6.7 Low Power Periodic and Triggered 5GC-MT-LR Procedures

23.2733GPP5G System (5GS) Location Services (LCS)Release 18Stage 2TS

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

The low power periodic and triggered 5GC-MT-LR procedures may be used to support a request from an external LCS client or AF for deferred location for periodic or triggered location events. The procedures may be used as alternatives to the procedures in clause 6.3.1 and clause 6.4. If the procedures are used, cancellation of the reporting of location events is still supported using the procedures in clause 6.3.2 and clause 6.3.3.

6.7.1 Event Reporting with no change of LMF

Figure 6.7.1-1 summarizes the initiation and reporting of location events for a deferred 5GC-MT-LR procedure for Periodic or Triggered Location Events using low power event reporting. This procedure is only applicable to a UE with E-UTRA access to 5GC.

Figure 6.7.1-1: Low Power Periodic and Triggered 5GC-MT-LR Procedure with no change of LMF

1. Steps 1-23 for the deferred 5GC-MT-LR procedure for periodic or triggered location events in clause 6.3.1 are performed with the following exceptions.

– At step 14, the AMF includes an indication in the Nlmf_Location_DetermineLocation Request service operation that the UE supports and is allowed to use Control Plane CIoT 5GS Optimisation as described in clause 5.31.4 of TS 23.501 [18].

– At step 16, if the AMF indicates the UE supports and is allowed to use Control Plane CIoT 5GS Optimisation at step 14 and if the LMF decides to allow Control Plane CIoT 5GS Optimisation, the LMF includes an indication in the LCS Periodic-Triggered Invoke Request that the UE is allowed to use Control Plane CIoT 5GS Optimisation to send Event Reports. The LMF may also include criteria indicating when Control Plane CIoT 5GS Optimisation may be used to send Event Reports. The criteria may include a maximum duration for sending Event Reports using Control Plane CIoT 5GS Optimisation, a maximum number of consecutive Event Reports to be sent using Control Plane CIoT 5GS Optimisation or both.

NOTE 1: As part of negotiating 5G network behaviour during registration, a UE indicates in a Registration Request whether Control Plane CIoT 5GS Optimisation is supported for location event reporting. This indication may be passed to the LMF by the AMF at step 14 for clause 6.3.1.

2. The UE determines whether to report the event detected at step 22 in clause 6.3.1 using Control Plane CIoT 5GS Optimisation or using a NAS signalling connection. If the UE is currently in CM CONNECTED state or is not accessing E-UTRA connected to 5GC, the UE shall use a NAS signalling connection. Otherwise, the determination shall be based on criteria received from the LMF at step 14 in clause 6.3.1 when criteria are received. When the criteria include a maximum duration for sending event reports using Control Plane CIoT 5GS Optimisation, the UE shall report the event using a NAS signalling connection if the UE has not used a NAS signalling connection to report events during an immediately preceding time interval equal to the maximum duration. When the criteria include a maximum number of consecutive Event Reports to be sent using Control Plane CIoT 5GS Optimisation, the UE shall report the event using a NAS signalling connection if the UE has used Control Plane CIoT 5GS Optimisation to report each of the N previous events, where N equals the maximum number of consecutive Event Reports. In other cases, Control Plane CIoT 5GS Optimisation may be used to report the event if supported by the 3GPP access type. If use of a NAS signalling connection is determined, steps 24-31 for the procedure in clause 6.3.1 are performed and steps 3-11 below are skipped. If use of Control Plane CIoT 5GS Optimisation is determined, steps 3-11 below are performed.

3. If the UE and ng-eNB node both support EDT, the UE sends an RRCEarlyDataRequest message to the ng-eNB node and includes a NAS control plane service request.

Otherwise, the UE established an RRC connection with the ng-eNB node and sends the NAS control plane service request. The NAS control plane service request includes an event report message which includes the information described in step 25 in clause 6.3.1 (e.g. the type of event being reported and any location measurements or location estimate obtained at step 23 in clause 6.3.1). The control plane service request also includes the deferred routing identifier received in step 16 in clause 6.3.1. The UE also includes a NAS Release Assistance Indication (NAS RAI) in the NAS message. The NAS RAI indicates a single response is expected.

