5 Information element encodings

3GPP48.071Layer 3 specificationLocation Services (LCS)Release 17Serving Mobile Location Centre - Base Station System (SMLC-BSS) interfaceTS

This paragraph contains the coding of the signalling elements used.

The following conventions are assumed for the sequence of transmission of bits and bytes:

– each bit position is marked as 1 to 8. Bit 1 is the least significant bit and is transmitted first;

– in an element octets are identified by number, octet 1 is transmitted first, then octet 2 etc.

When a field extends over more than one octet, the order of bit values progressively decreases as the octet number increases. The least significant bit of the field is represented by the lowest numbered bit of the highest numbered octet of the field.

– For variable length elements a length indicator is included, this indicates the number of octets following in the element.

– All fields within Information Elements are mandatory unless otherwise specified. The Information Element Identifier shall always be included.

All spare bits are set to 0.

The elements used and their coding are:

Table 5.1: Element Indentifier codes

Element Identifier Coding	Element name	Reference
0000 0001	Timing Advance	5.2
0000 1000	Reserved (note)
0000 1001	Cell Identity	5.4
0000 1010	Reserved (note)
0000 1011	Reserved (note)
0000 1100	Reserved (note)
0001 0000	Channel Description	5.8
0001 0001	Reserved (note)
0001 0010	Reserved (note)
0001 0011	Reserved (note)
0001 0100	Measurement Report	5.12
0001 0101	Reserved (note)
0001 1000	Cause	5.14
0001 1001	RRLP Flag	5.15
0001 1011	RRLP IE	5.16
0001 1100	Cell Identity List	5.17
0001 1101	Enhanced Measurement Report	5.18
0001 1110	Location Area Code	5.19
0010 0001	Frequency List	5.20
0010 0010	MS Power	5.21
0010 0011	Delta Timer	5.22
0010 0100	Serving Cell Identifier	5.23
0010 0101	Encryption Key (Kc)	5.24
0010 0110	Cipher Mode Setting	5.25
0010 0111	Channel Mode	5.26
0010 1000	MultiRate Configuration	5.27
0010 1001	Polling Repetition	5.28
0010 1010	Packet Channel Description	5.29
0010 1011	TLLI	5.30
0010 1100	TFI	5.31
0010 1101	TBF Starting Time	5.32
0010 1110	Power-Up Starting Time	5.32
0010 1111	Long Encryption Key (Kc128)	5.33
0011 0000	Concurrent Positioning Procedure Flag	5.34
NOTE: These values of the codepoints shall not be used as they were used in an earlier version of the protocol.

All unassigned codes are spare.

5.1 Message Type IE

Message Type uniquely identifies the message being sent. It is a single octet element, mandatory in all messages.

All unassigned codes are spare.

Table 5.1.1: Message Type codes

8 7 6 5 4 3 2 1
0 0 0 0 0 0 0 0	Reserved.
0 0 0 0 0 0 0 1	TA REQUEST
0 0 0 0 0 0 1 0	TA RESPONSE
0 0 0 0 0 1 0 0	Reserved (note)
0 0 0 0 0 1 0 1	Reserved (note)
0 0 0 0 1 0 1 0	REJECT
0 0 0 0 1 0 1 1	RESET
0 0 0 0 1 1 0 0	ABORT
0 0 0 0 1 1 0 1	TA LAYER3
0 0 0 0 1 1 1 1	MS Position Command
0 0 0 1 0 0 0 0	MS Position Response
0 0 0 1 0 0 0 1	U-TDOA Request
0 0 0 1 0 0 1 0	U-TDOA Response
NOTE: These values of the codepoints shall not be used as they were used in an earlier version of the protocol.

5.2 Timing Advance IE

This element contains the Timing Advance measured by the BTS.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Timing Advance								octet 2

Figure 5.2.1: Timing Advance IE

The coding of the timing advance value field is the binary representation of the timing advance in bit periods; 1 bit period = 48/13 us, as described in 3GPP TS 44.018 with the difference that all 8 bits are significant (instead of the normal 6 bits), which is necessary in order to report TA from extended range cells. To be correct, values over 63 do not correspond to a TA used by the MS (maximum is 63). Instead values over 63 correspond to the access delay measured by the BTS.

