A.2 Measure Position Request

04.313GPPLocation Services (LCS)Mobile Station (MS) - Serving Mobile Location Centre (SMLC) Radio Resource LCS Protocol (RRLP)TS

A.2.1 General

The Measure Position Request is a RRLP component from the SMLC to the MS. This component is common to both E-OTD and GPS location methods. As a response to this component, the MS performs E-OTD or GPS measurements and possibly calculates its own position, if the MS and/or the network support these options. It contains the following elements.

Table A.1: Measure Position Request component content

Element

Type/Reference

Presence

Positioning Instructions

Positioning Instructions 2.2.1

M

E-OTD Reference BTS for Assistance Data

E-OTD Reference BTS for Assistance Data 2.2.2

O

E-OTD Measurement Assistance Data

E-OTD Measurement Assistance Data 2.2.3

O

E-OTD Measurement Assistance Data for System Information List

E-OTD Measurement Assistance Data for System Information List 2.2.4

O

GPS Assistance Data

GPS Assistance Data 4.2.4

O

GPS Time Assistance Measurement Request

GPS Time Assistance Measurement Request 2.2.4a

O

GPS Reference Time Uncertainty

GPS Reference Time Uncertainty 2.2.4b

O

A.2.2 Elements

A.2.2.1 Positioning Instructions Element

The purpose of Positioning Instructions element is to express the allowed/required location method(s), and to provide information required QoS. This element is mandatory in the Measure Position Request message, and contains the following fields:

Method Type

This field indicates whether MS based or assisted version is allowed/requested. If the Methods field includes more than one method, the Method Type applies to all of them. This field is mandatory, and has the following values:

‘0’: MS assisted

‘1’: MS based

‘2’: MS based is preferred, but MS assisted is allowed

‘3’: MS assisted is preferred, but MS based is allowed

Positioning Methods

This field indicates which location method or methods should be used. This field is mandatory.

‘0’: E-OTD

‘1’: GPS

‘2’: E-OTD or GPS (i.e. both can be reported)

Response Time

This field indicates the desired response time. However, when performing measurements, the desired response time may be exceeded. This field is mandatory.

The response time is 2N seconds, where N is the value in this field. Thus the desired maximum response time can be 1, 2, 4, 8, 16, 32, 64, or 128 seconds.

Range: 0-7

Accuracy

This field indicates the required accuracy of the location estimate. This is field is mandatory when Method Type is ‘1’, ‘2’, or ‘3’ and optional when Method Type is ‘0’.

This field is 7 bit Uncertainty Code as defined in 3GPP TS 03.32.

Multiple Sets

This field indicates whether MS is requested to send multiple E-OTD/GPS Measurement Information Sets. The maximum number of measurement sets is three. This is field is mandatory. MS is expected to include the current measurement set. Additionally MS may include historical measurement sets, or measure new additional sets if the response time allows that:

‘0’: multiple IEs can be send

‘1’: sending of multiple sets is not allowed

Environment Characterization

Environment Characterization field provides the MS with information about expected multipath and NLOS in the current area. This field is optional.

‘0’: possibly heavy multipath and NLOS conditions (e.g. bad urban or urban)

‘1’: no or light multipath and usually LOS conditions (e.g. suburban or rural)

‘2’: not defined or mixed environment

‘3’: reserved for future use

A.2.2.2 E-OTD Reference BTS for Assistance Data Element

The RTD and 51 multiframe offset values in the E-OTD Measurement Assistance Data element and the E-OTD Measurement Assistance Data for System Information List element are calculated relative to the BTS indicated in this element. Also the E-OTD Measurement Assistance data for System Information List element, if present, refers to the System Information Neighbor List of this reference BTS.

Inclusion of this parameter is mandatory for E-OTD since it is not possible to reliably default to the current serving BTS for the target MS, as there is a small chance that the SMLC does not know this. If the E-OTD Measurement Assistance data for System Information List element is present, the current serving cell must be the same as reference BTS identified in this element.

BCCH Carrier

This field indicates the absolute RF channel number of BCCH of the reference BTS. This field is mandatory.

Range: 0 – 1023

BSIC

This field indicates the BSIC (Base Station Identity Code) of the reference BTS. This field is mandatory.

