7.8 Common Procedures to Support Access to an LMU

03.713GPPFunctional descriptionLocation Services (LCS)Release 1999Stage 2TS

The procedures in this section support the transfer of positioning related information and O&M data between an SMLC and a particular LMU associated with the SMLC.

7.8.1 Information Transfer between an NSS based SMLC and a Type A LMU

7.8.1.1 Information Transfer using an SDCCH

Figure 38: Information Transfer between an NSS based SMLC and a Type A LMU using an SDCCH

1) If there is no SCCP connection yet for an LMU between the SMLC and the MSC serving the LMU, the SMLC sends a BSSMAP-LE LMU connection request message to the MSC contained in an SCCP Connection Request. The BSSMAP-LE message shall contain the IMSI of the LMU and shall indicate whether authentication of the LMU is needed and/or ciphering.

2) For an LMU that has no main signaling link to the MSC (e.g. LMU uses a temporary SDCCH), the serving MSC performs paging to assign an SDCCH. The Channel Request message requesting an SDCCH that is sent by the LMU in response to the Paging Request shall contain an LMU establishment cause. The MSC/VLR also performs authentication and/or ciphering if requested by the SMLC.

3) The serving MSC returns a BSSMAP-LE LMU Connection Accept to the SMLC. If the paging or authentication in step 2 failed, the MSC returns a BSSMAP-LE LMU Connection Reject message.

4) If the SMLC needs to send data to the LMU, it may send one or more DTAP-LE REGISTER, FACILITY and RELEASE COMPLETE messages to the serving MSC using the SCCP connection established in steps 1 to 3. Each DTAP-LE message may carry an embedded LLP message and an indication of whether release of the SDCCH by the LMU is forbidden.

5) The serving MSC passes each DTAP-LE message received from the SMLC in step 4 to the LMU.

6) The SMLC may initiate release of the SDCCH to the LMU and the associated SCCP connection to the MSC by sending a BSSMAP-LE LMU Connection Release message.

7) For an LMU that has no other active MM and CM connections, the MSC initiates release of the SDCCH.

8) When the LMU has LCS data to send and does not currently have a signaling link, it sends an RR Channel request to the serving BTS to request an SDCCH. The RR Channel Request contains an establishment cause identifying an LMU. After assignment of the SDCCH, the LMU sends a DTAP CM Service request to the serving BSC to request an MM connection for location services.

9) The serving BSC passes the CM Service Request to the VMSC with an indication that this came from an LMU inside a Complete layer 3 Information message.

10) The serving MSC sends a BSSMAP-LE LMU Connection Request message to the SMLC associated with the LMU inside an SCCP connection request (e.g. use IMSI or LAC association to determine the SMLC). The BSSMAP-LE message shall contain the IMSI of the LMU and the address of the MSC.

11) The SMLC returns a BSSMAP-LE LMU Connection Accept. to the MSC indicating if authentication or ciphering are required.

12) The serving MSC performs authentication and ciphering if requested by the SMLC. Otherwise, a CM Service Accept is returned.

13) The LMU sends one or more DTAP-LE REGISTER, FACILITY and RELEASE COMPLETE messages to the serving MSC each containing an embedded LLP message.

14) The serving MSC passes each DTAP-LE message to the SMLC using the SCCP connection established in steps 10 to 11.

7.8.1.2 Information Transfer using a TCH

Figure 39: Information Transfer between an NSS based SMLC and a Type A LMU using a TCH

1) The SMLC or LMU establishes a signaling connection to the other entity using an SDCCH. The VMSC provides the SMLC with a called number identifying the LMU in the BSSMAP-LE LMU Connection Request or Accept

2) The SMLC sends an ISUP IAM to the VMSC with the called number from step 1 in the called party number. The IAM contains the required bearer capability and references a 64 Kbps trunk connection between the SMLC and the VMSC. The VMSC may verify that the SMLC is the source of the IAM from the SS7 link on which the IAM is received (with dedicated links on the Ls interface), the SS7 OPC in the MTP routing label or the referenced trunk connection.

3) The VMSC establishes an incoming call to the LMU with the requested bearer capability using the existing procedure defined in GSM 04.08. For this procedure, an ALERTING message from the LMU shall not be used.

4) The VMSC confirms the call establishment to the SMLC – the TCH is through connected to the 64 Kbps trunk indicated in step 2.

5) The VMSC initiates release of the SCCP connection to the SMLC established in step 1 by sending an SCCP Released message.

6) DTAP-LE REGISTER, FACILITY and RELEASE COMPLETE messages are transferred between the SMLC and LMU on the established TCH: these are transparent to the VMSC and BSC.

