiry message re-sent, on second expiry release connection.

T2_DTAP 30 - 120 s 30 s Call initiated to mobile station and no response message is received. Incoming call timer for network side integrity. On expiry, release connection.

T301 45 - 300 s 180 s ALERT message is received for the mobile, awaiting sending of CALL_CONFIRMED message. On expiry, release connection.


GSM Timers

T303 1 - 60 s 30 s SETUP message is received for the mobile station, awaiting sending of CALL_CONFIRMED message. On expiry, release connection.

T305 1 - 60 s 30 s DISCONNECT message sent to mobile, awaiting RELEASE_COMPLETE from the mobile. On expiry RELEASE message sent.

T308 1 - 60 s 30 s RELEASE message sent to the mobile. Awaiting ALERT, CONNECT or DISCONNECT message from the network. On expiry, DISCONNECT sent.

T310 1 - 60 s 30 s CALL_CONFIRMED message is sent to the mobile, awaiting ALERT, CONNECT or DISCONNECT message from the network. On expiry, DISCONNECT sent.

T313 1 - 60 s 30 s CONNECT message has been sent to the mobile, awaiting reply of CONNECT_ACKNOWLEDGEMENT. On expiry, DISCONNECT sent.

TC1N 1 - 60 s 20 s CP_DATA_INDICATION sent to the mobile, awaiting reply of CP_ACKNOWLEDGEMENT. Error indication on second expiry.


MS

CALL SET-UP - Mobile TerminateBTS

CHANNEL REQUEST (RACH)

IMMEDIATE ASSIGNMENT (AGCH)

UA (PAGING RESPONSE)

CHANNEL REQUIRED

CHANNEL ACTIVATION ACK

IMMEDIATE ASSIGN COMMAND

DATA INDICATION

BSC

PAGING REQUEST (PCH)

SABM (PAGING RESPONSE)

(SDCCH)

(SDCCH)

ASSIGNMENT COMMAND (SDCCH)

SABM (FACCH) call confirmed

UA call proc.

ASSIGNMENT COMPLETE (CM)

ALERTING

CONNECT

CONNECT ACK

DISCONNECT

RELEASE

RELEASE COMPLETE

CHANNEL RELEASE

DISC

UA

T3120

RR nRACCH

+ T1 (350ms)

IMM ASSIGN RES

T3122 (6s)

T3110

0.5s

MOBILE DISCONNECT

PAGING COMMAND CM

(IMMEDIATE ASSIGNMENT)CHANNEL ACTIVATION

RR

ESTABLISH INDICATION RR

PHYSICAL CONTEXT REQUEST

PHYSICAL CONTEXT CONFIRM

CHANNEL ACTIVATION (TCH ASSIGN)

CHANNEL ACT. ACK

DATA REQUEST (CM)

ESTABLISH INDICATION

RF CHANNEL RELEASE (SDCCH) RR

RF CHANNEL RELEASE ACK RR

DATA REQUEST

DATA REQUEST

DATA INDICATION

DATA INDICATION

DATA REQUEST

DATA INDICATION

DATA REQUEST

DEACTIVATE SACCH

RELEASE INDICATION

RF CHANNEL RELEASE

RR MM CM

BSS MAP

T3101

(RR) 1s

T3113

(RR)

>T3101 + T3120

T3107

6s

T3111

0.5s

LAYER 2 TIMERS

T200 240ms x 4 rep.

THEN T3109 (8s) RELEASES LOWER LAYER.

T10

8s

MSC

PAGING COMMAND CM

PAGE RESPONSE CM

SETUP

ASSIGNMENT REQUEST COMMAND CM

ASSIGNMENT COMPLETE CM

CLEAR REQUEST

CLEAR COMMAND

CLEAR COMPLETE

on RF channel release

or T3111 expiry

TNT3

(5s)

TNT2

(5s)

TNT2 should be

greater than T10

RF CHANNEL RELEASE ACK

AUTHENTICATE REQUEST (RAND)AUTHENTICATE

AUTHENTICATE REQPONSE AUTHENTICATE RESPONSE (SRES)

CIPHER MODE COMMANDCIPHER MODE CMD

CIPHER MODE COMPLETE CIPHER MODE COMPLETE

SETUP

CALL PROCEEDING CALL PROCEEDING

ALERTING

CONNECT

CONNECT ACKNOWLEDGE

(FACCH)