Range: 0 – 63

Time Slot Scheme

The Time Slot Scheme field indicates the type of transmission scheme the reference BTS is using. If the MS measures BTSs signals from time slots other than 0 or 4, and it is informed about the burst length schemes used by BTSs, then it can compensate for the possible error. (This is necessary if the MS averages bursts from different time slots, and the BTS uses varying lengths of bursts.) This field is mandatory.

‘0’ = all time slots are 156.25 bits long

‘1’ = time slots 0 and 4 are 157 bits long and other time slots are 156 bits long

BTS Position

This field contains the BTS position in the format defined in 3GPP TS 03.32. This field is optional, but should be present for MS based E-OTD positioning. The allowed shapes are:

– ellipsoid point;

– ellipsoid point with altitude and uncertainty ellipsoid.

A.2.2.3 E-OTD Measurement Assistance Data Element

This element identifies BTSs that are used for E-OTD measurements. This element helps the MS to make measurements from neighbor BTS (even below decoding level). This element is optional in the Measure Position Request component. The presence of this element means that the MS should try to measure the E-OTD values between the reference BTS and the BTSs identified in this element.

This element is used to deliver E-OTD measurement assistance data for those BTSs, that are not included in the System Information Neighbor List of the reference BTS, if necessary.

The RTD and 51 multiframe offset values are calculated relative to the BTS indicated in the E-OTD Reference BTS for Assistance Data element. This element contains the following fields.

Number of BTSs

This field indicates how many BTSs are included in this IE. This field is mandatory. The maximum number of BTSs in this message for whom the assistance data can be given is 16 (reference BTS and 15 neigbour BTSs). Thus the sum of Number of BTSs field in this IE and total amount of E-OTD Neighbor present bits with value ‘1’ in E-OTD Measurement Assistance Data for System Information List IE can be at a maximum 15.

Range: 1 to 15.

The following fields are repeated for the number of BTSs included in the Number of BTSs field.

BCCH Carrier

This field indicates the absolute RF channel number of BCCH of the particular BTS. This field is mandatory.

Range: 0 – 1023

BSIC

This field indicates the BSIC (Base Station Identity Code) of the particular BTS. This field is mandatory.

Range: 0 – 63

Multiframe Offset

This field indicates the frame difference between the start of the 51 multiframes frames being transmitted from this BTS and the reference BTS. The multiframe offset is defined as TBTS – TRef, where TBTS is the time of the start of the 51 multiframe in the BTS in question, and TRef is the time of the start of the 51 multiframe in the reference BTS. This field is mandatory. Multiframe Offset may be used to calculate the Expected Multiframe Offset (the Multiframe Offset value that MS is expected to measure between this BTS and reference BTS in its current estimated location).

Expected Multiframe Offset = (Multiframe Offset + Adjustment) modulo 51

Adjustment = 1 if Rough RTD – Expected OTD >= 850

Adjustment = -1 if Rough RTD – Expected OTD =< -850

Adjustment = 0 if –400 =< Rough RTD – Expected OTD =< 400

If the Rough RTD – Expected OTD is not within any of the ranges above, an error has occurred and the Expected OTD should be ignored and no Expected Multiframe Offset can be calculated.

Range: 0 – 51

Usable range of Multiframe Offset value is 0 – 50. The Multiframe Offset value 51 shall not be encoded by the transmitting entity and shall be treated by the receiving entity as 0.

Time Slot Scheme

The Time Slot Scheme field indicates the type of transmission scheme the particular BTS is using. If the MS measures BTSs signals from time slots other than 0 or 4, and it is informed about the burst length schemes used by BTSs, then it can compensate for the possible error. (This is necessary if the MS averages bursts from different time slots, and the BTS uses varying lengths of bursts.) This field is mandatory.

‘0’ = all time slots are 156.25 bits long

‘1’ = time slots 0 and 4 are 157 bits long and other time slots are 156 bits long

Rough RTD

This field indicates the rough RTD value between this BTS and reference BTS. The used resolution is 1 bits. This RTD value is the RTD value of TS0s (i.e. the difference in starting of TS0), not only the RTD between starts of bursts. The RTD is defined as TBTS – TRef, where TBTS is the time of the start of TS0 in the BTS in question, and TRef is the time of the start of the TS0 in the reference BTS. This field is mandatory.