7) The SMLC initiates release of the TCH by sending an ISUP REL to the VMSC.

8) The SMLC acknowledges the release request.

9) The VMSC releases the call and the TCH to the LMU using the existing procedure defined in GSM 04.08.

7.8.2 Location Update Procedure between a BSS based SMLC and a Type A LMU

The following procedure supports a normal GSM location update from the perspective of a type A LMU. The location update can occur periodically, on power up, following recovery from some failure condition and when an LMU in idle mode detects that its closest BTS is in another location area. A subscription of the LMU in an HLR is not needed if this procedure is supported by the SMLC.

Figure 40: Location Update Procedure between a BSS based SMLC and a Type A LMU

1) If the LMU does not currently have a signaling link, it sends an RR Channel Request to the serving BTS to request an SDCCH. The RR Channel Request contains an establishment cause identifying an LMU. After assignment of the SDCCH, the LMU sends a DTAP Location Updating request to the BSC. This shall indicate that a follow on request is pending if the LMU has more data to send.

2) Because the BSC serving the LMU is associated with a BSS based SMLC and the Channel Request message contained an LMU establishment cause, the BSC forwards the Location Updating request to the SMLC rather than MSC. If there was previously no SDCCH, this is sent inside a BSSMAP Complete Layer 3 Information message that is contained in an SCCP Connection Request.

3) The SMLC performs existing GSM authentication and ciphering if needed for the LMU. The SMLC shall not assign a TMSI to the LMU to avoid duplicating a TMSI assigned to a normal MS by a VLR.

4) The SMLC returns a DTAP Location Updating Accept to the BSC. Unless the LMU indicated a follow on request, the SMLC may then initiate release of the SDCCH.

5) The BSC forwards the DTAP message to the LMU.

7.8.3 IMSI Detach Procedure between a BSS based SMLC and a Type A LMU

The following procedure supports a normal GSM IMSI Detach from the perspective of a type A LMU. This may be instigated if the LMU is to be deactivated – e.g. for offline maintenance.

Figure 41: IMSI Detach Procedure between a BSS based SMLC and a Type A LMU

1) If the LMU does not currently have a signaling link, it sends an RR Channel Request to the serving BTS to request an SDCCH. The RR Channel Request contains an establishment cause identifying an LMU. After assignment of the SDCCH, the LMU sends a DTAP IMSI Detach Indication to the BSC.

2) Because the BSC serving the LMU is associated with a BSS based SMLC and the Channel Request message contained an LMU establishment cause, the BSC forwards the IMSI Detach Indication to the SMLC rather than MSC. If there was previously no SDCCH, this is sent inside a BSSMAP Complete Layer 3 Information message that is contained in an SCCP Connection Request. The SMLC marks the LMU as temporarily inactive and initiates release of the SDCCH.

7.8.4 LCS Information Transfer between a BSS based SMLC and a Type A LMU

7.8.4.1 Information Transfer using an SDCCH

The following procedure supports information transfer between a BSS based SMLC and a type A LMU.

Figure 42: Information Transfer between a BSS based SMLC and a Type A LMU

1) If there is no signaling link yet for an LMU between the SMLC and the BSC serving the LMU, the SMLC sends a BSSMAP Paging message to the serving BSC inside an SCCP Unitdata message.

2) The serving BSC broadcasts an RR Paging Request.

3) The LMU sends a Channel Request message containing an LMU establishment cause to request an SDCCH. After assignment of the SDCCH, the LMU returns an RR Paging Response.

4) Because the BSC serving the LMU is associated with a BSS based SMLC and the Channel Request message in step 3 contained an LMU establishment cause, the BSC transfers the Paging Response to the SMLC, rather than MSC, in a BSSMAP Complete Layer 3 Information message contained in an SCCP Connection Request.

5) The SMLC performs normal GSM authentication and ciphering if this is needed for the LMU. The SMLC shall not assign a TMSI to the LMU to avoid duplicating a TMSI assigned to a normal MS by a VLR.

6) If the SMLC needs to send data to the LMU, it may send one or more DTAP-LE REGISTER, FACILITY or RELEASE COMPLETE messages to the BSC. Each DTAP-LE message contains an embedded LLP message and an indication of whether release of the SDCCH by the LMU is forbidden. Each DTAP-LE message is transferred by the BSC to the LMU.

7) The SMLC may initiate release of the SDCCH to the LMU by sending a BSSMAP Clear Command to the BSC.

8) The BSC returns a BSSMAP Clear Complete.

9) The BSC orders release of the SDCCH by sending an RR Channel Release to the LMU.

10) The SMLC releases the SCCP connection to the BSC by sending an SCCP Released message.

