9.1.19 Deferred EPC-MT-LR for Periodic and Triggered Location

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

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

The procedures for periodic and triggered location for EPC services support instigation and cancellation of location reporting at periodic intervals or whenever some other trigger event is detected by the UE. The supported trigger events comprise an area event (where a UE enters, leaves or remains within a predefined area) and a motion event. In this version of the specification, only one type of reporting may be included in any request from among periodic, area event and motion event. In the case of the area event, a target area can be defined by a geographical area, PLMN identity, country code or geopolitical name. Details of the target area are contained in the LCS Service Request message, see clause 5.5.1. In the case of the motion event, motion corresponds to movement by the UE exceeding a linear distance threshold from a previous location. The procedure supports UE mobility between different serving MMEs and different serving PLMNs without interruption of event reporting.

9.1.19.1 Instigation and Reporting of Periodic and Triggered Location

Figure 9.1.19.1-1 illustrates the procedure used to instigate and perform event reporting for a periodic and triggered EPC-MT-LR request from an LCS client.

Figure 9.1.19.1-1: Deferred EPC-MT-LR procedure for Periodic and Triggered Location

1) The LCS Service Request provides the type of periodic or triggered location reporting being requested and associated parameters. For periodic location, the LCS Service Request includes the time interval between successive location reports, the total number of reports and may include location QoS. For area event reporting, the LCS Service Request includes details of the target area, whether the event to be reported is the UE being inside, entering into or leaving the target area, the duration of event reporting, the minimum and maximum time intervals between successive event reports, the maximum event sampling interval, whether location estimates shall be included in event reports (and associated location QoS), and whether only one location report is required or more than one. If the target area is expressed by a local coordinate system or a geopolitical name, the R-GMLC shall convert the target area to a geographical area expressed by a shape as defined in TS 23.032 [11]. For motion event reporting, the LCS Service Request includes the threshold linear distance, the duration of event reporting, the minimum and maximum time intervals between successive event reports, the maximum event sampling interval, whether location estimates shall be included in event reports (and associated location QoS), and whether only one location report is required or more than one.

2) LCS service request handling is performed between GMLCs as described in clause 9.1.1. The information received by the R-GMLC is transferred to the H-GMLC. The H-GMLC should record the received information and relevant parameters. The H-GMLC assigns an LDR reference number to the LCS Service request and an optional list of reporting PLMNs (which should include the serving PLMN), then transfers the information to the V-GMLC, including the LDR reference number, the H-GMLC address and any list of reporting PLMNs.

3) In case area event reporting is requested, if the target area is defined by a shape in TS 23.032 [11], the V-GMLC converts the target area into a corresponding list of cell identities and/or tracking areas. If the V-GMLC cannot convert the entire target area into network identities, it shall reject the request and send an LCS service response to the H-GMLC with the appropriate error cause. The V-GMLC then conveys the location request to the MME in a Provide Subscriber Location request including details of the events to be reported, the LDR reference number, the H-GMLC address and any list of reporting PLMNs.

4) The MME verifies the UE capabilities with regard to the support of location service related call independent supplementary services (e.g. notification for LCS). If either the UE does not support location service related call independent supplementary services or the MME does not support the deferred location request for periodic and triggered location (for temporary or permanent reasons), a Provide Subscriber Location error response shall be returned with a suitable error cause. Otherwise, the MME returns a Provide Subscriber Location Ack. to confirm that the request has been accepted by the MME.

NOTE 1: There is no UE capability information directly indicating support of a deferred periodic and triggered location request. However, if the UE supports at least one location service related call independent supplementary service (such as notification for LCS), the MME can assume support for deferred periodic and triggered location. If the UE does not recognize the request in step 9, it may return a Facility Rejected indication in step 10 (as defined in TS 24.008 [24]) to the MME in which case, the MME would terminate the request by instigating steps 19-24 with an appropriate error cause in the Subscriber Location Report sent at step 19.

5) to 7) The V-GMLC returns the LCS Service Response via the H-GMLC and R-GMLC to the LCS Client to notify whether the periodic and triggered location request was accepted or not. When the H-GMLC returns the LCS Service Response to the R-GMLC, the LDR reference number assigned by the H-GMLC shall be included, and the R-GMLC may transfer the LDR reference number, or another reference number assigned by the R-GMLC, to the LCS Client in the LCS Service Response.