5.3 (void)

5.4 Cell Identity IE

This element defines the cell identity of the MS serving cell.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Cell Identity								octet 2-3

Figure 5.4.1: Cell Identity IE

The coding of the Cell Identity field is as defined in 3GPP TS 24.008 (excluding IEI).

5.5 (void)

5.6 (void)

5.7 (void)

5.8 Channel Description IE

This element defines the physical channel allocation of the MS.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Channel Description								octets 2-4

Figure 5.8.1: Channel Description IE

The coding of Channel Description field is as defined in 3GPP TS 44.018 (excluding IEI).

5.9 (void)

5.10 (void)

5.11 (void)

5.12 Measurement Report IE

This element contains the measurement report from the BSS.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Length								octet 2
Measurement Results								octet 3-18

Figure 5.12.1: Measurement Report IE

The Measurement Results field is encoded as in 3GPP TS 44.018 (excluding IEI) with the changes specified below.

DTX-USED
The DTX-USED bit shall be set as the DTXd field in the UPLINK MEASUREMENTS message in 3GPP TS 48.058.
If the DTX-USED field is set to "0" the SMLC shall use the RXLEV-FULL and RXQUAL-FULL values.
If the DTX-USED field is set to "1" the SMLC shall use the RXLEV-SUB and RXQUAL-SUB values.

RXLEV-FULL-SERVING-CELL and RXLEV-SUB-SERVING-CELL
When the values of RXLEV-FULL-SERVING-CELL and RXLEV-SUB-SERVING-CELL from TS 44.018 are 0 or 63, then their value shall be encoded to the Measurement Results without change. Otherwise, the values of RXLEV-FULL-SERVING-CELL and RXLEV-SUB-SERVING-CELL shall be added with 2 times the power reduction value corresponding to the Power Level field in the BS POWER message in 3GPP TS 48.058. A result higher than the upper boundary shall be limited to 63 to avoid value out of range.

RXLEV-FULL-SERVING-CELL (parameter in Measurement Results)
= RXLEV-FULL-SERVING-CELL (parameter from TS 44.018, in octet 2 of NMR section 10.5.2.20 )
+ 2*( Power Level field in the BS POWER message)

RXLEV-SUB-SERVING-CELL (parameter in Measurement Results)
= RXLEV-SUB-SERVING-CELL (parameter from TS 44.018)
+ 2*( Power Level field in the BS POWER message)

Example: If Power Level is "0010" then
RXLEV-FULL-SERVING-CELL (parameter in Measurement Results)
= RXLEV-FULL-SERVING-CELL (parameter from TS 44.018) + (2*2)

5.13 (void)

5.14 Cause IE

This element contains the cause value.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Cause value								octet 2

Figure 5.14.1: Cause IE

The cause field is coded as follows:

Table 5.14.1: Cause IE coding

0000 0000	Congestion
0000 0001	Channel Mode not supported
0000 0010	Positioning procedure not supported
0000 0011	Failure for other radio related events
0000 0100	Intra-BSS handover
0000 0101	Supervision Timer Expired
0000 0110	Inter-BSS handover
0000 0111	Loss of signalling connection to MS
0000 1000	Incorrect serving cell identity
0000 1001	BSSAP-LE Segmentation error
0000 1010	Concurrent Positioning Procedure not enabled
All unassigned codes are spare.

