3.11 Multilateration Timing Advance

3GPP44.018GSM/EDGE Radio Resource Control (RRC) protocolMobile radio interface Layer 3 specificationRelease 16TS

3.11.1 General

Multilateration Timing Advance (MTA) is an optional MS feature whereby a MS attempts system access in multiple cells to allow the network to acquire information applicable for estimating the position of the MS (see 3GPP TS 43.059 and 3GPP TS 44.031). The MTA_BITMAP parameter sent in SI13 (see sub-clause 10.5.2.37b) and EC SI 2 (see sub-clause 9.1.43q) indicates if the Multilateration Timing Advance procedure is supported in a cell.

– A MS performs the radio access part of the MTA procedure using a set of autonomously selected cells which may include one or more cells for which it receives corresponding assistance information in the RRLP Multilateration Timing Advance Request message it receives from the SMLC (see 3GPP TS 44.031).

Assistance information may provide information for multiple sets of cells. When multiple cells are identified for any given set then each cell in that set shall be viewed as being co-sited and the MS shall therefore use at most use one cell from that set when performing the radio access part of the MTA procedure.

– A MS that supports the Multilateration Timing Advance feature shall support one or more of the RLC Data Block method (see sub-clause 3.11.2), Access Burst method (see sub-clause 3.11.3) and Extended Access Burst method (3.11.4) for performing the radio access part of the MTA procedure.

– If the information required to perform the radio access part of a MTA procedure in a cell selected by the MS is not provided by the assistance information but can be acquired by reading SI 13 (if PEO is enabled) or EC SI 2 information (if EC-GSM is enabled) then the MS shall read the necessary system information prior to performing the radio access part of the MTA procedure therein. Otherwise, it shall perform the radio access part of the MTA procedure in that cell using the RLC Data Block method if supported by both the MS and the selected cell.

– If the MS does not support the MTA method indicated by the RRLP Multilateration Timing Advance Request message it shall use the RLC Data Block method if both the MS and the selected cells support the RLC Data Block method.

3.11.2 RLC Data Block Method

Upon selecting a cell in which to perform the radio access part of a MTA procedure a MS shall use the RLC Data Block method therein if the corresponding RRLP Multilateration Timing Advance Request message (see 3GPP TS 44.031) indicates it is to use the RLC Data Block method and both the MS and cell support that method.

– If PEO is enabled a MS performs the radio access part of the MTA procedure using this method by sending an EGPRS MULTILATERATION REQUEST on the RACH indicating ‘RLC Data Block method’ (see sub-clause 3.5.2.1.2), is assigned an uplink EGPRS TBF and sends a single MCS-1 coded RLC data block thereon.

– If EC operation is enabled a MS performs the radio access part of the MTA procedure using this method by sending an EC MULTILATERATION REQUEST message on the EC-RACH indicating ‘RLC Data Block method’ (see sub-clause 3.5.2.1.2a), is assigned an uplink EC TBF and sends a single MCS-1 coded RLC data block thereon.

– In both cases the "TLLI", "Cell Identity", "Routing Area Identification", "MS Sync Accuracy", "MS Transmission Offset" and "Random ID" parameters are conveyed from the MS to the BSS (see 3GPP TS 44.060 [76]).

3.11.3 Access Burst Method

Upon selecting a cell in which to perform the radio access part of a MTA procedure a MS shall use the Access Burst method therein if the corresponding RRLP Multilateration Timing Advance Request message (see 3GPP TS 44.031) indicates it is to use the Access Burst method and both the MS and cell support that method.

– If EC operation is enabled a MS performs the radio access part of the MTA procedure using this method by sending an EC MULTILATERATION REQUEST message on the EC-RACH indicating ‘Access Burst method’ (see sub-clause 9.1.65).

3.11.4 Extended Access Burst Method

Upon selecting a cell in which to perform the radio access part of a MTA procedure a MS shall use the Extended Access Burst method therein if the corresponding RRLP Multilateration Timing Advance Request message (see 3GPP TS 44.031) indicates it is to use the Extended Access Burst method and both the MS and cell support that method.

– If PEO is enabled a MS performs the radio access part of the MTA procedure using this method by sending two instances of an EGPRS MULTILATERATION REQUEST message on the RACH indicating ‘Extended Access Burst method’ (see 3GPP TS 44.060 [76]).