Range: 0 – 1250

Usable range of Rough RTD value is 0 – 1249. The Rough RTD value 1250 shall not be encoded by the transmitting entity and shall be treated by the receiving entity as 0.

Accurate RTD values are needed for MS based E-OTD, i.e. when the MS calculates its own position.

Expected OTD

This field indicates the OTD value that MS is expected to measure between this BTS and reference BTS in its current estimated location. SMLC can estimate MS’s location roughly e.g. based on serving BTS coordinates, TA, and possibly some other information. The used resolution is 1 bits. This OTD value is the OTD value of TS0s (i.e. the difference in starting of TS0), not only the OTD between starts of bursts. The OTD is defined as TBTS – TRef, where TBTS is the time of the start of TS0 in the BTS in question, and TRef is the time of the start of the TS0 in the reference BTS. This is element is Release 98 extension and it is an optional element included in Release98-Ext IE. SMLC shall send this element to MS supporting MS Assisted or MS Based E-OTD.

Range: 0 – 1250

Usable range of Expected OTD value is 0 – 1249. The Expected OTD value 1250 shall not be encoded by the transmitting entity and shall be treated by the receiving entity as 0.

Uncertainty Of Expected OTD

This field indicates the uncertainty in Expected OTD value. The uncertainty is related to SMLC’s estimation of MS’s location. The uncertainty defines following search window for MS, that it can use to speed up the OTD measurements:

Expected OTD – Uncertainty < measured OTD < Expected OTD + Uncertainty.

This is element is Release 98 extension and it is an optional element included in Release98-Ext IE. SMLC shall send this element to MS supporting MS Assisted or MS Based E-OTD.

Range is 0 – 7 with following encoding:

‘0’ 0 < uncertainty <= 2 bit

‘1’ 2 < uncertainty <= 4 bit

‘2’ 4 < uncertainty <= 8 bit

‘3’ 8 < uncertainty <= 12 bit

‘4’ 12 < uncertainty <= 16 bit

‘5’ 16 < uncertainty <= 22 bit

‘6’ 22 < uncertainty <= 30 bit

‘7’ uncertainty > 30 bit.

NOTE: If uncertainty in MS’s location is x bits, uncertainty in Expected OTD is 2*x (in the worst case). When the uncertainty is given with value ‘7’ no upper bound exist for the uncertainty.

The following fields tell the coordinates of neighbor BTSs that are used for E-OTD measurements, and also fine RTD values. This information allows the MS to calculate its own location. These fields (Fine RTD, Relative north, Relative east and Relative altitude) are optional. All of Fine RTD, Relative north, and Relative east fields must be present, if some of them is included.

Fine RTD

This field indicates the fine RTD value between this BTS and reference BTS. It provides the 1/256 bit duration resolution to the value expressed in the corresponding Rough RTD field. This RTD value is the RTD value of TS0s (i.e. the difference in starting of TS0), not only the RTD between starts of bursts. The RTD is defined as TBTS – TRef, where TBTS is the time of the start of TS0 in the BTS in question, and TRef is the time of the start of the TS0 in the reference BTS. This field is optional.

Range: 0 – 255

Relative North

This field indicates the distance of the neighbor BTS from the reference BTS in north- (negative values mean south) direction. This field is optional. The units are 0.03 seconds. The used reference ellipsoid is WGS 84 ellipsoid.

Range: -200000…200000

Relative East

This field indicates the distance of the neighbor BTS from the reference BTS in east (negative values mean west) direction. This field is optional. The units are 0.03 seconds. The used reference ellipsoid is WGS 84 ellipsoid.

Range: -200000 … 200000

Relative Altitude

This field indicates the altitude of the neighbor BTS relative to the reference BTS in meters. This field is optional.

Range: -4000 .. 4000 meters

A.2.2.4a GPS Time Assistance Measurement Request Element

This component does not have any information contents. If this component is present, the MS is requested to return GPS time assistance measurements..

