A.2 Messages

04.713GPPLocation Services (LCS)Mobile radio interface Layer 3 specificationRelease 1998TS

The messages below are considered to be transported between the SMLC and the LMU.

A.2.1 RIT Measurement Request Message

The RIT Measurement Request is a message from the SMLC to the LMU. As a response to it the LMU performs Real Time Difference (RTD) or Absolute Time Difference (ATD) measurements. It contains the following information elements.

Table A.1: RIT Measurement Request message content

Information element

Type/Reference

Presence

Message Type

Message Type A.2.1.1.1

M

Measurement Instructions

Measurement Instructions A.2.1.1.2

M

BTS List

BTS List A.2.1.1.3

C

A.2.1.1 RIT Measurement Request Message Information Elements

A.2.1.1.1 Message Type IE

This IE contains the type of the message. This IE is mandatory.

A.2.1.1.2 Measurement Instructions IE

The purpose of the Measurement Instructions IE is to inform the LMU about the measurement type (RTD/ATD), measurement result reporting rate, and tell which BTSs should be measured. This IE is mandatory, and it contains the following fields:

Measurement Type

This field indicates whether AT of reference BTS is required.

‘0’: AT of reference BTS should be reported. If AT of reference BTS can not be measured, no ATD/RTD measurements are reported, but RIT Error IE is sent instead.

‘1’: AT of reference BTS should be reported . If AT of reference BTS can not be measured, ATD/RTD measurements are reported anyhow.

‘2’: ATD/RTD measurements timestamped with frame number of the reference BTS should be performed.

Reporting Period Format

This field describes the units of the Reporting Period field. This field is optional. If this field is included, RIT Measurement Responses shall be send with the period indicated in this and Reporting Period fields.

‘0’: Reporting Period is told in tens of seconds.

‘1’: Reporting Period is in tens of minutes.

Reporting Period

This field describes the value for the reporting period, i.e. the required time period between the RIT Measurement Response messages. Its units and multiplication factor are defined in the Reporting Period Format field. This field is conditional and included only if the Reporting Period Format is included.

Range: 1-120

Change Limit

This field indicates the limit for the change of AT or ATD /RTD values in units of 0.02 micro-seconds. If any AT or ATD/RTD value has changed more than the value in this field since the last RIT Measurement Response, a new RIT Measurement Response message is sent. This field is optional. If this field is included, RIT Measurement Responses shall be send when some RIT value has changed more than this limit.

Range: 1-255

Deviation Limit

This field indicates the limit for the deviation of the AT or ATD/RTD values. If any time the predicted AT or ATD/RTD value (based on reported AT or ATD/RTD values and changes in the last RIT Measurement Response) has deviated more than the value in this field compared to the current measurement result, a new RIT Measurement Response message is sent. This field is optional. If this field is included, RIT Measurement Responses shall be send when the first deviation of some RIT value is more than this limit. The values are in units of 0.02 micro-seconds.

Range: 1-255

NOTE: Predicted AT or ATD/RTD value means the value that is calculated (extrapolated) based on AT or ATD/RTD value and AT or ATD/RTD Change value in last RIT Measurement Response message.

Monitor Period

This field indicates the requested time period for monitoring the time derivative of AT or ATD/RTD values, i.e. on how long monitor period the reported AT or ATD/RTD change is based. The value is in tens of seconds. This field is optional

Range: 1- 6

Environment Characterization

Environment Characterization field gives a LMU information about expected multipath and NLOS in the area.

‘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

‘4’: reserved (i.e. several values should be reserved)

Neighbor Number

This field indicates the maximum number of neighbor BTSs that the LMU should try to report.

Range: 0-15

Neighbor Type

This field indicates which neighbor BTSs are used for RIT measurements. If the value of the Neighbor Number field is lower than the total number of BTSs in the required list, then the BTS are selected in the order of the list.

‘0’: Neighbor BTSs listed in the BTS List IE are used for RIT measurements in the order of the list.

‘1’: If possible, neighbor BTSs listed in the BTS List IE are used, otherwise neighbors received in SYSTEM INFORMATION 2 or 5 message are used in the order of received signal strength.

‘2’: Neighbor BTSs indicated in SYSTEM INFORMATION TYPE 2 or 5 are used for RIT measurements (i.e. this is normal operation) in the order of received signal strength.

‘3’: All neighbor BTSs that can be received (i.e. reported BTSs are not limited to BTSs listed in SYSTEM INFORMATION TYPE 2 or 5 or BTS List IE). Support of this option in LMU is optional.

