A.9 Multilateration Timing Advance Request

3GPP44.031Location Services (LCS)Mobile Station (MS) - Serving Mobile Location Centre (SMLC) Radio Resource LCS Protocol (RRLP)Release 17TS

A.9.1 General

The Multilateration Timing Advance Request is a RRLP component sent from the SMLC to the MS. The SMLC uses the minimum guaranteed assessment error value of the BTS (i.e. the BTS Reception Accuracy Capability received from the BSC as part of assistance information and MS Sync Accuracy received from SGSN in the PERFORM-LOCATION-REQUEST PDU) when determining the Target-Number-of-Cells to use in the triggering RRLP message and the BTS Reception Accuracy Level reported by that BTS (when the Multilateration Timing Advance procedure is ongoing) to estimate the MS position and the corresponding positioning accuracy (see 3GPP TS 45.010 and 3GPP TS 43.059). This RRLP component contains the following elements.

Table A.9.1: Multilateration Timing Advance Request component content

Element

Type/Reference

Presence

Target-Number-of-Cells

Target-Number-of-Cells A.9.2.1

M

Requested-MS-Synchronization-Accuracy

Requested-MS-Synchronization-Accuracy A.9.2.2

M

MTA-Method

MTA-Method A.9.2.3

M

Random-ID-Set

MTA-Method A.9.2.4

M

MPM-Timer

MPM-Timer A.9.2.5

M

Serving-Cell

Serving-Cell A.9.2.6

M

Co-Sited-Cells

Co-Sited-Cells A.9.2.7

O

Cell-Set N

Cell Set N A.9.2.8

M

MTA-Security

MTA-Security A.9.2.9

O

A.9.2 Elements

A.9.2.1 Target-Number-of-Cells Element

This field is a 3 bit integer used to indicate the optimum number of cells a MS is to use when performing the radio access part of the MTA procedure. This field is mandatory, and has the following values:

0 0 0 : 2 cells
0 0 1 : 3 cells

1 1 1 : 9 cells

A.9.2.2 Requested-MS-Synchronization-Accuracy Element

This field is a 4 bit integer used to indicate the synchronization accuracy the MS should attempt to realize when performing the radio access part of the MTA procedure using the RLC Data Block method or the Extended Access Burst method and is coded as per the value part of the MS Synchronization Accuracy IE defined in 3GPP TS 49.031 [7]. The synchronization accuracy requested by this field shall be ignored when performing the radio access part of the MTA procedure using the Access Burst method.

A.9.2.3 MTA-Method

This field indicates the MTA method the MS is to use when performing the radio access part of the MTA procedure and allows for indicating the following methods.

RLC Data Block: If this method is indicated then no additional information is included within the MTA-Method information.

Access Burst: If this method is indicated then no additional information is included within the MTA-Method information.

Extended Access Burst: If this method is indicated then the Short BSS ID field is included as part of the MTA-Method information.

These methods require that either PEO or EC-GSM-IoT operation is enabled in the MS. If EC-GSM-IoT operation is enabled but CC1 is not used on the uplink then the MS shall use the RLC Data Block method (if supported). If neither PEO or EC-GSM-IoT operation is enabled the MS shall not perform the commanded MTA procedure.

Short-BSS-ID

This parameter identifies the serving BSS within a cluster of BSS areas and is used for the Extended Access Burst method. The Short BSS ID together with a Random ID value identify the target MS for the Multilateration Timing Advance procedure in a unique way in the network.

A.9.2.4 Random-ID

This parameter is used by a MS when it performs the radio access part of the MTA procedure using the RLC Data Block or Extended Access Burst method. The Random ID value sent by a MS performing the radio access part of the MTA procedure is selected from a set of up to 9 Random ID values provided by the RRLP Multilateration Timing Advance Request message. Each Random ID value provided by the RRLP message can only be used in one cell used by a MS when performing the radio access part of the MTA procedure. After reception by the BSS it is sent to the SMLC along with corresponding MTA timing advance information using a SCCP connection that the Random ID is logically associated with (i.e. when the SMLC first allocates a set of Random ID values for inclusion in a RRLP message they will always be associated with a SCCP connection used by the SMLC for an ongoing MTA procedure). The reception of any one of the allocated Random ID values along with corresponding MTA timing advance information therefore allows the SMLC to validate the timing advance information.