– If EC operation is enabled a MS performs the radio access part of the MTA procedure using this method by sending two instances of an EC MULTILATERATION REQUEST message on the EC-RACH indicating ‘Extended Access Burst method’ (see sub-clause 3.5.2.1.2a and sub-clause 9.1.65).

– In both cases the "MS Transmission Offset", "MS Sync Accuracy", "Random ID" and "Short BSS ID" parameters are conveyed from the MS to the BSS (see sub-clause 9.1.65 and 3GPP TS 44.060 [76]).

3.11.5 BSS Support of Multilateration Timing Advance

If a MS performs the radio access part of the MTA procedure using the RLC Data Block method and the corresponding BSS determines it has not triggered the MTA procedure (i.e. it has not sent the SMLC a request for a location estimate for the MS, see 3GPP TS 49.031) the BSS sends the estimated "Timing Advance Value", "Cell Identity" of the cell for which the Timing Advance value was estimated, the "BTS Reception Accuracy Level" applicable to the BTS that derived the Timing Advance value, the extracted "TLLI", the extracted "Cell Identity", the extracted "Routing Area Identification" and the extracted "MS Sync Accuracy" to the MSC (see 3GPP TS 48.008).

If a MS performs the radio access part of the MTA procedure using the Extended Access Burst method and the corresponding BSS determines it has not triggered the MTA procedure the BSS sends the estimated "Timing Advance Value", "Cell Identity" of the cell for which the Timing Advance value was estimated, the "BTS Reception Accuracy Level" applicable to the BTS that derived the Timing Advance value, the extracted "Random ID", the extracted "Short BSS ID" and the extracted "MS Sync Accuracy" to the MSC (see 3GPP TS 48.008).

If a MS performs the radio access part of the MTA procedure using the RLC Data Block method or the Extended Access Burst method and the corresponding BSS determines it has triggered the MTA procedure (i.e. it sent the SMLC a request for a location estimate corresponding to the extracted "TLLI" or "Random ID", see 3GPP TS 49.031) the BSS sends its default SMLC the estimated "Timing Advance Value", the "Cell Identity" of the cell for which the Timing Advance value was estimated, the "BTS Reception Accuracy Level" applicable to the BTS that derived the Timing Advance value and the extracted "MS Sync Accuracy". Note that the "Timing Advance Value" is adjusted according to the "MS Transmission Offset" parameter extracted from the RLC Data Block or extracted from the first of two EGPRS MULTILATERATION REQUEST messages sent when PEO is enabled or extracted from the first of two EC MULTILATERATION REQUEST messages sent when EC operation is enabled (see 3GPP TS 44.060 [76], see sub-clause 9.1.65 and see 3GPP TS 45.010).

If a MS performs the radio access part of the MTA procedure using the Access Burst method and the corresponding BSS determines it triggered the MTA procedure it sends its default SMLC the estimated "Timing Advance Value", the "Cell Identity" of the cell for which the Timing Advance value was estimated and the "BTS Reception Accuracy Level" applicable to the BTS that derived the Timing Advance value.

When sending a EGPRS MULTILATERATION REQUEST message or EC MULTILATERATION REQUEST message the MS uses the Final MTA Access field (see sub-clause 9.1.65 and 3GPP TS 44.060 [76]) to indicate whether or not it is in the last cell it will use to perform the radio access part of the MTA procedure. If it indicates it is in the last cell it will use to perform the radio access part of the MTA procedure then upon completion of the radio access part of the MTA procedure in that cell it stops the MPM timer and terminates the MTA procedure. Upon receiving an EGPRS MULTILATERATION REQUEST message or EC MULTILATERATION REQUEST message indicating the MS is in the last cell it will use to perform the radio access part of the MTA procedure the BSS shall complete the MTA procedure for the MS in the current cell, inform the SMLC that no additional timing advance information is pending for the current MTA procedure (see 3GPP TS 49.031), stop the corresponding MPM timer and terminate the MTA procedure. In addition, upon receiving an uplink LLC PDU and determining that a MPM timer is running for the corresponding MS, the BSS shall inform the SMLC that no additional timing advance information is pending for the current MTA procedure, stop the corresponding MPM timer and terminate the MTA procedure.