NOTE 2: Event reporting using Control Plane CIoT 5GS Optimisation requires a single Event report acknowledgment from the LMF.

4. The ng-eNB node forwards the NAS message to the AMF in an N2 Initial UE message and includes an "EDT Session" indication if EDT was used at step 3.

5. The AMF checks the integrity of the NAS message and deciphers its contents. The AMF then invokes an Namf_Communication_N1MessageNotify service operation to forward the event report to either the serving LMF or any suitable LMF as described for step 25 for clause 6.3.1. The AMF includes an indication of Control Plane CIoT 5GS Optimisation in the service operation and the serving cell ID.

6. The AMF returns a NAS Service Accept to the ng-eNB node which is encapsulated in an N2 Downlink NAS Transport message.

7. If EDT was used at step 3, the ng-eNB node establishes an RRC connection to the UE.

8. The ng-eNB node sends an RRC DL Information Transfer message to the UE and includes the NAS Service Accept message received in step 6.

9. The LMF invokes an Namf_Communication_N1N2MessageTransfer operation to return an acknowledgment for the event report as described for step 26 for clause 6.3.1.

10. The AMF forwards the acknowledgment to the ng-eNB node in a NAS DL NAS Transport message which is encapsulated in an N2 Downlink NAS Transport message. The AMF also includes an "end indication" in the N2 message.

NOTE 3: If the AMF determines more data or signalling may be pending for the UE, the AMF does not include the "end indication" at step 10 and step 12 below is not performed.

11. The ng-eNB node sends an RRC DL Information Transfer message to the UE and includes the NAS message received in step 10.

12. If the "end indication" was received in step 10, the ng-eNB node releases the RRC connection.

13. If a location estimate is needed for event reporting, the LMF determines the UE location using the location measurements and/or location estimate received in the event report at step 5 and/or the serving cell ID provided by the AMF at step 5.

NOTE 4: The LMF does not attempt to obtain additional location measurements from the UE or from the NG-RAN.

14. Steps 28-31 for clause 6.3.1 are performed to send the event report to the external client or AF and to continue event detection at the UE.

6.7.2 Event Reporting with change of LMF

Figure 6.7.2-1 shows a procedure to enable change of the serving LMF when a UE sends an event report as at steps 3 and 4 in clause 6.7.1.

Figure 6.7.2-1: Event Reporting with change of LMF

Precondition: Step 1 in clause 6.7.1 has already been performed and steps 2-11 in clause 6.7.1 may have been performed or repeated. A serving LMF is used and the current serving LMF is LMF1.

1. Steps 2-4 for Event Reporting for no change of LMF in clause 6.7.1 are performed with the following exceptions.

– At step 3, the NAS control plane service request includes a deferred routing identifier indicating LMF1.

2. Steps 3-8 for the LMF Change procedure in clause 6.4 are performed with the following exceptions.

– At step 4, the Namf_Communication_N1MessageNotify service operation includes an indication of Control Plane CIoT 5GS Optimisation.

– At step 6, the Nlmf_Location_LocationContextTransfer Request service operation includes an indication of Control Plane CIoT 5GS Optimisation and the serving cell ID.

3. Steps 7-10 for Event Reporting for no change of LMF in clause 6.7.1 are performed with LMF2 replacing the LMF in clause 6.7.1. The rest of the procedure in clause 6.7.1 then continues in step 11 with LMF2 retaining state information to enable support of subsequent event reports from the UE.

6.7.3 Event Reporting in RRC INACTIVE state for DL Positioning, RAT Independent Positioning or No Positioning

Figure 6.7.3-1 summarizes the initiation and reporting of location events for a deferred 5GC-MT-LR procedure for Periodic or Triggered Location Events when a UE is in RRC INACTIVE state and when DL positioning, RAT independent positioning or no positioning is used for event reporting. This procedure is only applicable to a UE with NR access to 5GC.

Figure 6.7.3-1: Low Power Periodic and Triggered 5GC-MT-LR Procedure in RRC INACTIVE state with DL Positioning, RAT Independent Positioning or No Positioning

1. Steps 1-21 for the deferred 5GC-MT-LR procedure for periodic or triggered location events in clause 6.3.1 are performed with the following differences.

