08.713GPPLayer 3Location Services (LCS)Release 1999Serving Mobile Location Centre - Base Station System (SMLC-BSS) interfaceTS

2.1 General

This subclause defines the structure of the messages of the SMLC-BSS layer 3 protocol defined in 3GPP TS 03.71.

Each definition includes:

a) a brief description of the message;

b) a table listing the information elements in the order of their appearance in the message.

For each IE the table indicates:

1) the name of the IE (which gives an idea of the semantics of the element), which is used in this and other specifications as a reference to the IE within the message;

2) the name of the type of the IE (which indicates the coding of the value part of the IE), and a reference to a description of the value part of the IE;

3) the presence requirement indication (M, C or O) for the IE, as defined in 3GPP TS 04.07;

4) the format of the IE (T, V, TV, LV, TLV) as defined in 3GPP TS 04.07;

5) the length of the IE (or permissible range of lengths), in octets, in the message. The value of the length gives the number of octets in the IE following the length and element identifier. Where the length is encoded using more than one octet, the high order bit is bit 8 of the first (lowest numbered octet) and the low order bit is bit 1 of the last (highest numbered octet).

c) subclauses specifying conditions for IEs with presence requirement C or O in the relevant message. Together with other conditions specified in 3GPP TS 03.71 this defines when the IE shall be included or not, what non-presence of such IEs means, and (for IEs with presence requirement C) the static conditions for presence and/or non-presence of the IEs (see 3GPP TS 03.71).

2.2 Messages

The following Location Services related messages are exchanged between the SMLC and the BSS, with the VMSC acting as a relay.

1. TA Request

2. TA Response

3. TOA Request

4. TOA Response

5. Reject

6. Reset

7. Abort

8. TA Layer3

9. MS Position Command

10. MS Position Response

On the A interface the messages are contained in the Location Information IE which is encapsulated in the BSSMAP-LE Connection Oriented Information message as specified in 3GPP TS 08.08. On the Ls interface the messages are contained in the Location Information IE which is encapsulated in the BSSMAP–LE Connection Oriented Information message as specified in 3GPP TS 09.31.

2.2.1 TA Request

The TA Request is a message from the SMLC to the BSS, requesting BSS to return the timing advance (or access delay) of the MS.

Table 2.1: TA Request message content

2.2.2 TA Response

The TA Response is a message from the BSS to the SMLC. It is a response to TA Request message and contains the following information elements.

Table 2.2: TA Response message content

2.2.3 TOA Request

The TOA Request is a message from the SMLC to the BSS. It contains the following information elements.

Table 2.3: TOA Request message content

2.2.4 TOA Response

The TOA Response is a message from the BSS to the SMLC. It is a response to the TOA Request message. It contains the following information elements.

Table 2.4: TOA Response message content

2.2.5 Reject

The Reject is a message from the BSS to the SMLC. It is a possible response to TOA Request, TA Request or MS Position Command and contains the following information elements.

Table 2.5: Reject message content

The following are the expected cause values for Reject message:

– congestion;

– channel Mode not supported;

– positioning procedure not supported;

– failure for other radio related events;

– incorrect serving cell identity.

– BSSAP-LE Segmentation error

2.2.6 Reset

The Reset is a message from the BSS to the SMLC. It is sent when the Response message contents for a positioning request are invalidated (e.g. due to handover) before the positioning procedure was completed. The message may also be sent instead of a Reject when a TOA Request cannot be performed due to an error in the serving cell identity.

Table 2.6: Reset message content

The following are the expected cause values for Reset message:

– intra-BSS handover;

– failure for other radio related events;

– supervision Timer Expired;

– incorrect serving cell identity.

2.2.7 Abort

The Abort is a message either from the BSS to the SMLC or SMLC to the BSS. Upon receiving this signal, either SMLC or BSS shall abort ongoing positioning procedure.

Table 2.7: Abort message content

The following are the expected cause values for Abort message:

– failure for other radio related events;

– supervision Timer Expired;

– inter BSS handover;

– loss of signalling connection to MS.

2.2.8 TA Layer3

The TA Layer3 is an optional encapsulated message from the BSS to the SMLC that adds the following information in Complete layer 3 Information as described in 3GPP TS 08.08.

Table 2.8: TA Layer3 message content

2.2.9 MS Position Command

The BSSLAP MS Position Command is a message from the SMLC to BSS that contains the following information elements.

Table 2.9: MS Position Command message content

2.2.10 MS Position Response

The BSSLAP MS Position Response is a message from the BSS to the SMLC that contains the following information elements.

Table 2.10: MS Position Response message content