Gsm signaling

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Gsm signaling

  1. 1. GSM 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 TWS Proprietary - www.tws -inc.com - (770) 752-7033
  2. 2. Mobile 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 frequencies c Find a FCCH and synchronize frequency c Find a SCH and synchronize time c Listen for a BCCH and download information about the system c Download idle neighbor list and make measurements c Select a “best server” and camp on it c 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. TWS Proprietary - www.tws -inc.com - (770) 752-7033
  3. 3. GSM SIGNALLING Switching SystemVLR AC NSS MAP MAP MAP MAPVLR HLR EIR MAP MAPMSC ISUP GMSC PSTN TUP BSSAP Base StationBSC System (BSS) PLMN LAPD (GSM) ISDNBTS SS7 User Parts: •MAP: SS7, Mobile Application Part LAPDm •BSSAP: SS7, Base Station Sub-System Application PartMS •ISUP: SS7, International Subscriber User Part •TUP: SS7, Telephone User Part LAPD: ISDN, Link Access Protocol Version “D” TWS Proprietary - www.tws -inc.com - (770) 752-7033
  4. 4. GSM SignalingOpen Systems Interconnect uses “layers” where only layer 1, the physicallayer is actually physically connected between devices. Messages are sentbetween devices by handing them down to lower layers from transmissionacross the physical interface. OSI - Model GSM Equivalent 7 APPLICATION USER 6 PRESENTATION TASKS 5 SESSION 4 TRANSPORT 3 NETWORK NETWORK Network Messages GSM 2 DATA LINK DATA LINK Framing / Addressing NETWORK PHYSICAL Coding / Modulation TASKS 1 PHYSICAL TWS Proprietary - www.tws -inc.com - (770) 752-7033
  5. 5. OSI Layers Layer 3 Network Layer : Carries signaling messages, for getting the message toLayer 3 Layer 3 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 Layer 2 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 Layer 1 Layer 1 Physical Layer: Transmits all information across the physical medium. Specifies the physical medium used: mechanical, Information Flow electrical, functional and procedural characteristics. Example: GMSK modulation on an RF carrier for the Air-interface between the BTS and the MS TWS Proprietary - www.tws -inc.com - (770) 752-7033
  6. 6. Signaling Layers for the Air InterfaceLayer 1: Functions required to transfer bit steams over physical TDMA / FDMA channels: j Ciphering j Setting of timing advance & TX power j Channel Coding j Mapping of logical channels onto physical channelsLayer 2: Provides a reliable signaling link between MS and the network. Protocol is based on the LAPDm of ISDN j Framing j Addressing j Error correctionLayer 3: Takes care of the main control of the MS -network procedures. It is split into 3 sublayers: j Radio Resource Management j Mobility Management j Connection Management TWS Proprietary - www.tws -inc.com - (770) 752-7033
  7. 7. Speech Air-interface Layers Speech User Data User Data Signaling OSI layer 3 Network Functions Signaling OSI layer 2 Data link functionsBuilds frames, requestsacknowledgement Reconstruct frames, acknowledges Channel coding, error protection, Error correction, interleaving deinterleaving OSI layer 1 Physical layer Equalization Transmitter Receiver RF RF Modulation Demodulation TWS Proprietary - www.tws -inc.com - (770) 752-7033
  8. 8. Network Layer] The network layer is split into three sub-layers Network Layer c RR - radio resource management: Layer 3 c routes messages to the correct channels CM CC SS SMS c establishes and maintains physical connections for control and traffic channels. c MM - mobility management: Mobility Management MM c controls authentication and security management. Radio Resources RR c provides services for the CM layer. c CM - connection management: Data Link Layer c CC: call control: responsible for establishing, maintaining and releasing calls Layer 1: Physical Layer c SS: supplementary services: data etc c SMS: short message services TWS Proprietary - www.tws -inc.com - (770) 752-7033
