9.1.3 CS-MT-LR without HLR Query

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

Figure 9.3 illustrates current or last known location requests for an emergency services call, where an emergency services client (i.e., a Public Safety Answering Point) identifies the target UE and the serving GMLC using correlation information that were previously provided to it by the VMSC. In North America, this correlation information is provided by either an NA-ESRK, or an MSISDN and NA-ESRD. In E.U. it is provided through the ISUP/BICC IAM message with location number parameter set to MSC number and the calling party number parameter set to MSISDN. The signalling used to provide the correlation information to the PSAP is out of scope of this TS, but is presumed to occur on the signalling for the call. This allows the requesting V-GMLC to request location from the VMSC without first querying the home HLR of the target UE. This scenario therefore supports location of emergency callers from roamers or SIM-less emergency calls, or non-registered (U)SIM emergency calls, and requires that the initial location, as well as UE and VMSC identifying information had been pushed to the GMLC as per 9.1.5 (or 9.1.5.A for North America). In North America, additional requirements are found in [32].

Figure 9.3: Positioning for a Emergency Services MT-LR without HLR Query

1) Same as step 1 in figure 9.1 but with the LCS client (PSAP) identifying first the target UE and the serving V-GMLC by previously supplied correlation information for the emergency call.

2) The GMLC may determine the VMSC from correlation information received from the PSAP, or from stored information for the target UE (e.g. from a prior location estimate delivery from the VMSC/MSC server). In North America, the GMLC determines the VMSC using the NA-ESRK or NA-ESRD – with use of the NA-ESRK taking priority over that of the NA‑ESRD. The MAP_PROVIDE_SUBSCRIBER_LOCATION message sent to the VMSC carries the MSISDN and, if provided, the IMSI and IMEI for the target UE, as well as the required QoS and an indication of a location request from an emergency services client. The VMSC identifies the target UE using the IMSI or MSISDN and, if provided, the IMEI. In case of a SIM-less emergency call, or non-registered (U)SIM emergency call, the IMEI shall be always sent and the MSISDN may be populated with a non-dialable callback number as specified in clause 6.4.3.

3) The MSC verifies that UE privacy is overridden by the emergency services provider and that positioning is not prevented for other reasons (e.g. unreachable UE, inapplicable call type to the UE). The VMSC then sends a Location Request to the RAN, as for a normal MT-LR.

4) RAN performs positioning as for a normal CS-MT-LR.

5) RAN returns a location estimate to the VMSC as for a normal CS-MT-LR.

6) Same as step 9 for a normal CS-MT-LR.

7) Same as step 10 for a normal CS-MT-LR.