CellIdMethod

CellIdMethod field indicates whether CI or BSIC and BCCH carrier is used to identify neighbor BTSs in RIT Measurement Responses.

‘0’ = BSIC and BCCH carrier are used to identify the cell, even if CI is available.

‘1’ = CI is used to identify the neighbor cell, if it is available, otherwise BSIC and BCCH carrier are used.

A.2.1.1.3 BTS List IE

This information element indicates neighbor BTSs that are used for RIT measurements. This IE is conditional. If Neighbor Type field in the Measurement Instructions IE is ‘0’ or ‘1’ this field must be included. The first BTS on the list is the reference BTS that should be used as reference when reporting the RTD or AT values. If this reference BTS is not available, the LMU can select the used reference BTS based on signal strength.

This IE contains the following fields.

Number of BTSs

This field indicates, how many BTSs are included in this IE.

Range: 1 to 31.

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

CI

This field indicates the Cell Identity of the particular BTS. The purpose of the Cell Identity value is to identify a BTS within a location area.

Range: 0 – 65535

NOTE: Here is assumed that when LMU starts to make measurements, it firsts goes to the requested frequencies, and starts to decode BSICs and CIs from those specific frequencies. Because of this procedure the risk that there would be two BTSs with same CIs and same Channel numbers is minimal (i.e. there is no need to transmit LAC).

Time Slot Scheme

The Time Slot Scheme field indicates what kind of transmission scheme the particular BTS is using. If the LMU measures signals from BTSs from other time slots 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 LMU averages bursts from different time slots, and the BTS uses varying lengths of bursts.)

‘0’ = the burst scheme is unknown (The time slot should remain the same)

‘1’ = all time slots are 156.25 bits long

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

BSIC

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

Range: 0 – 63

BCCH Carrier

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

Range: 0 – 1023

A.2.2 RIT Measurement Response Message

The RIT Measurement Response is a message from the LMU to the SMLC. It is the response to the RIT Measurement Request. It contains the following information elements.

Table A.2: RIT Measurement Response message content

Information element

Type/Reference

Presence

Message Type

Message Type A.2.2.1.1

M

RIT Measurement

RIT Measurement A.2.2.1.2

M

A.2.2.1 RIT Measurement Response Message Information Elements

A.2.2.1.1 Message type IE

This IE contains the type of the message. This IE is mandatory.

A.2.2.1.2 RIT Measurement IE

This IE includes the required RIT measurements. The length of this IE depends on the number of measured neighbor BTSs. This IE is mandatory.

Reference LAC

This field indicates the Location Area Code of the reference BTS. The purpose of the Location Area Code is to identify a location area.

Range: 0 – 65535

Reference CI

This field indicates the Cell Identity value of the reference BTS. The purpose of the Cell Identity value is to identify a cell within a location area.

Range: 0 – 65535

Reference Frame Number

This field indicates the frame number of the last measured burst from the reference BTS.

Range: 0 – 2715647

Response Type

This field indicates whether AT of reference BTS is reported or not.

‘0’: AT of reference BTS is not reported

‘1’: AT of reference BTS is reported

Common Clock

This field indicates the type of the common reference clock for AT measurement. This field is included only if the Response Type field is ‘1’.

‘0’: GPS clock is used.

‘1’: Reserved for future use (e.g. Synchronized atomic clocks, or GLONASS)

Reference AT

This field indicates the measured AT value for the serving BTS. It is the starting moment of a time slot. It is counted in two parts: seconds after last minute change, and nanoseconds after last second change.This field is included only if the Response Type field is ‘1’.

Range:

seconds: 0-59

nanoseconds: 0-999,999,999

Reference AT Quality Resolution

Reference AT Quality Resolution field includes the resolution used in Reference AT Quality field. Encoding on 2 bits as follows

’00’ 0.005 micro seconds

’01’ 0.01 micro seconds

’10’ 0.05 micro seconds

’11’ Reserved.

This field is included only if the Response Type field is ‘1’.

Reference AT Quality

Reference AT Quality field includes the quality of reported RIT measurement. This Reference AT Quality field can be e.g. used to evaluate the reliability of AT measurements in the SMLC. Reference AT quality is defined as

Reference AT Quality == Std of reported AT value,

where is the reported Reference AT value and is its expectation value. The reporting resolution of Reference AT Quality is defined by Reference AT Quality resolution field.