5.15 RRLP Flag IE

This element is coded as:

8	7	6	5	4	3	2	1
Element identifier								octet 1
SPARE							Flag1	octet 2

Figure 5.15.1: RRLP Flag IE

The fields are coded as follows:

Flag 1 (Octet 2, bit 1):

0 Position Command (SMLC to BSC) or final response (BSC to SMLC).

1 Not a Positioning Command or final response.

5.16 RRLP IE

RRLP IE is coded as:

8	7	6	5	4	3	2	1
Element identifier								octet 1
Length								octet 2-3
RRLP APDU (3GPP TS 44.031)								octet 4-n

Figure 5.16.1: RRLP IE

5.17 Cell Identity List IE

This element defines the list of cell identities of neighbour cells, for which measurements are reported. The Cell Identities are listed in the same order than the corresponding measurements in the (Enhanced) Measurement Report IE.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Length								octet 2
Spare				Cell identification Discriminator 1				octet 3
Cell Identification 1								octet 4 to (4+p)
…
Spare				Cell identification Discriminator N				octet (n-q-1)
Cell Identification N								octet (n-q) to n

Figure 5.17.1: Cell Identity IE

The coding of octet 2 is a binary number indicating the Length of the remaining element. The Length depends on the Cell identification discriminator i as well as the number of cells to be identified.

The Cell identification discriminator i is coded as follows:

0000 The whole Cell Global Identification, CGI, is used to identify the 2G cells.

0001 Location Area Code, LAC, and Cell Identify, CI, are used to identify the 2G cells.

0010 3G Cell identification container 1.

0011 3G Cell identification container 2.

All other values are reserved.

The coding of the Cell Identification i depends on the Cell identification discriminator i. Below the coding of the i-th Cell Identification is shown for each Cell identification discriminator (with "i" in the range 1 to n):

Coding of the i-th Cell Identification for Cell identification discriminator = 0000.

8	7	6	5	4	3	2	1
MCC dig 2				MCC dig 1				octet x+1
MNC dig 3				MCC dig 3				octet x+2
MNC dig 2				MNC dig 1				octet x+3
LAC								octet x+4
LAC cont.								octet x+5
CI value								octet x+6
CI value cont								octet x+7

Figure 5.17.2: Cell identification for discriminator = 0000

The octet (x+2) bits 5-8 are filled by ‘1111’ if 2 digit MNC is used.

The octets (x+1)-(x+5) are coded as the value part shown in 3GPP TS 24.008, Table ‘Location Area Identification information element’.

The octets (x+6)-(x+7) are coded as the value part shown in 3GPP TS 24.008, Table ‘Cell Identity information element’.

Coding of i-th Cell Identification for Cell identification discriminator = 0001.

8	7	6	5	4	3	2	1
LAC								octet x+1
LAC cont.								octet x+2
CI value								octet x+3
CI value cont								octet x+4

Figure 5.17.3: Cell identification for discriminator = 0001

The octets (x+1)-(x+2) are coded as the value part shown in 3GPP TS 24.008, Table ‘Location Area Identification information element’.

The octets (x+3)-(x+4) are coded as the value part shown in 3GPP TS 24.008, Table ‘Cell Identity information element’.

Coding of the Target ID for Cell identification discriminator = 0010.

Octets (x+1) to (x+9) shall be ignored by the receiver.

NOTE: in the 3G Cell identification container 1, the transmitter may send PLMN-ID, LAC, RNC-ID and C-ID to identify a 3G cell.

Coding of the Target ID for Cell identification discriminator = 0011.

Octets (x+1) to (x+6) shall be ignored by the receiver.

NOTE: In the 3G Cell identification container 2, the transmitter may send LAC, RNC-ID and C-ID to identify a 3G cell.

5.18 Enhanced Measurement Report IE

This element contains the measurement report from the BSS.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Length								octet 2
Enhanced Measurement Results								octet 3-n

Figure 5.18.1: Enhanced Measurement Report IE

The Enhanced Measurement Results field is encoded as the contents of the ENHANCED MEASUREMENT REPORT message in 3GPP TS 44.018 (excluding the fields: "RR short PD", "Message type" and "Short layer 2 header") with the changes specified below.