  9. 9. Signaling Protocol Reference Model BSS NSSTo other processes Other applications,within the BSS A - Interface ie. call control BSSAP BSSAP Operation & maintenance info. to BSS BSSTo air interface DTAP DTAP OA&M center MAP MAPtransmissionequip. BSS BSS Distribution function Distribution function OMAP OMAP SCCP SCCP To other users MTP MTP of the SCCP and MTP Physical Layer Terminology: DTAP (direct transfer application part) BSSMAP (BSS management application part) BSS OMAP (operation & maintenance application part) Note: X.25 can be used SCCP (signaling connection control part) for transferring O & M MTP (message transfer part) information TWS Proprietary - www.tws -inc.com - (770) 752-7033
  10. 10. GSM Network Protocol Model The MSC and the mobile always control all the network signaling. MS BTS BSC MSC CM Layer 3 CM MM“Network” MM BSSAP BSSAP BSSAP RR RR BTSM BTSM SCCP SCCP Layer 2“Data Link” LAPDm LAPDm LAPD LAPD MTP MTP Layer 1 Radio Radio 64 kbit/s 64 kbit/s 64 kbit/s 64 kbit/s“Physical” Air - Interface A - bis A - Interface TWS Proprietary - www.tws -inc.com - (770) 752-7033
  11. 11. Example “Page Jim”Mobile recognizesLayer 3 message Layer 3 message“Page Jim” and “Page Jim”sends “response topage” MSC BSC Layer 2 Layer 2 Layer 2 recognizes a Layer 2 recognizes a Layer 2 frames message for selects message for the selects Layer 2 message the mobile and BTS mobile and correct BSC decodes converts to converts to message LAPDm LAPD BTS Layer 1 sendsMS Layer 1 BSC Layer 1 Layer 1 sends Layer 1 messagereceives BTS Layer 1 receives 64 kbit message across sends across A-bis:PCH receives A-bis signaling from 64 kbit signaling message T1 or message MSC channel on PCH microwave TWS Proprietary - www.tws -inc.com - (770) 752-7033
  12. 12. Radio Resource Messages] Radio resource functions are controlled by the BSC and include: c SACCH measurement reporting on the uplink c System Information messages 5&6 transmitted on the downlink c Immediate assignment (assignment of SDCCH) c Assignment command (from SDCCH to TCH) c Control of the mobile during handover c Intra-BSC handovers c Frequency hopping c Channel mode changes c Ciphering c Channel release procedures c Radio link failure TWS Proprietary - www.tws -inc.com - (770) 752-7033
  13. 13. Radio Resource Messages] Assignment request ] Handover Request] Assignment complete ] Handover candidate inquiry] Assignment failure ] Handover request acknowledge ] Handover required] Block ] Handover required reject] Overload ] Handover command] Unblock ] Handover complete ] Handover failure] Clear command] Clear complete ] Paging] Clear request ] Reset] Cipher Mode Command ] Queuing] Cipher Mode Complete ] Trace Invocation TWS Proprietary - www.tws -inc.com - (770) 752-7033
  14. 14. System Information Messages] The System Information ] System Information Messages 1 to Messages are sent to the 4 are sent on the BCCH and rotated mobile from the network on the with PCH, AGCH, SCH and FCCH, BCCH in Idle mode and on the and maybe the SDCCH. SACCH in active mode. ] System Information Messages 5 &] The Physical Information 6 are transmitted continuously on Messages are very similar and the SACCH to active mobiles on the are sent on the FACCH after a downlink while the measurement handover. report is being sent on the uplink.] They contain the basic ] The contents of the System information that the mobile Information Messages are given in needs to gain access to the the following slides: network. TWS Proprietary - www.tws -inc.com - (770) 752-7033