Range: 0 to 63

Value 63 means that Reference AT Quality is greater than or equal to R*63, where R is the resolution defined in Reference AT Quality Resolution field.

This field is included only if the Response Type field is ‘1’.

Reference AT Change

This field indicates the first time derivative of the AT value for the reference BTS. This value is based on measurements made during Monitor Period, if the monitoring period is provided. Otherwise it is the best estimate of AT Change value at the time of last AT measurement. This field is conditional and included if Response Type field is ‘1’ . The range is -0.05 … 0.05 ppm and resolution is 0,00005 ppm.

Range: -1000 … 1000

Reference AT Change Quality Resolution

Reference AT Change Quality Resolution field includes the resolution used in Reference AT Change Quality field. Encoding on 2 bits as follows

’00’ 0.00005 ppm

’01’ 0.0001 ppm

’10’ 0.0005 ppm

’11’ Reserved.

This field is conditional and included if the Response Type field is ‘1’.

Reference AT Change Quality

Reference AT Change Quality field includes the quality of reported Reference AT Change. This Reference AT Change Quality field can be e.g. used to evaluate the reliability of RIT measurements in the SMLC. Reference AT Change Quality is defined as

Reference AT Change Quality == Std of reported AT Change value

where is the reported Reference AT Change and is its expectation value. The reporting resolution of Reference AT Change Quality is defined by Reference AT Change Quality Resolution field.

Range: 0 to 63

This field is conditional and included if the Response Type field is ‘1’.

Reference Time Slot

Reference Time Slot indicates the time slot relative to which the LMU reports the reference BTS measurements. This field is mandatory.

Range: 0 to 7

NOTE: If the LMU does not know timeslot scheme, the LMU reports the used timeslot. The LMU can only report results based on one time slot (N) or two time slots (N and N+4). If the LMU knows timeslot scheme, the LMU can make measurements from several timeslots and reports that the used timeslot is zero (and makes correction).

Reference RX Level

RX Level field includes the received signal strength of the reference BTS.

The RX Level is expressed in 2 dBm steps within the range -150 .. –24 dBm.

Range: 0 .. 63

ATD/RTD Quality Resolution

ATD/RTD Quality Resolution field includes the resolution used in ATD/RTD Quality field. Encoding on 2 bits as follows

’00’ 0.005 micro seconds

’01’ 0.01 micro seconds

’10’ 0.05 micro seconds

’11’ Reserved.

This field is mandatory.

ATD/RTD Change Quality Resolution

ATD/RTD Change Quality Resolution field includes the resolution used in ATD/RTD Change Quality field. Encoding on 2 bits as follows

’00’ 0.00005 ppm

’01’ 0.0001 ppm

’10’ 0.0005 ppm

’11’ Reserved.

This field is mandatory.

Number of Measured Neighbors

This field indicates the number of different neighbor BTSs.

NOTE: If the LMU can not measure any neighbor BTSs, then this value is set to ‘0’.

Range: 0 – 15

The following fields are repeated the number of times included in Number of Measured Neighbors field.

CellIdType

This field indicates is the identity method of the cell.

‘0’ = Cell identity is told using BSIC and BCCH carrier.

‘1’ = Cell identity is told using CI.

Neighbor CI

This field indicates the Cell Identity of the particular neighbor cell. The purpose of the Cell Identity value is to identify a cell within a location area.

Neighbor CI field is a conditional field and it is included only if CellIdType is set ‘1’ and CI value of the given cell is available.

Range: 0 – 65535

Neighbor BSIC

This field indicates the BSIC (Base Station Identity Code of the base station).

BSIC field is conditional and it is included only if CellIdType is set ‘0’.

Range: 0 – 63

Neighbor BCCH Carrier

This field indicates the absolute RF channel number of the neighbor base station. BCCH carrier field is conditional and it is included only if CellIdType is set ‘0’.

Range: 0 – 1023

Neighbor RX Level

RX Level field includes the received signal strength on the neighbor BTS.

The RX Level is expressed in 2 dBm steps within the range -150 .. –24 dBm.

Range: 0 .. 63

Neighbor Frame Number

This field indicates the calculated value of the neighbor BTS’s frame that would have been received at the same time or immediately after as the last measured frame from the reference BTS. This field is optional.

Range: 0 – 2715647

Neighbor Time Slot

Neighbor Time Slot indicates the time slot relative to which the LMU reports the serving BTS measurements. This field is mandatory.