RXLEV_VAL for serving cell
When the values of RXLEV_VAL from TS 44.018 is 0 or 63, then its value shall be encoded to the Enhanced Measurement Results without change. Otherwise, the value of RXLEV_VAL shall be added with 2 times the power reduction value corresponding to the Power Level field in the BS POWER message in 3GPP TS 48.058. A result higher than the upper boundary shall be limited to 63 to avoid value out of range.

RXLEV_VAL (parameter in Enhanced Measurement Results)
= RXLEV_VAL (parameter from TS 44.018 in section 9.1.55)
+ 2*(Power Level field in the BS POWER message)

Example: If Power Level is "0010" then
RXLEV_VAL (parameter in Enhanced Measurement Results)
= RXLEV_VAL (parameter from TS 44.018) + (2*2).

5.19 Location Area Code IE

This element defines the cell identity of the MS serving cell.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Location Area Code								octet 2-3

Figure 5.19.1: Location Area Code IE

The coding of the Location Area Code field is as defined in 3GPP TS 24.008 (excluding IEI, MCC, and MNC).

5.20 Frequency List IE

The Frequency List IE contains a list of frequencies used by the MS.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Length								octet 2
Frequency List								octets 3-n

Figure 5.20.1: Frequency List IE

The coding of Frequency List field is as defined in 3GPP TS 44.018 (excluding IEI and length field).

5.21 MS Power IE

This element contains the MS power.

8	7	6	5	4	3	2	1
Element identifier								octet 1
MS Power								octet 2

Figure 5.21.1: MS Power IE

The MS Power field is encoded as in 3GPP TS 44.018 (excluding IEI) and 3GPP TS 45.005.

5.22 Delta Timer IE

This element contains the value of the delta timer. The coding is as follows.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Timer Value								octet 2

Figure 5.22.1: Delta Timer IE

The Timer Value field is expressed in units of 0,1s.

5.23 Serving Cell Identifier IE

This element uniquely identifies a cell within a BSS and is of variable length containing the following fields:

8	7	6	5	4	3	2	1
Element identifier								octet 1
Length								octet 2
Spare				Cell identification discriminator				octet 3
Cell identification								octet 4-n

Figure 5.23.1: Serving Cell Identifier IE

The Serving Cell Identifier IE is encoded as in 3GPP TS 48.008 (excluding IEI and length field).

5.24 Encryption Key IE

This element defines the encryption key (Kc) of the MS being located.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Encryption Key (Kc)								octet 2-9

Figure 5.24.1: Encryption Key IE

The Encryption Key (Kc) field contains the ciphering key to be used in connection with the encryption algorithms A5/1 and A5/3 as provided to the BSS by the MSC in the Encryption Information IE and as defined in TS 48.008.

5.25 Cipher Mode Setting IE

The purpose of the Cipher Mode Setting information element is to indicate whether stream ciphering shall be started or not and if it is to be started, which algorithm to use.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Spare	Ciph Mod Set IEI			algorithm identifier			SC	octet 2

Figure 5.25.1: Cipher Mode Setting IE

The Cipher Mode Setting information element is coded as defined in TS 44.018 (excluding IEI).

5.26 Channel Mode IE

The purpose of the Channel Mode information element is to indicate the mode on coding/decoding and transcoding.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Mode								octet 2

Figure 5.26.1: Channel Mode IE

The Channel Mode information element is coded as defined in TS 44.018 (excluding IEI).

5.27 MultiRate Configuration IE

The purpose of the MultiRate Configuration information element is to provide all parameters relevant to multi-rate speech codec.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Length								octet 2
Multirate speech version			NSCB	ICMI	Spare	Start mode		octet 3
Parameters for multirate speech								octet 4 – n

Figure 5.27.1: MultiRate Configuration IE

The MultiRate Configuration information element is coded as defined in TS 44.018 (excluding IEI).

5.28 Polling Repetition IE

This element contains the value of the number of repetitions of the Packet Polling Request procedure. The coding is as follows:

8	7	6		5	4	3	2	1
Element identifier									octet 1
Spare			Number of polling repetitions (binary)						octet 2

Figure 5.26.1: Polling Repetition IE

The Polling Repitition IE is a binary representation in the range of 4-63.