  15. 15. System Information Messages] System Information Type 1: ] System Information Type 2:1) Cell Channel description (CA) 1) Neighbour cells description which which gives the ARFCNs used in gives the ARFCNs of the the cell neighbour cells to be monitored2) RACH control parameters which by the mobile. Note that this is an includes: offset and a bit map listing up to c the maximum number of 124 ARFCNs. retransmissions on the RACH 2) PLMN permitted which lists: the c the number of slots to spread the network colour codes (NCCs) transmissions which the mobile can use. c the cell barred for access 3) the RACH control parameters as parameter System Information Type 1. c call re - establishment allowed c emergency call allowed c control class allowed. TWS Proprietary - www.tws -inc.com - (770) 752-7033
  16. 16. System Information Messages] System Information Type 3: 4) Cell Options including1) Cell Identity (CI) to identify any cell c Power Control enabled in a given location area c DTX enabled c the value of the radio link timeout2) Location Area Identification counter including: 5) Cell selection parameters c the Mobile Country Code (MCC) including: c the Mobile Network Code (MNC) c the Cell Reselect Hysteresis parameter c the location area code (LAC) c the maximum mobile power on the3) Control channel description control channel MsTxPwrMaxCCH including: c the minimum access threshold c the attach / detach parameter (ATT) RXLEVMin. c the number of blocks reserved for 6) the RACH control parameters as access grant (AG) System Information Type 1. c the common control channel configuration, ie whether it is combined with an SDCCH etc. TWS Proprietary - www.tws -inc.com - (770) 752-7033
  17. 17. System Information Messages] System Information Type 4:1) Location area identification as in System Information Type 3 ] System Information Type 5:2) Cell selection parameters as in System 1) Neighbour cells description which Information Type 3 gives the ARFCNs of the3) RACH control parameters as in neighbour cells to be monitored System Information Type 1 and reported on by the mobile.4) Cell Broadcast Control Channel Note that this is also an offset (CBCH) description which gives the and a bit map listing up to 124 description of the channel used for ARFCNs. cell broadcast5) Cell Broadcast Control Channel mobile allocation to give the mobile the ARFCN used for the CBCH TWS Proprietary - www.tws -inc.com - (770) 752-7033
  18. 18. System Information Messages] System Information Type 6:1) Cell Identity (CI) to identify any cell in ] Physical Information a given location area. Message:2) Location Area Identification including 1) Contains the timing advance c the Mobile Country Code (MCC) for the mobile and is sent on c the Mobile Network Code (MNC) the FACCH after a handover c the location area code (LAC). if the handover is to another3) Cell Options including site, ie a non - synchronous c Power Control enabled handover. It is not sent for a c DTX enabled intra-site synchronous c the value of the radio link timeout counter handover. (Either between4) PLMN permitted which lists the sectors of the same site or a network colour codes (NCCs) which timeslot shuffle) the mobile can use. . TWS Proprietary - www.tws -inc.com - (770) 752-7033