– At step 16 in clause 6.3.1, the LMF indicates to the UE that DL positioning, RAT Independent positioning or no positioning will be used for subsequent location reporting events when the UE is in RRC INACTIVE state. If DL positioning or RAT independent positioning will be used, the LMF includes an LPP positioning message in the LCS Periodic-Triggered Invoke Request sent to the UE at step 16, where the LPP positioning message requests DL location measurements, RAT independent location measurements or a location estimate based on these location measurements. If no location of the UE is needed for event reporting or if a location based on a Cell ID will suffice for the location QoS, the LMF does not include an LPP positioning message in the LCS Periodic-Triggered Invoke Request sent to the UE at step 16.

NOTE 1: A deferred routing identifier indicating a default LMF cannot be included in the LCS Periodic-Triggered Location Invoke sent at step 16 in clause 6.3.1 because for event reporting at steps 5-11 below. the LMF needs to know which type of positioning was indicated at step 1 in order to correctly support these subsequent steps. However, a default LMF would not know which type of positioning had been indicated at step 1.

2. The UE enters RRC INACTIVE state some time before an event is detected at step 22 or step 31 in clause 6.3.1. If the UE is not in RRC INACTIVE state when an event is detected at step 22 or step 31 in clause 6.3.1, then the UE follows the procedure described for steps 22-31 in clause 6.3.1 to report the event to the LMF and to the LCS Client or AF.

NOTE 2: The LMF is not aware of whether the UE is in RRC INACTIVE state. This allows the LMF to follow the procedure described here or the procedure described in clause 6.3.1 for event reporting. With the procedure described here, a UE that was initially in RRC INACTIVE state can remain in RRC INACTIVE state after the procedure is complete. With the procedure in clause 6.3.1, a UE that was initially in RRC INACTIVE state could be moved into RRC CONNECTED state during the procedure in clause 6.3.1.

3. The UE monitors for and detects a trigger event as described for step 22 in clause 6.3.1.

4. If DL positioning or RAT independent positioning was indicated at step 1, the UE obtains the location measurements or location estimate requested in the LPP message received in step 1. If DL positioning or RAT independent positioning was not indicated at step 1, this step is skipped.

5. The UE sends an RRC Resume Request with small data transmission (SDT) to a receiving gNB node in the NG-RAN. The RRC Resume Request includes an RRC UL Information Transfer message containing an UL NAS TRANSPORT message that includes a supplementary services event report message. If DL positioning or RAT independent positioning was indicated at step 1, the UE includes an LPP positioning message in the supplementary services event report message that includes the location measurements or location estimate obtained at step 4. If DL positioning or RAT independent positioning was not indicated at step 1, the UE does not include an LPP positioning message in the supplementary services event report message. The event report message also includes other information described in step 25 in clause 6.3.1 (e.g. the type of event being reported). The UL NAS TRANSPORT message also include the deferred routing identifier received in step 16 in clause 6.3.1.

6. The receiving gNB node forwards the UL NAS TRANSPORT message to the serving AMF in an N2 Uplink NAS Transport message.

NOTE 3: If the receiving gNB node is not the anchor gNB node for the UE, the UL NAS TRANSPORT message may be forwarded to the serving AMF via the anchor gNB node.

7. The AMF checks the integrity of the NAS message and deciphers its contents. The AMF then invokes an Namf_Communication_N1MessageNotify service operation to forward the event report to the serving LMF as described for step 25 in clause 6.3.1.

8. The LMF invokes an Namf_Communication_N1N2MessageTransfer operation to return an acknowledgment for the event report as described for step 26 in clause 6.3.1.

NOTE 4: If there is a change of LMF according to clause 6.4, the acknowledgment includes a deferred routing identifier for the new LMF as described in clause 6.4.

9. The AMF forwards the acknowledgment to the receiving gNB node in a DL NAS TRANSPORT message which is encapsulated in an N2 Downlink NAS Transport message.

NOTE 5: If the receiving gNB node is not the anchor gNB node for the UE, the DL NAS TRANSPORT message may be forwarded to the receiving gNB node via the anchor gNB node.

