4 General

24.5713GPP5G System (5GS)Control plane Location Services (LCS) proceduresRelease 17Stage 3TS

4.1 Overview

4.1.1 NAS aspect

To enable transfer of Location Services (LCS) signaling messages between the 5G core network (5GCN) and the UE, two Payload container types are defined in the downlink (DL NAS TRANSPORT message) and the uplink (UL NAS TRANSPORT message or CONTROL PLANE SERVICE REQUEST message). The message protocol and procedures are described in 3GPP TS 24.501 [3].

4.1.2 LCS aspect

LCS uses the defined payload container to transfer LCS signalling messages between the UE and the network.

The corresponding LCS signaling messages include:

a) LTE Positioning Protocol (LPP) messages (see 3GPP TS 37.355 [4])

– Both downlink and uplink LPP messages are supported

– Routing information is transported as the Additional information IE in UL/DL NAS TRANSPORT message for LPP messages (see 3GPP TS 24.501 [3])

b) Location services messages

– Messages for MO-LR operations (see 3GPP TS 24.080 [5])

– Messages for LocationNotification operations (see 3GPP TS 24.080 [5])

– Messages for EventReport operations (see 3GPP TS 24.080 [5])

– Messages for PeriodicTriggeredInvoke operations (see 3GPP TS 24.080 [5])

– Messages for CancelDeferredLocation operations (see 3GPP TS 24.080 [5])

– Messages for MSCancelDeferredLocation operations (see 3GPP TS 24.080 [5])

– Messages for LocationPrivacySetting operations (see 3GPP TS 24.080 [5])

Routing information associated with the LMF is transported as the Additional information IE in UL/DL NAS TRANSPORT message or CONTROL PLANE SERVICE REQUEST message (see clause 5.2.2.6.1) for Location services messages that are transported between the UE and the LMF (see 3GPP TS 24.501 [3])

The Routing information transported as the Additional Information IE can be Routing identifier in the current specification, which includes immediate routing identifier and deferred routing identifier. The immediate routing identifier transported as the Additional Information IE is the Correlation ID, which is allocated by the AMF and can be used in the UL/DL NAS TRANSPORT message (see clause 5.2 and clause 5.3). The deferred routing identifier transported as the Additional Information IE can be used in the UL NAS TRANSPORT and CONTROL PLANE SERVICE REQUEST message for the AMF routing the LCS messages to the particular LMF (see clause 5.2.2).

4.2 LCS Support capabilities

4.2.1 UE support of LCS

The UE announces to the network its ability to support LCS notification mechanism or LPP messages or both, using the 5GMM capability IE defined in 3GPP TS 24.501 [3].

4.2.2 Network support of LCS

The network announces to the UE its ability to support LCS in 5GC using the 5GS network feature support IE defined in 3GPP TS 24.501 [3]. The information is taken into account by the UE, in addition to UE’s LCS capabilities, for the UE to determine whether to initiate MO-LR procedure in NG-RAN as specified in 3GPP TS 23.273 [3], clause 6.2.

NOTE: An SNPN can provide Location Services except for the cases of interworking with EPC, roaming, and direct access to SNPN via non-3GPP access, which are not supported in an SNPN.