NOTE 2: The LCS Service Response does not confirm that location reporting was activated in the UE or that the UE will necessarily be able to support the request. However, the response does confirm the capability and intent to support the request on the network side and may be useful to the LCS client when a response from the UE is delayed due to the UE being temporarily unreachable (e.g. if in PSM).

8) If the UE is currently not reachable (e.g. when in PSM), the MME waits until the UE again becomes reachable. When the UE is reachable, if the UE is in ECM-IDLE state, the MME performs paging, authentication and ciphering. If privacy notification/verification was requested and the UE supports location service related call independent supplementary services, the MME sends an LCS Location Notification Invoke message to the target UE with a location type indicating activation of a deferred location request, a deferred location event type indicating the type of event (i.e. entering into area, leaving from area, being inside area, periodic or motion) and an indication as to whether privacy verification is required. LCS Location Notification is further specified in clause 9.1.15. If privacy verification was requested, the UE returns an LCS Location Notification Return Result to the MME indicating whether permission is granted or denied. If the UE denies permission or does not return a response when a response is required, the MME terminates the request as described for step 11. If the UE changes serving MME before becoming reachable from the MME, the MME returns a Subscriber Location Report to the V-GMLC indicating a change of MME and including the new MME address if available. The V-GMLC may then forward the error to the LCS client via the H-GMLC and R-GMLC or repeat step 3 to transfer the periodic and triggered location request to the new MME if provided. In this case, when step 4 recurs, the V-GMLC does not repeat steps 5-7 as the LCS client was already informed of network acceptance of the request.

9) The MME sends an LCS Periodic-Triggered Event Invoke to the UE carrying all of the event related information received from the V-GMLC, the LDR reference number, the H-GMLC address, the list of reporting PLMNs if provided and any requested QoS in the case that location estimates are required.

10) If the UE supports periodic and triggered location according to the request received in step 9 and currently has resources to service the request, the UE sends an acknowledgement to the MME. Otherwise, the UE sends a return error response to the MME with a suitable error cause.

11) If the UE cannot support the periodic and triggered location request, a Subscriber Location Report shall be returned to the V-GMLC with a suitable error cause and including the LDR reference number and H-GMLC address. Otherwise, if the UE confirms support of the periodic and triggered location request, a Subscriber Location Report shall be returned to the V-GMLC indicating that event reporting was activated in the UE and including the LDR reference number and H-GMLC address. If location estimates are required for subsequent event reports, the MME should obtain the current UE location as in steps 15-17 and include the location estimate in the Subscriber Location Report. The V-GMLC returns an LCS Service Response via the H-GMLC and R-GMLC to the LCS Client to notify whether the periodic and triggered location request was activated in the UE. When the H-GMLC returns the LCS Service Response to the R-GMLC, the LDR reference number assigned by the H-GMLC and H-GMLC address shall be included, and the R GMLC may transfer the LDR reference number to the LCS Client in the LCS Service Response. The V-GMLC, H-GMLC and/or R-GMLC may record charging information for the request. Following step 11, the MME and V-GMLC may release all resources for the request including any state information.

NOTE 3: The LCS Service Response with an activation indication confirms to the LCS client that event reporting has started in the UE.

12) For the area event or motion event, the UE monitors the requested event at intervals equal to or less than the maximum event sampling interval. An event trigger is detected by the UE when any of the following occur: (i) a requested area event or motion event has been detected and the minimum reporting time interval has elapsed since the last report (if this is not the first event report); (ii) a requested periodic location event has occurred; or (iii) the maximum reporting time for an area event or motion event has expired. When an event trigger is detected, the UE proceeds to step 13 once the UE can register via E-UTRAN access with a PLMN in the list of reporting PLMNs received at step 9 or with the original serving PLMN if no list of reporting PLMNs was provided or if the UE does not support the list of reporting PLMNs. If the UE cannot register with a permitted PLMN, the UE waits until a permitted PLMN can be accessed in order to report the event, or for the periodic and triggered location request to terminate due to cancellation by the LCS client, cancellation by the UE or expiration of the allowed duration.

NOTE 4: If the UE uses a different serving PLMN to report occurrence of the area event, the UE still continues to use the target area provided by the original serving PLMN which contains cell IDs and/or TAs for the original serving PLMN.

NOTE 5: The restriction to use only permitted PLMNs does not affect PLMN selection.

