9.2c GPRS Cell Change for the PS Domain in A/Gb mode

3GPP43.059Functional stage 2 description of Location Services (LCS) in GERANRelease 17TS

9.2c.1 Intra-BSS Cell Change

The procedure shown below is used in order to keep an SMLC updated about Intra-BSS cell changes during a positioning procedure for a target MS in the PS domain in A/Gb-mode (note that unlike the CS domain and handover, the BSSLAP reset procedure is not used). The following procedure is applicable except when U-TDOA positioning is ongoing in the BSS as described in sub-clause 9.5.2.4 of this specification.

Figure 28c: Cell Change with BSSAP-LE Perform Location Information for the PS Domain

1. The MS detects a cell change and sends a cell update message or routing area update message to the SGSN (for more information, see 3GPP TS 23.060).

2. The SGSN sends a BSSGP FLUSH-LL PDU to the BSS. If the cell change is an Inter-NSE Cell Change, the NSEI of the new cell is provided.

3. The BSS acknowledges by sending a BSSGP FLUSH-LL-ACK PDU to the SGSN.

4. The BSS detects that a positioning procedure is active and the BSS is able to continue the positioning procedure in the new cell and sends a BSSAP-LE Perform Location Information message to the SMLC. This message contains the Cell Identifier for the new cell. If the Timing Advance value for the MS in the new cell is available in the BSS, it shall also be included. The BSS may send this message either if it receives the indication from the SGSN about the cell change (the BSSGP FLUSH-LL) or if it detects the cell change on its own (e.g. network controlled cell reselection).

9.2c.2 Inter-BSS Cell Change

The procedure shown below is used to abort the positioning procedure when an Inter-BSS cell change occurs for a target MS in the PS domain in A/Gb-mode. The following procedure is applicable except when U-TDOA positioning is ongoing in the BSS as described in sub-clause 9.5.2.5 of this specification.

Figure 28d: Cell Change with positioning abort for the PS Domain

1. The MS detects a cell change and sends a cell update message or routing area update message to the SGSN (for more information, see 3GPP TS 23.060).

2. The SGSN sends a BSSGP FLUSH-LL PDU to the BSS. The NSEI of the new cell is provided.

3. The BSS acknowledges by sending a BSSGP FLUSH-LL-ACK PDU to the SGSN.

4. The BSS detects that a positioning procedure is active and that the BSS is not able to continue the positioning procedure in the new cell (e.g. Inter BSS Cell Change) and sends a BSSAP-LE Perform Location Abort message to the SMLC. The IE LCS Cause indicates the reason for the abort (e.g. “Inter BSS Cell Change”). The BSS then awaits the BSSAP-LE Perform Location Response from the SMLC, which it will forward in a BSSGP Perform Location Response to the SGSN.