A.2.2.4b GPS Reference Time Uncertainty Element

This element provides the accuracy of the relation GPS and GSM time in the Reference Time field in GPS Assistance Data IE. If GPS TOW is the given GPS time, then the true GPS time, corresponding to the provided GSM time as observed at the MS location, lies in the interval (GPS TOW – GPS Reference Time Uncertainty, GPS TOW + GPS Reference Time Uncertainty). An entity that supports this element shall always include it when appropriate. This means that when the element is expected but is not received, lack of support at the sender can be assumed and some implementation dependent default interpretation can then be applied.

The uncertainty r, expressed in microseconds, is mapped to a number K, with the following formula:

r = C*(((1+x)K)-1)

with C = 0.0022 and x = 0.18. With 0 £ K £ 127, a suitably useful range between 0 and 3 second is achieved for the uncertainty, while still being able to code down to values as small as 0.3 nanoseconds. To encode any higher value of uncertainty than that corresponding in the above formula to K=127, the same value, K=127, shall also be used. The uncertainty is then coded on 7 bits, as the binary encoding of K.

Table A.1a: Example values for the GPS Reference Time Uncertainty Parameter Format

Value of K

Value of uncertainty

0

0 nanoseconds

1

0.396 nanoseconds

2

0.863 nanoseconds

50

8.64 microseconds

127

≥ 2.96 seconds

A.2.2.4 E-OTD Measurement Assistance Data for System Information List Element

This element identifies those BTSs in the System Information Neighbor List that are used for E-OTD measurements. The System Information Neighbor Lists, to which this assistance data is given, are System Information Neighbor Lists that are send in the dedicated mode. This element helps the MS to make measurements from those neighbor BTS (even below decoding level). This element is optional in the Measure Position Request component. The presence of this element means that the MS should use the BTSs identified here to the E-OTD measurements.

The RTD and 51 multiframe offset values are calculated relative to the reference BTS. This element contains the following fields.

Number of Neighbors

This field indicates how many neighbors are included in this IE.

Range: 1-32

The following fields are repeated for the number indicated in the Number of Neighbors field.

E-OTD Neighbor present

This field indicates whether the information concerning a certain BTS in the Neighbor List is present. Altogether no more than 15 BTS can have the indication "Neighbor is included". The maximum number of BTSs in this message for whom the assistance data can be given is 16 (reference BTS and 15 neigbour BTSs). Thus the sum of total amount of E-OTD Neighbor present bits with value ‘1’ in this IE and Number of BTSs field in E-OTD Measurement Assistance Data IE can be at a maximum 15.

‘0’ Neighbor not included

‘1’ Neighbor is included

The following fields (BSIC, Multiframe Offset, Time Slot Sscheme and Rough RTD) are included if E-OTD neighbor present field is set to ‘1’.

BSIC

This field indicates the BSIC (Base Station Identity Code) of the particular BTS. This field is mandatory.

Range: 0 – 63

Multiframe Offset

This field indicates the frame difference between the start of the 51 multiframes frames being transmitted from this BTS and the reference BTS. The multiframe offset is defined as TBTS – TRef, where TBTS is the time of the start of the 51 multiframe in the BTS in question, and TRef is the time of the start of the 51 multiframe in the reference BTS. This field is mandatory. Multiframe Offset may be used to calculate the Expected Multiframe Offset (the Multiframe Offset value that MS is expected to measure between this BTS and reference BTS in its current estimated location).

Expected Multiframe Offset = (Multiframe Offset + Adjustment) modulo 51

Adjustment = 1 if Rough RTD – Expected OTD >= 850

Adjustment = -1 if Rough RTD – Expected OTD =< -850

Adjustment = 0 if –400 =< Rough RTD – Expected OTD =< 400

If the Rough RTD – Expected OTD is not within any of the ranges above, an error has occurred and the Expected OTD should be ignored and no Expected Multiframe Offset can be calculated.

Range: 0 – 51

Usable range of Multiframe Offset value is 0 – 50. The Multiframe Offset value 51 shall not be encoded by the transmitting entity and shall be treated by the receiving entity as 0.

Time Slot Scheme

The Time Slot Scheme field indicates the type of transmission scheme the particular BTS is using. If the MS measures BTSs signals from time slots other than 0 or 4, and it is informed about the burst length schemes used by BTSs, then it can compensate for the possible error. (This is necessary if the MS averages bursts from different time slots, and the BTS uses varying lengths of bursts.) This field is mandatory.

