7 General message format and information elements coding
3GPP44.071GSM/EDGE Location Services (LCS)Mobile radio interface layer 3 LCS specificationRelease 17TS
The figures and text in this clause describe message contents. Within each octet, the bit designated "bit 1" is transmitted first, followed by bits 2, 3, 4, etc. Similarly, the octet shown at the top of each figure is sent first.
7.1 Overview
Within the layer 3 protocol defined in the present document, every message is a standard L3 message as defined in 3GPP TS 24.007. This means that the message consists of the following parts:
a) protocol discriminator;
b) transaction identifier;
c) message type;
d) other information elements, as required.
Unless specified otherwise, a particular information element may be present only once in a given message.
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.
7.2 Protocol discriminator
The Protocol Discriminator (PD) and its use are defined in 3GPP TS 24.007. The present document defines the protocols relating to the PD values:
1 1 0 0 location services
7.3 Transaction identifier
For general rules, format and coding of transaction identifier values, see 3GPP TS 24.008.
7.4 Message type
The message type IE and its use are defined in 3GPP TS 24.007. Table 7.4 defines the value part of the message type IE used in the location service protocol.
Table 7.4: Message types
|
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
Message types |
|
|
0 |
X |
1 |
0 |
. |
. |
. |
. |
Clearing messages: |
|
|
0 |
0 |
0 |
1 |
– RELEASE COMPLETE |
|||||
|
0 |
X |
1 |
1 |
. |
. |
. |
. |
Miscellaneous message group: |
|
|
0 |
0 |
0 |
1 |
– FACILITY |
|||||
|
0 |
0 |
1 |
0 |
– REGISTER |
|||||
|
NOTE 1: Bit 8 is reserved for possible future use as an extension bit, see 3GPP TS 24.007. NOTE 2: Bit 7 is reserved for the send sequence number in messages sent from the LMU. In messages sent from the SMLC, bit 7 is coded with a "0", see 3GPP TS 24.007. |
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7.5 Facility information element
The purpose of the Facility information element is to indicate the invocation and operation of location services, identified by the corresponding operation code within the Facility information element.
The Facility information element is coded as shown in figure 7.5 and clause 8.
The Facility is a type 4 information element with no upper length limit except that given by the maximum number of octets in a L3 message, see 3GPP TS 44.006.
|
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
|
|
Facility IEI |
octet 1 |
|||||||
|
Length of Facility contents |
octet 2 |
|||||||
|
Component(s) (note) |
octet 3 etc. |
|||||||
|
NOTE: This component contains Transparent LCS Information. Encoding of this component is according to clause 8. |
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Figure 7.5: Facility information element
7.6 Release forbidden
This information element is used only in SMLC to LMU messages. The presence of IE indicates that the release of LCS transaction is not allowed by LMU.