13) If the UE is not using Control Plane CIOT EPS Optimisation and if the UE is in ECM-IDLE state, the UE performs a UE triggered service request or connection resume as defined in TS 23.401 [41] in order to obtain a signalling connection to a serving MME.

If the UE is using Control Plane CIoT EPS Optimisation, procedures for Mobile Originated Data Transport in Control Plane CIoT EPS optimisation as defined in TS 23.401 [41] are performed by the UE to establish a signalling connection with the MME.

NOTE 6: The MME and V-GMLC for steps 13 to 24 may be different to the MME and V-GMLC for steps 1 to 11.

14) The UE sends an LCS MO-LR Invoke to the MME indicating an event report for a deferred periodic and triggered location request. The message includes the type of event trigger being reported (e.g. whether a normal event or expiration of the maximum reporting interval), the LDR reference number, H-GMLC address and whether a location estimate is required. When a location estimate is required (e.g. for a periodic location event or for an area event or motion event if requested by the LCS client), the UE shall include any QoS received in step 9 and a location estimate if a location estimate is currently available. The UE shall also indicate whether the periodic and triggered location request is now terminated in the UE (e.g. due to expiration of the reporting duration or because only one event report was requested).

NOTE 7: Provision of a location estimate when requested also applies to the trigger event corresponding to expiration of the maximum reporting interval for an area event or motion event.

15-17) If the UE indicates that a location estimate is required in step 14, the MME shall instigate location of the UE as described in steps 6-8 of clause 9.1.15 if a location estimate is not provided by the UE in step 14 and may optionally instigate location of the UE if a location estimate is provided by the UE in step 14. In the latter case, the location estimate provided by the UE shall be included in the location request sent to the E-SMLC in step 15.

18) The MME sends an MO-LR Return Result to the UE confirming that the event report will be sent. If the MME is unable to send the event report (e.g. because this capability is not supported by the MME), an MO-LR return error is returned to the UE. The UE may terminate event reporting after an implementation defined number of MO-LR return errors are received.

19) The MME selects a V-GMLC in the same network and sends a Subscriber Location Report to the V-GMLC with an indication of the type of event being reported, the LDR reference number, the H-GMLC address, whether the location request is now terminated in the UE, any location estimate provided in step 13 or obtained in steps 14-16 and information on positioning methods used for the location estimate. The MME shall also include the UE IMSI.

20) The V-GMLC sends an acknowledgement to the MME and the MME may record charging information.

21) The V-GMLC forwards the information received in step 19 to the H-GMLC. The V-GMLC may record charging information.

22) The H-GMLC identifies the location request to which the message received in step 21 applies using the LDR reference number and IMSI. The H-GMLC may perform a privacy check as described in clause 9.1.1.

23) The H-GMLC forwards the information received from the V-GMLC in an LCS Service Response to the R-GMLC. If the UE indicates termination of the location request, the periodic location request shall be completed in the H-GMLC. The H-GMLC may record charging information.

24) The R-GMLC transfers the event report and any included location estimate to the LCS Client. If the UE indicates termination of the location request, the location request shall be completed in the R-GMLC. The R-GMLC may record charging information.

25) If the UE did not terminate the location request following step 18, the UE continues to monitor for the requested event as in step 12 and reports each occurrence of the requested event as in steps 13-24 until expiration of the requested duration or until the UE terminates reporting for other reasons.

9.1.19.2 LCS Client cancellation of a Deferred Location Request for Periodic and Triggered Location

Figure 9.1.19.2-1 illustrates the procedure for cancelling a Deferred Location Request for periodic and triggered location when cancellation is requested by the LCS Client.

Figure 9.1.19.2-1: LCS Client cancellation of a Deferred MT-LR for Periodic and Triggered Location

1) The LCS Client requests the cancellation of a previously requested Deferred Location Request for periodic and triggered location. The LDR (or other) reference number that was included in the previous LCS Service Response sent by the R-GMLC shall be included in the request to indicate which outstanding LDR should be cancelled.

2) The R-GMLC sends the cancellation request to the H-GMLC, including the LDR reference number. The R GMLC may itself initiate the cancellation, e.g. whenever the R-GMLC infers from the absence of location reports for a long period that the service may have been terminated by the UE.

3) The H-GMLC may send a SEND_ROUTING_INFO_FOR_LCS message to the home HLR/HSS of the UE with the IMSI or MSISDN of this UE. This may be needed if the UE is no longer served by the original V PLMN or by the original MME.