  19. 19. Call Control Messages] Call Establishment Messages ] Call Information Phase Messages c Alerting c Modify c Call confirmed c Modify Complete c Call proceeding c Modify Reject c Connect c User Information c Connect Acknowledge c Emergency Setup ] Connection Management Messages c Progress c CM Service Accept c Setup c CM Service Reject c CM Service Request] Call Clearing c CM Re-establishment Request c Disconnect c Release ] Miscellaneous Messages c Release Complete c Start / Stop DTMF Tones c Notify c Status TWS Proprietary - www.tws -inc.com - (770) 752-7033
  20. 20. Mobility Management Messages] Registration Messages c IMSI Detach c Location Updating Request c Location Updating Accept c Location Updating Reject LAC 1 LAC 2] Security Messages c Authentication Request c Authentication Response c Authentication Reject c Identity Request c Identity Response c TMSI Reallocation Command c TMSI Reallocation Complete TWS Proprietary - www.tws -inc.com - (770) 752-7033
  21. 21. GSM Cause Codes Rec 2:10Cause Tone 47 Resources unavailable, unspecified 6 (see Table 1) 49 Quality of Service Unavailable 31 Unassigned number 6 50 Requested facility not subscribed 63 No Route to Destination 6 57 Bearer Capability not authorised 6 58 Bearer Capability not available 36 Channel Unacceptable 6 63 Service or option not available, unspecified 616 Normal Clearing 1 65 Bearer Service not implemented 617 User Busy 2 69 Requested Facility not implemented 618 No User Responding 6 79 Service or option not implemented, unspecified 619 User Alerting, No Answer 6 81 Invalid Call Reference Value 621 Call Rejected 6 88 Incompatible Destination 622 Number Changed - 91 Invalid Transit Network Selection 627 Destination out of order 6 95 Invalid Message, unspecified 628 Invalid Number Format 6 96 Mandatory Information Element error 330 Response to STATUS ENQUIRY - 97 Message Type non-existent or not implemented 631 Normal, unspecified - 98 Message not compatible with calls state or Message Type non-existent or not implemented 634 No circuit/channel available 3 99 Information Element non-existent or not implemented 638 Network out of order 6 100 Invalid Information Element contents 641 Temporary Failure 3 101 Message not compatible with call state 642 Switching Equipment Congestion 3 102 Recovery on timer expiry 643 Access Information Discarded 6 111 Protocol error, unspecified 644 Requested circuit/channel not available 3 127 Interworking, unspecified 6 TWS Proprietary - www.tws -inc.com - (770) 752-7033
  22. 22. GSM Supervisory TonesTone Frequency Type1 Dial Tone (optional) 425 Hz Continuous2 Subscriber Busy 425 Hz Tone on 500ms* (Called Number) Silence 500ms3 Congestion 425 Hz Tone on 200ms* Silence 500ms4 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 bursts6 Error/Special Information} 950 Hz {Triple Tone* Number Unobtainable } 1400 Hz {Tones on 330ms Authentication Failure } 1800 Hz {Silence 1.0s7 Call Waiting Tone 425 Hz, on for 400 ms, 8 s silence followed by (425 Hz, on for 150 ms off for 150 ms, on for 150 ms, 8 s silence and repeated as necessary) TWS Proprietary - www.tws -inc.com - (770) 752-7033
  23. 23. GSM Signaling Recommendations Air Interface A - bis A - Interface Layer 1 protocol Radio GMSK 64 kbit/s E1, T1, CCS7 “Physical layer” microwave 64 kbit/s MTP GSM Recs Rec 4:04 Rec 8:54 Rec 8:04 Layer 2 protocol LAPDm LAPD CCS7 / MTP “Data link layer” GSM Recs Rec 4:06 Rec 8:56 Rec 8:06 Layer 3 protocol CM/ MM/ RR CM/ MM/ RR MTP / SCCP “Network layer” DTAP BSSMAP BSSAP GSM Recs Rec 4:08 Rec 8:58 Rec 8:08 TWS Proprietary - www.tws -inc.com - (770) 752-7033
