7 Signaling Protocols and Interfaces

23.1713GPPFunctional descriptionLocation Services (LCS)Release 1999Stage 2 (UMTS)TS

7.1 Signalling protocols for LCS support in UMTS

7.1.1 Protocol layering

The Iu protocol stacks are defined in TS 25.410. The functions performed by each protocol layer are described in reference [1].

7.2 Iu interface

The Iu interface is used to communicate between the LCS functional entities in the Core Network and the LCS entities in the Access Network.

This interface passes the location requests and responses from authenticated external and internal LCS applications between the LCS entities in the Core Network and the Access Network LCS entities. Support for LCS signaling over Iu is specified in TS 25.413 RANAP signalling [14].

7.2.1 Core network location request

The core network request for a location estimate of a target MS shall contain sufficient information to enable location of the Target UE according to the required QoS using any positioning method supported by the PLMN and, where necessary, UE. For location services the core network may request the geographical co-ordinates of the Target UE. The core network may also request in which Service Area the Target UE is located. The Service Area information may be used for routing of corresponding Emergency calls, or for CAMEL services and this corresponds to the usage of Cell ID in the core network of GSM. (The MSC shall not send the Service Area Identity to GMLC).

It should be noted that the Service Area concept is different from the Localized Service Area concept used for SoLSA services.

When the location of a Target UE in Idle Mode is requested, the core network shall determine which RNC is associated with the Target UE.

7.2.2 Location Report

The access network reports the location of the Target UE to the core network entities via the Iu interface. The location report may contain the following information as defined in the corresponding location request:

– the geographical co-ordinates of the Target UE;

– the service area in which the Target UE is located;

– achieved quality level of the location estimate;

7.3 Uu Interface

The Uu interface is used to communicate among the LCS entities associated with the RNC, the UEs and the stand-alone Location Measurement Units (LMU). The Uu interface is also used to communicate between the LCS entities in the core network and the UE.

This interface may pass measurement requests and results to and from UE or the stand-alone LMU.

The Uu interface may also pass location requests from internal or external LCS Clients (Applications) at the UE. Note that these requests may require the services of the LCS entities associated with the core network to authenticate clients and subscriber subscriptions to aspects of the LCS.

The Uu interface may also be used for broadcast of information that may be used by the UE or stand-alone LMU for their LCS operations. This may, for example, include timing and code information about nearby Node-B transmissions that may assist the UE or LMU in making their measurements.

The Uu interface may also pass messages relating to changes or reporting of the data associated with the Location System Operations Function (LSOF) in the UE or the remote LMU.

UTRAN Stage 2 specification 25.305 [1] specifies LCS signaling over the Uu interface.

7.4 MAP Interfaces

The MAP interfaces defined for GSM LCS should be re-used as much as possible in UMTS.

There are two MAP interfaces in the UMTS Location Services:

– Interface between GMLC and HLR (Lh interface).

This interface is used by the GMLC to request the address of the visited MSC or 3G-SGSN for a particular target UE whose location has been requested.

– Interface between GMLC – MSC (Lg interface).

This interface is used by the GMLC to convey a location request to the MSC currently serving a particular target UE whose location was requested. The interface is used by the MSC to return location results to the GMLC.

The following MAP services are defined for GSM LCS and should be re-used for UMTS LCS:

– MAP-SEND-ROUTING-INFO-FOR-LCS Service.

This service is used between the GMLC and the HLR to retrieve the routing information needed for routing a location service request to the servicing 3G-VMSC.

– MAP-PROVIDE-SUBSCRIBER-LOCATION Service.

This service is used by a GMLC to request the location of a target UE from the visited MSC at any time.

– MAP-SUBSCRIBER-LOCATION-REPORT Service.

This service is used by a 3G-VMSC to provide the location of a target UE to a GMLC when a request for location is either implicitly administered or made at some earlier time.