4) The HLR/HSS returns the current serving MME for the UE and the V-GMLC address.

5) The H-GMLC forwards the LCS Cancel Service Request to the V-GMLC with the LDR reference number received from the R-GMLC, the H-GMLC address and the serving MME address (e.g. received from the HLR/HSS). The H-GMLC may itself initiate the cancellation procedure, when the UE’s privacy profile stored in the H-GMLC or in the PPR was changed in a manner that no longer allows the LCS Client to receive event and location reports for the UE.

NOTE: The H-GMLC shall know that the UE subscriber’s privacy profile has been changed in the PPR when the LCS Privacy Profile Update has been sent from PPR to H-GMLC as described in clause 9.1.1.2.

6) The V-GMLC sends the Provide Subscriber Location request to the serving MME, indicating a cancellation of a deferred location request for periodic and triggered location and including the LDR reference number specified by the LCS Client in the LCS Cancel Service Request and the H-GMLC address received from the H-GMLC. The V-GMLC shall transfer the location cancellation even when the V-GMLC was not involved in establishing the location request.

7) If the UE is currently not reachable (e.g. during an eDRX cycle or when in PSM), the MME waits until the UE becomes reachable. When the UE is reachable, if the UE is in ECM-IDLE state, the MME performs paging, authentication and ciphering.

8) The MME sends an LCS Periodic Location Cancellation request, including the LDR reference number and H-GMLC address, to the UE.

9) The UE stops the periodic and triggered event reporting and returns an LCS Periodic Location cancellation ack. to the MME. Return of an LCS Periodic Location cancellation ack. shall apply even when the UE has no knowledge of the location procedure being cancelled (e.g. if the UE was powered off during the procedure).

10) The MME sends the cancellation acknowledgement to the V-GMLC in a Provide Subscriber Location Ack, with the LDR reference number and the H-GMLC address. If the MME was unable to perform steps 7-8 (e.g. due to a change of MME or PLMN by the UE), the MME returns a Provide Subscriber Location error response with a suitable error cause. The V-GMLC then returns the error to the H-GMLC which may retry the cancellation with a different MME or different PLMN if applicable.

11) The V-GMLC sends an LCS Cancel Service Response to the H-GMLC with the LDR reference number and the H GMLC address.

12) The H-GMLC sends an LCS Cancel Service Response to the R-GMLC with the LDR reference number.

13) The R-GMLC sends an LCS Cancel Service Response to the LCS Client.

9.1.19.3 UE cancellation of a Deferred Location Request for Periodic and Triggered Location

Figure 9.1.19.3-1 illustrates the procedure for cancelling the Deferred Location Request for the periodic and triggered location event when cancellation is requested by the UE. If a network entity (e.g. H-GMLC, V-GMLC, MME) cancels the Deferred Location Request, the procedure in clause 9.1.19.2 for LCS Client cancellation shall be used to cancel towards the UE and the procedure in this clause shall be used to cancel towards the LCS Client.

Figure 9.1.19.3-1: UE cancellation of a Deferred MT-LR for Periodic and Triggered Location

1) The UE waits until the UE is registered or can register via E-UTRAN access with a PLMN in the list of reporting PLMNs received at step 9 of the procedure in clause 9.1.19.1 or with the original serving PLMN for the procedure in clause 9.1.19.1 if no list of reporting PLMNs was provided or if the UE does not support the list of reporting PLMNs.

If the UE is not using Control Plane CIoT EPS Optimisation and if the UE is in ECM-IDLE state, the UE performs a UE triggered service request or connection resume as defined in TS 23.401 [41] in order to obtain a signalling connection to a serving MME.

2) The UE sends an LCS MO-LR Invoke to the serving MME for cancellation of a deferred MR-LR for periodic and triggered location. This message includes the H-GMLC address, a termination cause (e.g. subscriber terminates the procedure) and the LDR Reference Number.

3) The cancellation request shall be transferred from the MME to a V-GMLC and shall include the H-GMLC address, LDR reference number and IMSI of the UE.

4) to 6) The cancellation request shall be transferred to the H GMLC, R GMLC serving the LCS client and finally to the LCS client.

7) to 10) The response transferred back to the MME acknowledges the cancellation.

11) The MME returns the acknowledgment to the UE in a LCS MO-LR Return Result message.