‘0’ = all time slots are 156.25 bits long

‘1’ = time slots 0 and 4 are 157 bits long and other time slots are 156 bits long

Rough RTD

This field indicates the RTD value between this BTS and the reference BTS. The used resolution is 1 bit. This RTD value is the RTD value of TS0s (i.e. the difference in starting of TS0), not only the RTD between starts of bursts. The RTD is defined as TBTS – TRef, where TBTS is the time of the start of TS0 in the BTS in question, and TRef is the time of the start of the TS0 in the reference BTS. This field is mandatory.

Range: 0 – 1250

Usable range of Rough RTD value is 0 – 1249. The RoughRTD value 1250 shall not be encoded by the transmitting entity and shall be treated by the receiving entity as 0.

Expected OTD

This field indicates the OTD value that MS is expected to measure between this BTS and reference BTS in its current estimated location. SMLC can estimate MS’s location roughly e.g. based on serving BTS coordinates, TA, and possibly some other information. The used resolution is 1 bits. This OTD value is the OTD value of TS0s (i.e. the difference in starting of TS0), not only the OTD between starts of bursts. The OTD is defined as TBTS – TRef, where TBTS is the time of the start of TS0 in the BTS in question, and TRef is the time of the start of the TS0 in the reference BTS. This is element is Release 98 extension and it is an optional element included in Release98-Ext IE. SMLC shall send this element to MS supporting MS Assisted or MS Based E-OTD.

Range: 0 – 1250

Usable range of Expected OTD value is 0 – 1249. The Expected OTD value 1250 shall not be encoded by the transmitting entity and shall be treated by the receiving entity as 0.

Uncertainty Of Expected OTD

This field indicates the uncertainty in Expected OTD value. The uncertainty is related to SMLC’s estimation of MS’s location. The uncertainty defines following search window for MS, that it can use to speed up the OTD measurements:

Expected OTD – Uncertainty < measured OTD < Expected OTD + Uncertainty.

This is element is Release 98 extension and it is an optional element included in Release98-Ext IE. SMLC shall send this element to MS supporting MS Assisted or MS Based E-OTD.

Range is 0 – 7 with following encoding:

‘0’ 0 < uncertainty <= 2 bit

‘1’ 2 < uncertainty <= 4 bit

‘2’ 4 < uncertainty <= 8 bit

‘3’ 8 < uncertainty <= 12 bit

‘4’ 12 < uncertainty <= 16 bit

‘5’ 16 < uncertainty <= 22 bit

‘6’ 22 < uncertainty <= 30 bit

‘7’ uncertainty > 30 bit.

NOTE: If uncertainty in MS’s location is x bits, uncertainty in Expected OTD is 2*x (in the worst case). When the uncertainty is given with value ‘7’ no upper bound exist for the uncertainty.

The following fields tell the coordinates of neighbor BTSs that are used for E-OTD measurements, and also fine RTD values. This information allows the MS to calculate its own location. These fields (Fine RTD, Relative north, Relative east and Relative altitude) are optional. All of Fine RTD, Relative north, and Relative east fields must be present, if some of them is included.

Fine RTD

This field indicates the fine RTD value between this BTS and reference BTS. It provides the 1/256 bit duration resolution to the value expressed in the corresponding Rough RTD field. This RTD value is the RTD value of TS0s (i.e. the difference in starting of TS0), not only the RTD between starts of bursts. The RTD is defined as TBTS – TRef, where TBTS is the time of the start of TS0 in the BTS in question, and TRef is the time of the start of the TS0 in the reference BTS. This field is optional.

Range: 0 – 255

Relative North

This field indicates the distance of the neighbor BTS from the reference BTS in north- (negative values mean south) direction. This field is optional. The units are 0.03 seconds. The used reference ellipsoid is WGS 84 ellipsoid.

Range: -200000…200000

Relative East

This field indicates the distance of the neighbor BTS from the reference BTS in east (negative values mean west) direction. This field is optional. The units are 0.03 seconds. The used reference ellipsoid is WGS 84 ellipsoid.

Range: -200000 … 200000

Relative Altitude

This field indicates the altitude of the neighbor BTS relative to the reference BTS in meters. This field is optional.

Range: -4000 .. 4000 meters