9.1.14 IW-MT-LR Procedure without HLR/HSS or AAA Query

23.2713GPPFunctional stage 2 description of Location Services (LCS)Release 17TS

This procedure is applicable to the I-WLAN defined in TS 23.234 [52] and it is no longer maintained.

Figure 9.17 illustrates current or last known location requests for an emergency services call, where an emergency services client (i.e. a Public Safety Answering Point) requests updated location information for the target UE. In order to support location of emergency call s from UICC-less terminals, TS 23.167 [36a] specifies that the IMS core shall push information identifying the terminal to the PSAP and GMLC during establishment of the emergency call.

NOTE 1: In some regions, based on regional specifications, the GMLC may use correlation information that was previously provided to it by the IMS Core to identify the target UE.

The IMS core also sends the correlation information to the PSAP during the call establishment as described in TS 23.167 [36a]. Using the correlation key the PSAP may request the initial or updated location information from the GMLC. The management of this regional correlation information (e.g. ESQK in North America) and support of the Le interface to the external LCS Client may be handled by a separate functional entity from the GMLC, e.g. a RDF as defined in TS 23.167 [36a].

Figure 9.17: IW-MT-LR without an HLR/HSS or AAA Query

1. The WLAN UE selects a WLAN AN and establishes the WLAN connection and may be authenticated in I-WLAN. The tunnel is established between the WLAN UE and a PDG in PLMN.

2. The WLAN UE establishes an emergency services call as described in TS 23.167 [36a]. The UE determines its own location if possible. The UE may include the identifier of access node (e.g., MAC address of the AP), if available, as location identifier in the session request and possibly other readily available location information, e.g. GPS based coordinates or the street address of the UE or the AP as provided by the user of the UE. If the UE is not able to determine its own location, the UE may, if capable, request the location information from the IP‑CAN or SLP. The case when the UE requests its own location information or enhanced location information from the SLP using OMA-SUPL is described in clause 9.2.5. The IP-CAN may return a representation of the location information to the UE. During this step, the IMS core may push the WLAN UE’s identification and the location information provided by the UE to the LRF (GMLC) along with correlation information, if applicable. The GMLC may record this information but in some regions only for the duration of the call as the case may be. The correlation information may be regionally specific (e.g. as is the case for support of location for an emergency call in the CS domain in clause 9.1.3). The IMS core shall also send the correlation information to the PSAP/ emergency centre during the call establishment as specified in TS 23.167 [36a].

NOTE 2: The mechanism used by the UE to obtain location information from the I‑WLAN IP‑CAN is out of scope. One method that could be used is the mechanism defined by IEEE 802.11k Task Group for carrying location information (per RFC 3825) from one IEEE 802.11 station/AP to another IEEE 802.11 station/AP.

3. An external LCS client associated with the emergency centre PSAP sends a location request to the GMLC for the initial location or an updated location for the WLAN UE. The request may include the address and the identification of the WLAN UE and in some regions may include correlation information that enables the GMLC to associate the request with the information stored in step 2.

4. If initial location was requested the procedure continues from step 5. If updated location was requested the GMLC initiates a positioning procedure where either the UE or GMLC determines the position of the UE. GMLC/SLP shall request the UE to establish a so called user plane connection with the GMLC/SLP and use the OMA SUPL mechanism specified by OMA (OMA AD SUPL [38], OMA TS ULP [39]) to transport location related assistance data and location information between the UE and GMLC/SLP. The UE may send the identifier of the access node (e.g. MAC address of the AP) to the GMLC and GMLC, possibly using an external database, maps this location identifier to the corresponding geographical information, e.g. coordinates or street address. GMLC may return this geographical information to the UE.

NOTE 3: The location information obtained based on the mapping of an identifier of access node (e.g. MAC address of the AP) to location information stored in a database may not be correct, e.g. the location of the AP might be changed without any updates to the database.

5. GMLC sends the initial location information, if so requested, or the updated location information obtained in step 4 to the external LCS client.