Range: 0 to 7

NOTE: If the LMU does not know timeslot scheme, the LMU reports the used timeslot. The LMU can only report results based on one time slot (N) or two time slots (N and N+4). If the LMU knows timeslot scheme, the LMU can make measurements from several timeslots and reports that the used timeslot is zero (and makes correction).

ATD/RTD Value

This field indicates the measured ATD/RTD value between the receptions of signals from the reference and the neighbor BTS. This ATD/RTD value is the difference in reception of signal (the starting moment of time slot) from reference BTS compared to the signal (next starting moment of a time slot) from the neighbor BTS (i.e. this value is always positive). This field is mandatory. The reporting resolution of ATD/RTD value is 0.005 micro-seconds.

Range: 0 … 923200

NOTE: The reported ATD/RTD value may be based on some filtering or estimation algorithm. I.e. the reported value is not the last measurement result, it is the best estimate of real RTD value at the time of last measurement.

ATD/RTD Quality

ATD/RTD Quality field includes the quality of reported RIT measurement. This ATD/RTD Quality field can be e.g. used to evaluate the reliability of RIT measurements in the SMLC. ATD/RTD quality is defined as

ATD/RTD Quality = = Std of reported ATD/RTD value,

where is the reported ATD/RTD value and is its expectation value. The reporting resolution of ATD/RTD Quality is defined by ATD/RTD Quality resolution field.

Range: 0 to 63

This field is mandatory.

ATD/RTD Change

This field indicates the first time derivative of the ATD/RTD value between the receptions of signals from the reference and the neighbor BTS. This value is based on measurements made during Monitor Period, if the monitoring period is provided. Otherwise it is the best estimate of the ATD/RTD Change value at the time of last ATD/RTD measurement. The range is -0.1 … 0.1 ppm and resolution is 0,00005 ppm.

Range: -2000 … 2000

ATD/RTD Change Quality

ATD/RTD Change Quality field includes the quality of reported ATD/RTD Change. This ATD/RTD Change Quality field can be e.g. used to evaluate the reliability of RIT measurements in the SMLC. ATD/RTD Change Quality is defined as

ATD/RTD Change Quality == Std of reported ATD/RTD Change value,

where is the reported ATD/RTD Change and is its expectation value. The reporting resolution of ATD/RTD Change Quality is defined by ATD/RTD Change Quality resolution field.

Range: 0 to 63

This field is mandatory.

A.2.3 RIT Measurement Stop Message

The RIT Measurement Stop is a message from the SMLC to the LMU. It is sent when the SMLC wants the LMU to stop doing RIT measurements and reporting them. It contains the following information elements.

Table A.3: RIT Measurement Stop message content

Information element

Type/Reference

Presence

Message Type

Message Type A.2.3.1.1

M

A.2.3.1 RIT Measurement Stop Message Information Elements

A.2.3.1.1 1Message type IE

This IE contains the type of the message. This IE is mandatory.

A.2.4 RIT Measurement Error Message

The RIT Measurement Error is a message from the LMU to the SMLC. It is sent any time when the LMU can not perform RIT measurements asked for in the RIT Measurement Request. This message can be returned in return result (after reception of measurement command) or as separate message (during periodic measurement). It contains the following information elements.

Table A.4: RIT Measurement Error message content

Information element

Type/Reference

Presence

Message Type

Message Type A.2.4.1.1

M

Error Type

RIT Error Type A.2.4.1.2

M

RIT Error

RIT Error A.2.4.1.3

M

A.2.4.1 RIT Measurement Error Message Information Elements

A.2.4.1.1 Message type IE

This IE contains the type of the message. This IE is mandatory.

A.2.4.1.2 RIT Error Type IE

This IE indicates whether the error is temporarily (e.g. GPS reset) or permanent errors. Permanent error requires actions in SMLC, temporarily error informs that LMU can not send results temporarily (but it is expected to recover without any actions from SMLC).

‘0’ = Permanent error

‘1’ = Temporarily error

A.2.4.1.3 RIT Error IE

The purpose of the RIT Error IE is to provide the indication of error and the reason for it, when the LMU can not report required RIT results. This IE is mandatory. This IE has the following fields.

Error Reason

This field indicates the reason for error.

‘0’: There were no neighbor BTSs to be received.

‘1’: No ATD measurements were possible, since the common reference clock was not available.

‘2’: Requested type of measurements is not supported.

‘3’: Undefined error.

Annex B (informative):
TOA messages