3 Message Structure

3GPP44.031Location Services (LCS)Mobile Station (MS) - Serving Mobile Location Centre (SMLC) Radio Resource LCS Protocol (RRLP)Release 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

3.1 General Format of RRLP Message

The general format of the RRLP message is given below, and based on:

– ITU-T Recommendation X.680;

– ITU-T Recommendation X.691;

and is consistent with these ITU-T recommendations. Also further definitions in the present document are based on ASN.1/94 defined in ITU-T Recommendation X.680 (ASN.1 1994). BASIC-PER, unaligned variant is used. Both RRLP ASN.1 modules, RRLP-Messages and RRLP-Components, are based on recommendations presented above.

ASN.1 identifiers have the same name as the corresponding parameters (information elements of the RRLP message, components, elements of components, fields of component elements etc) in other parts of the present document, except for the differences required by the ASN.1 notation (blanks between words are removed, the first letter of the first word is lower-case and the first letter of the following words are capitalized, e.g. "Reference Number" is mapped to "referenceNumber"). In addition some words may be abbreviated as follows:

msr measure

req request

rsp response

nbr number

ack acknowledgement

Ellipsis Notation shall be used in the same way as described in 3GPP TS 29.002 and shall be supported on the radio interface by the MS and the network for all operations defined in the present document.

Table 3.1.a: RRLP Message Format

RRLP-Messages

— { RRLP-messages }

DEFINITIONS AUTOMATIC TAGS ::=

BEGIN

IMPORTS

MsrPosition-Req, MsrPosition-Rsp, AssistanceData,

ProtocolError, PosCapability-Req, PosCapability-Rsp,

MultilaterationOTD-Req, MultilaterationOTD-Rsp,

PosMTA-Req

FROM

RRLP-Components — { RRLP-Components }

;

PDU ::= SEQUENCE {

referenceNumber INTEGER (0..7),

component RRLP-Component

}

RRLP-Component ::= CHOICE {

msrPositionReq MsrPosition-Req,

msrPositionRsp MsrPosition-Rsp,

assistanceData AssistanceData,

assistanceDataAck NULL,

protocolError ProtocolError,

…,

posCapabilityReq PosCapability-Req,

posCapabilityRsp PosCapability-Rsp,

multilaterationOTDReq MultilaterationOTD-Req,

multilaterationOTDRsp MultilaterationOTD-Rsp,

posMTAReq PosMTA-Req

}

END

The message consists of two information elements, that are further described in the following sub-clauses.

3.2 Reference Number IE

This element is mandatory, and appears only once per RRLP message. It has the range from 0 to 7. Value 0 is reserved for indicating unknown Reference Number. Its ASN.1 definition is in sub-clause 3.1. This element contains the Reference Number that shall be used as follows:

– in the Position Measurement procedure the SMLC shall select any number within the range 1- 7 that it is not already using with the particular MS. The Reference Number serves as an identification of the Measure Position request component that it sends to the MS. When the MS responds either with the Measure Position Response component, or the Protocol Error component, it shall use the same Reference Number value and, if an Extended Reference ID was included by the SMLC, the same Extended Reference ID to identify to which Measure Position Request it is responding, if the Reference Number has been obtained. If the MS has not been able to decode the Reference Number (e.g. IE missing), it shall use ‘0’ as the Reference number in the response. This mechanism helps for example in the cases where the SMLC sends a Measure Position Request to the MS, and before it receives the Response, it needs to send another Request (e.g. assistance data changes). Then the SMLC can identify to which Request the Response is related to;

– in the Assistance Data Delivery procedure the SMLC shall select any number within the range 1 – 7 that it is not already using with the MS. The Reference Number serves as an identification of the Assistance Data component that it sends to the MS. When the MS responds either with the Assistance Data Acknowledgement component or the Protocol Error component, it shall use the same Reference Number value if the Reference Number has been obtained and, in the case of Protocol Error, if an Extended Reference ID was included by the SMLC, the same Extended Reference ID to identify to which Assistance Data component it is responding. If the MS has not been able to decode the Reference Number (e.g. IE missing), it shall use ‘0’ as the Reference number in the response.

– in the Position Capability Transfer procedure the SMLC shall select any number within the range 1 – 7 that it is not already using with the MS. The Reference Number serves as an identification of the Positioning Capability Request component that it sends to the MS. When the MS responds either with the Positioning Capability Response component, or the Protocol Error component, it shall use the same Reference Number value if the Reference Number has been obtained and the same Extended Reference ID value if that has been obtained to identify to which Positioning Capability Request component it is responding. If the MS has not been able to decode the Reference Number (e.g. IE missing), it shall use ‘0’ as the Reference number in the response.

– the SMLC shall use the same Reference Number and same Extended Reference ID to resend any RRLP component for which a response was not received from the MS.

– the SMLC shall use a different Reference Number to that in any RRLP component for which a response was not received from the MS if the SMLC aborts an existing RRLP procedure and starts a new procedure.

– the SMLC may use the same Reference Number and same Extended Reference ID or different Reference Numbers and Extended Reference IDs for different RRLP components within the same pseudo-segmentation sequence.

In all RRLP messages except Assistance Data Acknowledgement, the Reference Number IE shall be supplemented by an Extended Reference IE in order to distinguish valid from invalid RRLP responses at the SMLC and duplicate from non-duplicate RRLP commands at the MS. In order to remain backward compatible, the receiving entity shall be able to receive Measure Position Request, Measure Position Response, Assistance Data and Protocol Error messages without the Extended Reference IE. The ASN.1 definition of the Extended Reference IE is given in sub-clause 5.1 and the procedures associated with sending and receiving it are given in clause 2 and in Annex A, sub-clauses A.2.2.5, A.3.2.7 and A.6.6.

3.3 Component IE

This element is mandatory, and appears only once per RRLP message. It contains the actual component to be transferred.

Different components are described further in Chapter 4. This IE contains only one component, i.e. it is not possible to include two or more components.