B.2 Information element encodings

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

B.2.1 Message Type IE

This IE contains the type of the message.

Range: 0 – 255

B.2.2 Measurement Device Info IE

This IE indicates the LMU Measurement Devices that are addressed with the message. (One physical LMU may contain several devices, e.g. an LMU co-located with a three sector site would normally contain three devices). It contains the following fields:

Number of Measurement Devices

This field indicates the number of LMU Measurement Devices that are addressed with the message. This field is mandatory.

Range: 1-6

The following field is repeated "Number of Measurement Devices" times.

Measurement Device ID

This field indicates the ID of the LMU Measurement Device.

Range: 0 -5

B.2.3 Channel Description IE

The purpose of the Channel Description IE is to inform the LMU about the physical channel used by MS. This IE contains the following fields:

Frequency List Type

This field describes the format of the frequency information. If both frequency list and index is provided then the LMU shall store the frequency list and its associated index. If only an index is provided the LMU shall use the associated frequency list.

‘0’: Frequency list only

‘1’: Frequency list and index

‘2’: Frequency list index only

Frequency list index

This field identifies a frequency list either provided with this message or stored by the LMU. This field is present when "Frequency List Type" is equal to 1 or 2.

Range: 0-31

Number of ARFCNs

This field indicates the number of frequencies used by MS. This field is present if "Frequency List Type" is equal to 0 or 1.

Range: 1-64

The following field is repeated the number of times indicated by the "Number of ARFCNs" field.

ARFCN

This field indicates the absolute radio frequency number. This field is present if "Frequency List Type" is equal to 0 or 1.

Range: 0-1023

Hopping

This field indicates if frequency hopping is used. This field is mandatory.

‘0’: No hopping

‘1’: Hopping

MAIO

This field indicates the Mobile Allocation Index Offset used in the frequency hopping algorithm (see 3GPP TS 05.02). This field is present if Hopping=’1′.

Range: 0-63

HSN

This field indicates the Hopping Sequence Number used in the frequency hopping algorithm (see 3GPP TS 05.02). This field is present if Hopping=’1′.

Range: 0-63

Frame Number

This field indicates the Frame Number modulo 84864 of the first burst expected from the MS. It is used in the frequency hopping algorithm (see 3GPP TS 05.02). This field is present if Hopping=’1′.

Range: 0-84863

Channel Type

This field indicates the channel type. This field is mandatory.

‘0’: TCH/F

‘2’: TCH/H SCN=0

‘3’: TCH/H SCN=1

Number of Bursts

This field indicates the number of bursts to measure TOA on. This field is mandatory. The field is coded as follows

Value Number of Bursts

0 5

1 10

2 20

3 40

4 70

5 140

6 280

7 560

B.2.4 Signal Description IE

The purpose of the Signal Description IE is to inform the LMU about the signal transmitted by MS. It contains the following fields:

Burst Type

This field contains the burst type transmitted by MS.

‘0’: Access Burst

‘1’: Normal Burst

Handover Reference

This field contains the handover reference number which together with BSIC completely defines the data portion of the access burst. This field is present when Burst Type = ‘0’.

Range: 0 -255

BSIC

This field indicates the BSIC (Base Station Identity Code) which together with Handover Reference Number defines the data portion of an access burst. This field is present when Burst Type= ‘0’.

Range: 0 – 63

TSC

This field indicates the Training Sequence Code used by MS. This field is present when Burst Type=’1′.

Range: 0-7

B.2.5 Timing Description IE

This IE provides information about the predicted arrival time of MS signals. It contains the following fields:

Time Reference

This field indicates the used clock reference. This field is mandatory.

‘0’: GPS time

‘1’: GSM time

‘2’-‘3’: Reserved for future use

GPS Start Time

This field indicates the predicted signal arrival time expressed in GPS time. The signal arrival time (TOA) is defined as the start point of a time slot. It is counted in units of 4 micro-second modulo 60s. To remove any ambiguity, let RT denote the reception time, ST denote the start time, and T an arbitrary time. Then if

1) (ST-RT) mod 60s <= 40s

then the indicated start time is the next time when T mod 60s is equal to ST.

It is possible that a request arrives late so that 1) is not fulfilled but before all bursts have been transmitted. It is in such a case possible to perform measurements on the remaining bursts if condition

2) (RT-ST) mod 60s  .

is fulfilled. Here  denotes the length of the complete measurement interval. It can be derived from the fields Channel Type and the Number of Bursts.

Should however neither of 1) or 2) be fulfilled then the request arrived too late and the bursts were missed.

This field is present when Time Reference=’0′

Range: 0 – 14,999,999

GPS SV

This IE identifies a GPS clock SV (Space Vehicle) used for time stamping. Value 0 means that all available GPS sources should be used for deriving a time stamp. This field is present if Time Reference = ‘0’.

Range: 0-31

BCCH

This field indicates the ARFCN (BCCH) of the BTS whose clock is used as reference for Start Time. This field is present when Time Reference=’1′.

Range: 0 – 1023

BSIC

This field indicates the Base Station Identity Code of the BTS whose clock is used as reference for Start Time. This field is present when Time Reference=’1′.

Range: 0 – 63

GSM Start Time

This field indicates the predicted signal arrival time expressed in GSM time. It is expressed as Frame Number FN modulo 42432, Time slot Number TN and Bit Number BN. The reference point for signal arrival time (TOA) is defined as the start point of a time slot. The start time can encode only an interval of time of 42 432 frames, that is to say around 195.8 seconds. To remove any ambiguity, let RFN denote the frame number at reception, and FN’ denote an arbitrary frame number. Then if

1) (FN-RFN) mod 42432  31623

then the indicated starting FN is the next time when FN’ mod 42432 is equal to FN.