(FACCH on TCH)

CHANNEL RELEASE

RELEASE COMPLETE

Air InterfaceA-bis

A-Interface

T301

T303

T308

T310

T313

TNT4

TW

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Mobile

INTER - BSC HANDOVERBTS 2

MEASUREMENT REPORT

BSC 1

SYS INFO 5 & 6

UA

BTS MEAS. RESULT

RR MM CM BSS MAP

T7 20s

T3113

6s

H/O FAILS

T3124 TIMES OUT

SABM

H/O FAILURE

Return to Old channel

(SACCH)

HANDOVER COMMAND

MS MEAS. RESULT

DATA REQUEST

RELEASE REQUEST

RF CHAN. RELEASE

RF CHAN. REL. ACK

OLD BSC

T8

12s

T8 +T102 + TNT3

HANDOVER REQUIRED

HANDOVER COMMAND

CLEAR COMMAND

CLEAR COMPLETE

HANDOVER FAILURE

MSC

HANDOVER REQUEST

H/O REQ. ACK.

H/O COMPLETE

RR MM CM BSS MAP

T9113

12s

T101

Def: 5s

T102

Def: 5s

TNT3

CLEAR COMMAND

CLEAR COMPLETE

TNT3

(5s)NEW BSC

BSC 2

CHANNEL ACTIVATION

ACT. ACK.

HANDOVER DETECT

ESTABLISH INDICATION

RELEASE RF CHANNEL

RF CH. REL. ACK.

BTS 1

HANDOVER ACCESS

PHYSICAL INFO

PHYSICAL INFO

SABM

UA

HANDOVER COMPLETE

T3105 100ms

T3124

320ms

Mobile

(FACCH)

HANDOVER ACCESS

(FACCH)

Air InterfaceA-bis A-Interface A-Interface A-bis

Air Interface

Note: Handover Accesson FACCH usingRACCH burst structure

No Phys Infoon SynchronisedHandovers

(FACCH)

DATA INDICATION

RELEASE

RELEASE COMPLETE

RELEASE COMPLETE

RELEASE

DATA INDICATION

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LOCATION UPDATEBTS

T3210

20s

T3230

15s

T3240

10s

CHANNEL REQUEST (RACH)

IMMEDIATE ASSIGNMENT (AGCH)

CM SERVICE REQUEST (LOC UPDATE)

IDENTITY REQUEST

IDENTITY RESPONSE

AUTHENTICATION REQUEST

AUTHENTICATION RESPONSE

CIPHER MODE COMMAND

CIPHER MODE COMPLETE

LOC UPDATE ACCEPTED

TMSI REALLOCATION COMPLETE

RELEASE

RELEASE COMPLETE

CHANNEL REQUIRED

CHANNEL ACTIVATION

CHANNEL ACTIVATION ACK

IMMEDIATE ASSIGNMENT

T3250

5SCHANNEL RELEASE

RELEASE COMPLETE

DEACTIVATE SDCCH

RELEASE RF CHANNEL

RF CHANNEL RELEASE ACK.

BSC MSC

LOCATION UPDATE REQUEST CM

IDENTITY REQUEST

IDENTITY RESPONSE

AUTH. REQUEST (RAND)

AUTH. RESPONSE (SRES)

CIPHER MODE CMD (Key)

CIPHER MODE COMPLETE

LOC UPDATE ACCEPTED

TMSI REALLOCATION COMPLETE

CLEAR COMMAND

(TMSI)

CLEAR COMPLETE

VLR

VLR

VLR

TMSI

ACKNOWLEDGE

TMSI, LOC AREA ACCEPTED

TMSI

ACKNOWLEDGE

UPDATE LOCATION AREA

T3210

20s

T3240

10s

T3230

15s

RR / CM / MM BSSMAP

T3111

T3260

5s

T3270

5s

T3250

5S

TNT 4

(5S)

TNT 3

(5S)

SRES

S.Smith Dec ‘94

(SDCCH)

T3260

T3250

T3270

Air InterfaceA-bis

A-Interface

RELEASE INDICATION

DISC

UA

RELEASED

RELEASE COMPLETE

CHANNEL RELEASE

(SDCCH)

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gsm signaling

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