5.29 Packet Channel Description IE

This element contains the timeslot allocation and frequency parameters. The coding is as follows.

8	7	6	5	4	3	2	1
Element identifier								octet 1
CSN.1 binary representation of the channel parameters as described in TS 44.018 (CCCH) or TS 44.060 (PCCCH) plus padding bits (binary 0) as required to achieve 4 complete octets								octets 2-5

Figure 5.29.1: Packet Channel Description IE

5.30 TLLI IE

The purpose of the TLLI information element is to provide the Temporary Logical Link Identifier.

8	7	6	5	4	3	2	1
Element Identifier								octet 1
TLLI value								octet 2
TLLI value (contd)								octet 3
TLLI value (contd)								octet 4
TLLI value (contd)								octet 5

Figure 5.30.1: TLLI IE

The TLLI information element is coded as defined in TS 44.018 (excluding IEI).

5.31 TFI IE

This element contains the value of the TFI. The coding is as follows.

8	7	6	5		4	3	2	1
Element identifier									octet 1
Spare				TFI					octet 2

Figure 5.31.1: TFI IE

The TFI information element is coded as defined in TS 44.060 (excluding IEI).

5.32 Starting Time IE

The purpose of the Starting Time information element is to provide the start TDMA frame number, FN modulo 42432 of the first transmission of the Packet Polling Request or first block of user data associated with the U-TDOA location method from the BSS to the MS. In the case that the power-up procedure for U-TDOA is supported, the Starting Time information element may provide the starting frame number of the power-up and DTX suspension.

8	7	6	5	4	3	2	1
Element Identifier								octet 1
T1′					T3 (high part)			octet 2
T3 (low part)			T2					octet 3

Figure 5.32.1: Starting Time IE

The Starting Time information element is coded and interpreted as defined in TS 44.018 (excluding IEI).

5.33 Long Encryption Key IE

This element defines the 128 bit encryption key (Kc128) of the MS being located.

8	7	6	5	4	3	2	1
Element identifier								octet 1
Long Encryption Key (Kc128)								octet 2-17

Figure 5.24.1: Long Encryption Key IE

The Long Encryption Key (Kc128) field contains the ciphering key to be used in connection with encryption algorithm A5/4 as provided to the BSS by the MSC as defined in TS 48.008.

5.34 Concurrent Positioning Flag

This element contains the current BSC capability of the second, concurrent, independent location method. The coding is as follows:

8	7	6	5	4	3	2	1
Element identifier								Octet 1
Concurrent Method Flag								Octet 2

Figure 5.34.1: Concurrent Positioning IE

Table 5.34.1: Concurrent Method Flag Coding

Coding	Element name
0000 0000	Second independent concurrent positioning Allowed
1111 1111	Second independent concurrent positioning Disallowed
NOTE: All other values reserved

The combinations of first and second location procedures in concurrent positioning are limited to the following:

Figure 5.34.2 Allowed Concurrent Positioning Procedures

First Location Procedure	Second Location Procedure
TA Positioning	MS Positioning
UTDOA Positioning	MS Positioning
MS Positioning	TA Positioning
MS Positioning	U-TDOA Positioning

Annex A (informative):
Change History

Meeting/Date	Tdoc	CR	Rev	Subject/Comment	New version
January 2016				Version 13.0.0 based on version 12.0.0	13.0.0

Change history
Date	Meeting	TDoc	CR	Rev	Cat	Subject/Comment	New version
2017-03	RP-75	–	–	–	–	Version for Release 14 (frozen at TSG-75)	14.0.0
2018-06	RP-80	–	–	–	–	Update to Rel-15 version (MCC)	15.0.0
2020-07	RP-88e	–	–	–	–	Upgrade to Rel-16 version without technical change	16.0.0
2022-03	RP-95e	–	–	–	–	Upgrade to Rel-17 version without technical change	17.0.0