A.9.2.5 MPM-Timer

This field is a 3 bit integer used to indicate the maximum amount of time the MS can use to perform the radio access part of the MTA procedure and is coded as per the MPM Timer field defined in 3GPP TS 49.031 [7].

A.9.2.6 Serving-Cell

This field is set to ‘1’ if the SMLC requests the MS to include the serving cell when performing the radio access part of the MTA procedure.

A.9.2.7 Co-Sited-Cells

This field identifies the set of cells that are co-sited with the serving cell and therefore shall not be used by the MS when performing the radio access part of the MTA procedure.

A.9.2.8 Cell-Set N

This field provides assistance information for one or more sets of cells wherein information for at least one cell is provided within each Cell Set for which assistance information is provided. When multiple cells are identified for a given Cell Set then each cell in the set is co-sited and the MS shall therefore use at most one cell from the set when performing the radio access part of the MTA procedure. If the ARFCN and BSIC of the serving cell is included for a cell within a Cell Set then the MS shall use that cell when performing the radio access part of the MTA procedure.

Short-ID

This parameter identifies the cell specific Short ID value to be sent from the MS to the BSS when the MS performs the radio access part of the MTA procedure in a cell using the Access Burst method. It is part of the MTA related measurement information passed from the BSS to the SMLC and is used by the SMLC to validate the corresponding MTA related measurement information it receives for that cell.

ARFCN
This field is the binary representation of the absolute radio frequency channel number (ARFCN) defined in 3GPP TS 45.005.

BSIC-Info

This field identifies the 9 bit BSIC (see 3GPP TS 45.003 and 3GPP TS 45.008) associated with the indicated ARFCN.

EC-Cell-Information

When a cell supports EC-GSM-IoT the corresponding EC-RACH-Control-Parameters may be included as part of the assistance information. If excluded for that cell the MS shall default to using the EC-RACH-Control-Parameters provided for any other cell in that set. If EC-RACH-Control-Parameters are not provided for any cell in a set of cells that support EC-GSM-IoT then the MS shall read the EC-BCCH for the cell in that cell set that it chooses to use to perform the Multilateration Timing Advance procedure and thereby acquire the required EC-RACH-Control-Parameters information.

PEO-Cell-Information

When a cell supports PEO the corresponding RACH-Control-Parameters may be included as part of the assistance information. If excluded for that cell the MS shall default to using the RACH-Control-Parameters provided for any other cell in that set. If RACH-Control-Parameters are not provided for any cell in a set of cells that support PEO then the MS shall read the BCCH for the cell in that cell set that it chooses to use to perform the Multilateration Timing Advance procedure and thereby acquire the required RACH-Control-Parameters information.

EC-BS-CC-CHANS

This field is a 2 bit integer and indicates the number of extended coverage common control channels (EC-CCCHs) supported in the cell (see 3GPP TS 44.018).

EC-RXLEV-ACCESS-MIN
This field is a 6 bit integer and is coded as the binary representation of the minimum received signal level at the MS for which it is permitted to access the system when using the EC-RACH, see 3GPP TS 45.008.

MS-TXPWR-MAX-CCH
This field is coded as the binary representation of the "power control level" in 3GPP TS 45.005 corresponding to the maximum TX power level an MS may use when accessing the system on the (EC-)CCCH. This value shall be used by the Mobile Station according to 3GPP TS 45.008.

LB-MS-TXPWR-MAX-CCH
The LB_MS_TXPWR_MAX_CCH field is coded as the binary representation of the "power control level" in 3GPP TS 45.005 corresponding to the maximum TX power level an MS may use on all other than DCS 1800 and PCS 1900 frequency bands when accessing the system on the (EC-)CCCH. The use of this field is defined in 3GPP TS 45.008.

CELL-SELECTION-RLA-MARGIN
The CELL_SELECTION_RLA_MARGIN field provides the MS with information whether RLA_EC and RLA_GC based measurements may be omitted or not. The use of this field is defined in 3GPP TS 45.008.

DL-CC-Selection
This field is a BOOLEAN and indicates the method for selecting the downlink coverage class to be used by the MS (see 3GPP TS 44.018). The use of this field is defined in 3GPP TS 45.008.

BT-Threshold-DL
This field is a 5 bit integer and indicates the signal level threshold below which blind physical layer transmissions are used on EC-CCCH. The use of this field is defined in 3GPP TS 45.008.

