9.1.4 CS-MT-LR and PS-MT-LR for a previously obtained location estimate

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

Every time the location estimate of a target UE subscriber is returned by the RAN to the VMSC, MSC Server or SGSN, the corresponding entity may store the location estimate together with a time stamp. The MSC/MSC server may store this information in the subscriber’s MSC server record. Also when the location estimate of a target UE subscriber is returned to the H-GMLC, the H-GMLC may store the location estimate together with the age in the subscriber’s record.

The time stamp is the time at which the location estimate is stored at the corresponding entity i.e. after the RAN returns the location estimate to the VMSC, MSC Server or SGSN. The time stamp indicates the "age" of the location estimate.

9.1.4.1 Initial Location

In the context of an originating emergency call the location estimate and the associated time stamp at the commencement of the call set-up is referred to as "initial location".

9.1.4.2 Current Location

After a location attempt has successfully delivered a location estimate and its associated time stamp, the location estimate and time stamp is referred to as the "current location" at that point in time.

9.1.4.3 Last known Location

Depending on national regulations, the current location estimate and its associated time stamp may be stored in MSC/VLR, MSC Server, SGSN, or in H-GMLC and until replaced by a later location estimate and a new time stamp is referred to as the "last known location". The last known location may be distinct from the initial location – i.e. more recent.

9.1.4.4 Security and Privacy

The collection and/or the release of the last known and initial location estimate of the target UE may not be allowed by national option. The handling of security and privacy of the target UE with regard to returning the last known or initial location estimate of the target UE shall be the same as when the target UE is reachable for positioning. (i.e. the requesting LCS client is authorized and the privacy of the target UE is secured before the VMSC/MSC server check the MSC server status of the target UE (i.e. whether the UE is marked as attached or detached in the MSC server). A similar status check apply for SGSN and MSC Server.

9.1.4.5 Failing to locate the target UE

In case of a "Detached" or "Not Reachable" target UE, the last known location and a time stamp stored at the VLR, MSC Server or SGSN, may be returned to a LCS client requesting location information if the LCS client specifically requested the current or last known location. This does not apply to a value added LCS client where the target UE subscribes to notification of the location request: if the notification cannot be performed, the VMSC, MSC Server or SGSN shall reject the location request.

NOTE: Due to CAMEL, the MSC/MSC server/VLR may already be storing other location information parameters like location number, service area identity and MSC server number in the subscriber’s MSC server record.

When a request for location information is received at the VMSC, MSC Server or SGSN, the request shall indicate whether the "last known location of the target UE" should be returned in case of a "detached" or "not reachable" target UE.

If the VLR, MSC Server or SGSN has a valid copy of the subscriber’s permanent data and the target UE’s privacy settings are such that positioning is allowed, then the following two cases can occur.

9.1.4.5.1 Target UE is "Not Reachable"

If the target UE is marked as "attached" in the VLR, MSC Server or SGSN, the corresponding entity orders paging of the target UE. If paging fails, due to target UE being "not reachable" then the corresponding VMSC, MSC Server or SGSN shall check whether the LCS client has requested "last known location" in case of "not reachable" target UE.

If such a request exists and notification to the target UE does not apply for a value added LCS client, the VMSC, MSC Server or SGSN shall include the last known location together with the time stamp available in its response to the request for location information.

An indicator of "last known location" returned shall be marked at the CDR at VMSC, MSC Server or SGSN correspondingly.

9.1.4.5.2 Target UE is "Detached"

If the target UE is marked as "detached" in the VLR, MSC Server or SGSN, the corresponding entity shall check whether the LCS client has requested "last known location" in case of "detached" target UE.

If such a request exists and notification to the target UE does not apply for a value added LCS client, the VMSC, MSC Server or SGSN includes the "last known location" together with the time stamp available in its response to the request for location information.

An indicator of "last known location" returned shall be marked at the CDR at VMSC, MSC Server or SGSN.

9.1.4.5.3 Target UE is Reachable but Positioning Fails

If the target UE is reachable (e.g. paging succeeds), but the VMSC, MSC Server or SGSN is unable to obtain a current location estimate, then the corresponding entity shall check whether the LCS client has requested "last known location".

If such a request exists and notification to the target UE either does not apply or was successfully executed for a value added LCS client, the VMSC, MSC Server or SGSN includes the "last known location" together with the time stamp available in its response to the request for location information. An indicator of "last known location" returned shall be marked at the CDR at VMSC.

9.1.4.5.4 MSC Server or SGSN Target UE is "Purged"

If the target UE is marked as "Purged" in HLR/HSS, then an indication "Absent Subscriber" is returned to the GMLC.