  24. 24. GSM Timers] Timers are used to supervise ] Usually, when a timer times out, messages sent across the network. the message is re-transmitted.] The network entity sending the ] If the timer times out again, the message starts and stops the channels will be released and a supervisory timer. failure will be recorded by the] The mobile uses timers to control its MSC or BSC. behavior when not under the direct ] Timers are classified as: control of the network, for example, c Radio Resource Timers when idle, during a handover or during c Mobility Management Timers channel disconnect. c BSSAP Timers] Various messages are used to trigger c A-bis Timers the start and stop of each timer. c Call control Timers] The timers allow the MS and BTS time ] There are timers for both Layer 3 to respond to requests for functions and Layer 2 functions. resources or to send information. TWS Proprietary - www.tws -inc.com - (770) 752-7033
  25. 25. GSM Timers Sue Smith TWS GSM Timers - Radio Resource Timers 4th February 97 Name Range Default CommentsNetwork T3101 1-5s 1s 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 6s 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 8s 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 6s 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
  26. 26. GSM TimersHandover T3103 4 - 10 s 6s 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. TWS Proprietary - www.tws-inc.com - (770) 752-7033
  27. 27. GSM Timers Sue Smith TWS GSM Timers - Mobility Management Timers 4th February 1997 Name Range Default CommentsMobileT3210 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 4s Started on location update failure. Delays network access attempt. On expiry, generate a new random access attempt. T3220 5s 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.Network T3250 5s 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 5s 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 5s 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. TWS Proprietary - www.tws-inc.com - (770) 752-7033
  28. 28. GSM Timers Sue Smith TWS GSM 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 4s 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 8s 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. TWS Proprietary - www.tws-inc.com - (770) 752-7033
  29. 29. GSM Timers Sue Smith TWS GSM Timers - ABIS Timers 4th February 97Name Range Default CommentsT9101 10 s Non-modifiableT9103 2s Non-modifiableT9104 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.T9108 2s Non-modifiableT9113 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. TWS Proprietary - www.tws-inc.com - (770) 752-7033
  30. 30. GSM Timers Sue Smith TWS GSM Timers - MSC Timers 4th February 97 Name Range Default Comments TNT1 60 - 300 s 300 s Timer deployed to ensure release of SCCP resources. Internal SCCP Integrity Timer TNT2 1 - 30 s 5s 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 5s 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 5s 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 5s 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 5s 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 5s 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 5s 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 5s 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 5s 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. TWS Proprietary - www.tws-inc.com - (770) 752-7033
  31. 31. GSM TimersT303 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. TWS Proprietary - www.tws-inc.com - (770) 752-7033