11) When the LMU has LCS data to send and does not currently have a signaling link, it sends an RR Channel Request to the serving BTS to request an SDCCH. The RR Channel Request contains an establishment cause identifying an LMU. After assignment of the SDCCH, the LMU sends a DTAP CM Service request to the serving BSC.

12) Because the BSC serving the LMU is associated with a BSS based SMLC and the Channel Request message contained an LMU establishment cause, the BSC forwards the CM Service Request with an indication that this came from an LMU to the SMLC, rather than MSC, inside a BSSMAP Complete Layer 3 Information message that is contained in an SCCP Connection Request.

13) The SMLC performs authentication and ciphering if needed for the LMU. Otherwise, a CM Service Accept is returned. The SMLC shall not assign a TMSI to the LMU to avoid duplicating a TMSI assigned to a normal MS by a VLR.

14) The LMU sends one or more DTAP-LE REGISTER, FACILITY or RELEASE COMPLETE messages to the serving BSC each containing an embedded LLP message. The BSC forwards each DTAP-LE message to the SMLC.

7.8.4.2 Information Transfer using a TCH

Figure 43: Information Transfer between a BSS based SMLC and a Type A LMU using a TCH

1) The SMLC establishes a signaling connection to the LMU using an SDCCH.

2) The SMLC sends a DTAP Setup to the LMU with the requested bearer capability.

3) The LMU returns a DTAP Call Confirmed.

4) The SMLC initiates traffic channel assignment by sending a BSSMAP Assignment Request to the BSC.

5) The BSC requests channel activation in the BTS and then sends an RR Assignment Command to the LMU.

6) The LMU acknowledges TCH assignment.

7) The BSC confirms TCH assignment.

8) The LMU confirms call establishment.

9) The SMLC acknowledges the LMU confirm.

10) DTAP-LE Connection Oriented Information messages are transferred between the SMLC and LMU on the established TCH: these are transparent to the BSC.

11) The SMLC initiates release of the TCH by sending a DTAP Disconnect to the LMU

12) The LMU returns a DTAP Release.

13) The SMLC sends a DTAP Release Complete.

14) The SMLC initiates release of the TCH by sending a BSSMAP Clear Command to the BSC.

15) The BSC returns a BSSMAP Clear Complete.

16) The BSC orders release of the TCH by sending an RR Channel Release to the LMU.

17) The SMLC releases the SCCP connection to the BSC by sending an SCCP Released message.

7.8.5 Information Transfer between an NSS based SMLC and a Type B LMU

An NSS based SMLC uses the procedure shown in Figure 44 in order to exchange LCS information with a type B LMU.

Figure 44: Information Transfer between an NSS based SMLC and a Type B LMU

1) The SMLC passes a BSSMAP-LE Connectionless Information message to the VMSC containing an embedded LLP message and the LAC/CI cell address identifying the LMU. The BSSMAP-LE message is transferred inside an SCCP Unitdata message.

2) The VMSC forwards the BSSMAP-LE message to the BSC serving the LAC/CI address.

3) The BSC transfers the embedded RRLP message to either the BTS associated with the LMU or the LMU itself inside an 08.58 LCS Information message. The BTS or LMU is identified using the LAC/CI received in step 2.

4) When the LMU has positioning information to return to the SMLC, either it or its associated BTS transfers this to the BSC inside an 08.58 LCS Information message.

5) The serving BSC forwards the RRLP message to the VMSC inside a BSSMAP-LE Connectionless Information message contained in an SCCP Unitdata message. The BSSMAP-LE message contains the LAC/CI address identifying the LMU.

6) The VMSC forwards the BSSMAP-LE message to the SMLC in an SCCP Unitdata message.

7.8.6 Information Transfer between a BSS based SMLC and a Type B LMU

A BSS based SMLC uses the procedure shown in Figure 45 in order to exchange LCS information with a type B LMU.

Figure 45: Information Transfer between a BSS based SMLC and a Type B LMU

1) The SMLC passes a BSSMAP-LE Connectionless Information message to the BSC containing an embedded LLP message and the LAC/CI cell address identifying the LMU. The BSSMAP-LE message is transferred inside an SCCP Unitdata message.

2) The BSC transfers the embedded LLP message to either the BTS associated with the LMU or the LMU itself inside an 08.58 LCS Information message. The BTS or LMU is identified using the LAC/CI received in step 1.

3) When the LMU has positioning information to return to the SMLC, either it or its associated BTS transfers this to the BSC inside an 08.58 LCS Information message.

4) The serving BSC forwards the LLP message to the SMLC inside a BSSMAP-LE Connectionless Information message contained in an SCCP Unitdata message. The BSSMAP-LE message contains the LAC/CI address identifying the LMU.