CC2-Range-DL

CC3-Range-DL
These fields are 5 bit integers and are optionally sent by the network to indicate the signal level range of the indicated downlink coverage classes. The presence of one or both of these fields indicates network support of the associated downlink coverage class. The use of these fields is defined in 3GPP TS 45.008.

BT-Threshold-UL
This field is a 5 bit integer and indicates the signal level threshold below which blind physical layer transmissions are used on EC-RACH. The use of this field is defined in 3GPP TS 45.008.

CC2-Range-UL
CC3-Range-UL

These fields are 5 bit integers and are optionally sent by the network to indicate the signal level range of the indicated uplink coverage classes. The presence of one or both of the above fields indicates network support of the associated uplink coverage class. The use of these fields is defined in 3GPP TS 45.008.

CC4-Range-UL

This field is optionally sent by the network to indicate the signal level range of uplink coverage class 4 and when included it implicitly indicates uplink class 5 is supported. The use of this field is defined in 3GPP TS 45.008.

BSPWR
This field indicates the BTS output power transmitted on FCCH and EC-SCH. The use of this field is defined in 3GPP TS 45.008.

DL-Signal-Strength-Step-Size
This field indicates the step-size in signal level above BT_Threshold_DL possible to report by the MS in the EC MULTILATERATION REQUEST message. The use of this field is defined in 3GPP TS 44.018.

EC-Reduced-PDCH-Allocation 

This field indicates that the number of consecutive PDCHs the network allocates when assigning an EC TBF to a MS indicating Coverage Class CC2, CC3 or CC4 on the uplink or downlink during packet access. The use of this field is defined in 3GPP TS 44.018.

EC-Max-Retrans
This field is a 2 bit integer and indicates the maximum number of retransmissions on EC-RACH. It is encoded as the Max retrans field in the RACH Control Parameters IE defined in 3GPP TS 44.018.

Sm
This field is a 2 bit integer used by a MS to determine the number of multiframes it needs to read on the EC-AGCH in an attempt to find a response matching its last EC-RACH transmission. The use of this field is defined in 3GPP TS 44.018.

Tm
This field is a 2 bit integer used by a MS to determine the number of multiframes on the EC-RACH from which it randomly selects a transmission/retransmission opportunity. The use of this field is defined in 3GPP TS 44.018.

Access-Timeslots
This field is a BOOLEAN and indicates whether random access mapped over two timeslots shall be applied or not (see 3GPP TS 44.018). The use of this field is defined in 3GPP TS 44.018.

ALPHA
This field is an optional 4 bit integer and provides the binary representation of the parameter  for MS output power control in units of 0.1, see 3GPP TS 45.008. For encoding and description of the ALPHA field see the Global Power Control Parameters IE in 3GPP TS 44.060.

T3168
T3192
T3226

These fields are optional 3 bit integers. The use of these fields is defined in 3GPP TS 44.060.

T3248

This field is a 2 bit integer. The use of this field is defined in 3GPP TS 44.060.

MTA-BITMAP
This field contains a 4 bit bitmap indicating the Multilateration Timing Advance methods supported by a cell. See 3GPP TS 44.018 for a description of the Multilateration Timing Advance methods. Support for each of the methods listed below is provided using a BOOLEAN.

– MTA-RLC-Data-Block-method

– MTA-Access-Burst-method

– MTA-Extended-Access-Burst-method

– MTA-spare

RXLEV-ACCESS-MIN
This field is a 6 bit integer and is coded as the binary representation of the minimum received signal level at the MS for which it is permitted to access the system when using the RACH, see 3GPP TS 45.008.

Max-Retrans
This field is a 2 bit integer and indicates the maximum number of retransmissions on RACH. The use of this field is defined in 3GPP TS 44.018.

Tx-integer
This field is a 4 bit integer and indicates the number of slots to spread the transmission on RACH. The use of this field is defined in 3GPP TS 44.018.

A.9.2.9 MTA-Security

This field indicates the method for verifying the integrity of the MTA Access procedure.

MTA Access Security: If this method is indicated the MS generates MTA Signature at the end of MTA Access procedure based on the parameters associated with the successfully completed radio access parts of the MTA procedure using the Integrity protection keys negotiated with SGSN.

BSS Duplication Detection Method: If this method is indicated, MS sends MTA sequence number in each of the MTA Access attempt including the last attempt. BSS verifies the integrity of the access procedure based on detection of duplicate sequence numbers received from the same MS identifier.