  32. 32. CALL SET-UP - Mobile Terminate MS BTS BSC MSC RR MM BSS MAP CM PAGING REQUEST (PCH) PAGING COMMAND CM PAGING COMMAND CM CHANNEL REQUEST (RACH) T3113 CHANNEL REQUIRED T3120 (RR) CHANNEL ACTIVATION (IMMEDIATE ASSIGNMENT) RR nRACCH >T3101 + T3120 + T1 (350ms) CHANNEL ACTIVATION ACK IMM ASSIGN RES IMMEDIATE ASSIGNMENT (AGCH) IMMEDIATE ASSIGN COMMAND RR T3122 (6s) SABM (PAGING RESPONSE) (SDCCH) PAGE RESPONSE CM T3101 UA (PAGING RESPONSE) (SDCCH) (RR) 1s ESTABLISH INDICATION RRTWS Proprietary - www.tws -inc.com - (770) 752-7033 AUTHENTICATE AUTHENTICATE REQUEST (RAND) AUTHENTICATE REQPONSE AUTHENTICATE RESPONSE (SRES) CIPHER MODE CMD CIPHER MODE COMMAND TNT4 CIPHER MODE COMPLETE CIPHER MODE COMPLETE SETUP PHYSICAL CONTEXT REQUEST SETUP T303 CALL PROCEEDING PHYSICAL CONTEXT CONFIRM CALL PROCEEDING LAYER 2 TIMERS CHANNEL ACTIVATION (TCH ASSIGN) T200 240ms x 4 rep. T310 THEN T3109 (8s) CHANNEL ACT. ACK RELEASES LOWER LAYER. ASSIGNMENT COMMAND (SDCCH) DATA REQUEST (CM) ASSIGNMENT REQUEST COMMAND CM (FACCH on TCH) SABM (FACCH) call confirmed TNT TNT2 should be T10 T3107 2 greater than T10 6s 8s UA call proc. (5s) ESTABLISH INDICATION DATA INDICATION CM ASSIGNMENT COMPLETE (CM) ASSIGNMENT COMPLETE RF CHANNEL RELEASE (SDCCH) RR RF CHANNEL RELEASE ACK RR ALERTING (FACCH) DATA REQUEST ALERTING T301 CONNECT DATA REQUEST CONNECT CONNECT ACK DATA INDICATION CONNECT ACKNOWLEDGE T313 MOBILE DISCONNECT DISCONNECT DATA INDICATION CLEAR REQUEST RELEASE DATA REQUEST CLEAR COMMAND TNT3 RELEASE COMPLETE DATA INDICATION CLEAR COMPLETE (5s) CHANNEL RELEASE DATA REQUEST CHANNEL RELEASE T3110 0.5s DEACTIVATE SACCH T3111 T308 DISC RELEASE INDICATION 0.5s RELEASE COMPLETE UA RF CHANNEL RELEASE on RF channel release RF CHANNEL RELEASE ACK or T3111 expiry Air Interface A-Interface A-bis
  33. 33. INTER - BSC HANDOVER Mobile BTS 1 BSC 1 MSC BSC 2 BTS 2 Mobile RR MM CM BSS MAP RR MM CM BSS MAP SYS INFO 5 & 6 BTS MEAS. RESULT (SACCH) MEASUREMENT REPORT MS MEAS. RESULT T7 20s HANDOVER REQUIRED HANDOVER REQUEST CHANNEL ACTIVATION T101 ACT. ACK. Def: 5s H/O REQ. ACK. (FACCH) Note: Handover Access HANDOVER DETECT HANDOVER ACCESS on FACCH HANDOVER COMMAND DATA REQUEST HANDOVER COMMAND using T9113 RACCH burst (FACCH) PHYSICAL INFO structure RELEASE REQUEST T8 12sTWS Proprietary - www.tws -inc.com - (770) 752-7033 T3113 T3105 12s 100ms PHYSICAL INFO 6s T102 No Phys Info ESTABLISH INDICATION on Synchronised SABM Handovers T8 +T102 + Def: 5s TNT3 T3124 UA 320ms HANDOVER H/O COMPLETE DATA INDICATION COMPLETE CLEAR COMMAND TNT3 CLEAR COMPLETE RF CHAN. RELEASE RELEASE RF CHAN. REL. ACK Air Interface RELEASE COMPLETE H/O FAILS T3124 TIMES OUT HANDOVER ACCESS (FACCH) SABM UA DATA INDICATION HANDOVER FAILURE OLD BSC H/O FAILURE Return to Old CLEAR COMMAND channel TNT3 NEW BSC (5s) CLEAR COMPLETE RELEASE RELEASE RF CHANNEL RELEASE COMPLETE RF CH. REL. ACK. Air Interface A-bis A-Interface A-Interface A-bis
  34. 34. LOCATION UPDATE Mobile BTS BSC MSC RR / CM / MM BSSMAP CHANNEL REQUEST (RACH) CHANNEL REQUIRED CHANNEL ACTIVATION CHANNEL ACTIVATION ACK IMMEDIATE ASSIGNMENT (AGCH) IMMEDIATE ASSIGNMENT CM SERVICE REQUEST (LOC UPDATE) LOCATION UPDATE REQUEST CM (SDCCH) VLR ( SDCCH) UPDATE LOCATION AREATWS Proprietary - www.tws -inc.com - (770) 752-7033 IDENTITY REQUEST IDENTITY REQUEST T T3270 3 T3230 5s T3270 2 IDENTITY RESPONSE IDENTITY RESPONSE 15s 3 VLR TMSI 0 ACKNOWLEDGE 1 5 s AUTHENTICATION REQUEST AUTH. REQUEST (RAND) T T3260 T3260 3 SRES 5s 2 AUTHENTICATION RESPONSE AUTH. RESPONSE (SRES) VLR 1 0 TMSI, LOC AREA ACCEPTED 2 0 CIPHER MODE COMMAND CIPHER MODE CMD (Key) s TNT 4 CIPHER MODE COMPLETE CIPHER MODE COMPLETE (5S) T3210 20s LOC UPDATE ACCEPTED T LOC UPDATE ACCEPTED (TMSI) 3 T3250 2 5 T3250 TMSI REALLOCATION COMPLETE 5S TMSI REALLOCATION COMPLETE 0 5 TMSI RELEASE CHANNEL RELEASE S CLEAR COMMAND T3240 T3240 ACKNOWLEDGE 10s 10s TNT 3 RELEASE COMPLETE CLEAR COMPLETE RELEASE COMPLETE (5S) CHANNEL RELEASE RELEASED DEACTIVATE SDCCH T3111 DISC UA RELEASE INDICATION RELEASE COMPLETE RELEASE RF CHANNEL RF CHANNEL RELEASE ACK. S.Smith Dec ‘94 Air Interface A-bis A-Interface

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