It is possible that a request arrives late so that 1) is not fulfilled but before all bursts have been transmitted. It is in such a case possible to perform measurements on the remaining bursts if the condition

2) (RFN-FN) mod 42432  .

is fulfilled. Here  denotes the length of the complete measurement interval. It can be derived from the fields Channel Type and the Number of Bursts.

Should however neither of 1) or 2) be fulfilled then the request arrived too late and the bursts were missed.

This field is present when Time Reference=’1′. It contains the following subfields:

FN (mod 42432):

Range: 0 – 42432

TN:

Range: 0 – 7

BN:

Range: 0 – 156

Start Time Uncertainty

This field indicates the uncertainty in the arrival of the signal from MS. Expressed in GSM bit periods (i.e. 48/13 micro-seconds). The burst is expected to arrive in the interval

[Start Time – Start Time Uncertainty, Start Time + Start Time Uncertainty]

This field is mandatory. The field is coded as follows.

Value Uncertainty

0 2

1 3

2 4

3 5

4 7

5 10

6 13

7 17

8 20

9 25

10 35

11 45

12 55

13 65

14 90

15 140

B.2.6 Measurement Options IE

This IE indicates options for TOA measurement. It contains the following fields.

Method

This field defines the TOA algorithm to be used by LMU. A value of zero indicates that a default algorithm may be used. Remaining values are vendor specific. This field is mandatory.

Range: 0 – 7

Environment Characterization

This field indicates the expected multipath environment. This field is mandatory.

‘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)

Measurement Type

This field indicates whether LMU shall include an estimate of the Time of Arrival (TOA) and/or Angle of Arrival (AOA) with the measurement result.

‘0’: Report TOA only

‘1’: Report AOA only

‘2’: Report TOA and AOA

B.2.7 Number of Measurement Devices IE

This IE indicates the number of LMU Measurement Devices that are reporting with the message.

Range: 1-6

B.2.8 Timing Info IE

This IE provides information about the used clock source for TOA measurement. It contains the following fields:

Time Reference

This field indicates the used clock reference. This field is mandatory.

‘0’: GPS time

‘1’: GSM time

‘2’-‘3’: Reserved for future use

BCCH

This field indicates the ARFCN (BCCH) of the BTS whose clock is used as clock reference. This field is present when Time Reference=’1′.

Range: 0 – 1023

BSIC

This field indicates the Base Station Identity Code of the BTS whose clock is used as clock reference. This field is present when Time Reference=’1′.

Range: 0 – 63

B.2.10 Measurement Device ID IE

This IE indicates the ID of the reporting LMU Measurement Device.

Range: 0 -5

B.2.11 Measurement Info IE

This IE indicates additional information related to the signal measurement.

Method

This field indicates the used method for TOA measurement. This field is mandatory.

Range: 0 – 7

Diversity

This field indicates if diversity was used for measurements. This field is mandatory.

‘0’: Diversity was not used.

‘1’: Diversity was used.

Measured Number of Bursts

This field indicates the number of bursts used for TOA measurement. It is expressed as a ratio N = (number measured)/(number requested). This field is mandatory. It is coded as follows.

0 0  N < 1/7

1 1/7  N < 2/7

2 2/7  N < 3/7

3 3/7  N < 4/7

4 4/7  N < 5/7

5 5/7  N < 6/7

6 6/7  N < 1

7 N=1

Angle of Arrival

This field indicates the Angle of Arrival in units of 0.1 degrees. This field is optional.

Range: 0 – 3599

AOA Uncertainty

This field indicates the quality of Angle of Arrival (AOA) estimate in units of 0.1 degrees. It is defined as follows. Let  denote the estimated AOA, 0 denote the true AOA, and r denote the uncertainty.
Then Prob(|-0| < r) = 67%, i.e. with 67% confidence the true AOA lies in the interval [-r, +r].
The uncertainty r, expressed in degrees, is mapped to a number K, with the following formula:

with C = 0.446 and x = 0,25. With 0 £ K £ 30, a useful range between 0.1 degrees and 360 degrees is achieved for the uncertainty. K is the value being sent. A value of 31 means that the measurement failed. This field is optional.

Range: 0 -31

B.2.12 Number of Peaks IE

This IE indicates the number of peaks (i.e. TOA values) reported.

Range: 0 – 4

B.2.13 Measured TOA IE

This IE indicates the absolute TOA value (modulo the duration of a TDMA frame) determined by LMU. Expressed in units of 0.004 micro-seconds relative to the starting time.

Range: -131072 – +131071

B.2.14 TOA Quality IE

This IE indicates the TOA quality determined by LMU. It contains the following fields:

TOA Uncertainty

This field indicates the uncertainty of the TOA estimate. It is defined as follows. Let  denote the estimated TOA, 0 denote the true TOA, and r denote the uncertainty. Then Prob(|-0| < r) = 67%, i.e. with 67% confidence the true TOA lies in the interval [-r, +r]. The uncertainty r, expressed in nanoseconds, is mapped to a number K, with the following formula:

with C = 25 and x = 0.12. With 0 £ K £ 62, a suitably useful range between 3 ns and 28 s is achieved for the uncertainty. A value of 63 means that the measurement failed. This field is optional.

Range: 0 – 63

SNR Estimate

This field indicates the estimated Signal To Noise ratio. Values are expressed in steps of 1 dB ranging from –30 to + 33. This field is optional.

Range: 0 – 63

TOA Signal Strength

This field indicates the estimated Signal Strength. Values are expressed in steps of 2dBm from –150 to –24 dBm. This field is optional.

Range: 0 – 63

Annex C (informative):
Status Messages