10. The receiving gNB node sends a Subsequent DL SDT message to the UE and includes the NAS message received in step 10.

11. The receiving gNB node sends an RRC Release message to the UE to keep the UE in RRC INACTIVE state.

12. Following step 11, the UE remains in RRC INACTIVE state.

13. If a location estimate is needed for event reporting, the LMF determines the UE location using the location measurements or location estimate received at step 7 or a Cell ID provided by the AMF at step 7.

NOTE 6: The LMF does not attempt to obtain additional location measurements from the UE or from the NG-RAN.

14. Steps 28-31 for clause 6.3.1 are performed to send the event report to the LCS client or AF.

6.7.4 Event Reporting in RRC INACTIVE state for UL Positioning

Figure 6.7.4-1 summarizes the initiation and reporting of location events for a deferred 5GC-MT-LR procedure for Periodic or Triggered Location Events when a UE is in RRC INACTIVE state and when UL positioning is used for event reporting. This procedure is only applicable to a UE with NR access to 5GC.

Figure 6.7.4-1: Low Power Periodic and Triggered 5GC-MT-LR Procedure in RRC INACTIVE state with UL Positioning

1. Steps 1-21 for the deferred 5GC-MT-LR procedure for periodic or triggered location events in clause 6.3.1 are performed with the following differences.

– At step 16 in clause 6.3.1, the LMF indicates to the UE that UL positioning may be used for subsequent location reporting events when the UE is in RRC INACTIVE state by not including an LPP positioning message in the LCS Periodic-Triggered Invoke Request sent to the UE at step 16.

NOTE 1: A deferred routing identifier indicating a default LMF cannot be included in the LCS Periodic-Triggered Location Invoke sent at step 16 in clause 6.3.1 because for event reporting at steps 4-11 below. the LMF needs to know which type of positioning was indicated at step 1 in order to correctly support these subsequent steps. However, a default LMF would not know which type of positioning had been indicated at step 1.

3. The UE monitors for and detects a trigger event as described for step 22 in clause 6.3.1.

4. The UE sends an RRC Resume Request with small data transmission (SDT) to a receiving gNB node in the NG-RAN. The RRC Resume Request includes an RRC UL Information Transfer message containing an UL NAS TRANSPORT message that includes a supplementary services event report message. The UE does not include an LPP positioning message in the supplementary services event report message. The event report message includes other information described in step 25 in clause 6.3.1 (e.g. the type of event being reported). The UL NAS TRANSPORT message also includes the deferred routing identifier received in step 16 in clause 6.3.1.

5. The receiving gNB node forwards the UL NAS TRANSPORT message to the serving AMF in an N2 Uplink NAS Transport message.

NOTE 3: If the receiving gNB node is not the anchor gNB node for the UE, the UL NAS TRANSPORT message may be forwarded to the serving AMF via the anchor gNB node.

6. The AMF checks the integrity of the NAS message and deciphers its contents. The AMF then invokes an Namf_Communication_N1MessageNotify service operation to forward the event report to the serving LMF as described for step 25 in clause 6.3.1.

7. The LMF uses the Network Assisted Positioning Procedure in clause 6.11.2 to request the receiving gNB node to provide an UL configuration to the UE at step 11. The receiving gNB node then determines an UL Configuration to be used later at step 11 and indicates this to the LMF. The LMF also uses the Non-UE Associated Network Assistance Data procedure in clause 6.11.3 to request UL location measurements of the UE by NG-RAN gNB nodes.

NOTE 4: Because the UE is in RRC INACTIVE state and thus in CM CONNECTED state, step 2 of the Network Assisted Positioning Procedure in clause 6.11.2 whereby the AMF performs a Network Triggered Service Request will not be performed. This avoids a transition of the UE into RRC CONNECTED state.

8. The LMF invokes an Namf_Communication_N1N2MessageTransfer operation to return an acknowledgment for the event report as described for step 26 in clause 6.3.1.

NOTE 5: If there is a change of LMF according to clause 6.4, the acknowledgment includes a deferred routing identifier for the new LMF as described in clause 6.4.

9. The AMF forwards the acknowledgment to the receiving gNB node in a DL NAS TRANSPORT message which is encapsulated in an N2 Downlink NAS Transport message.

NOTE 6: If the receiving gNB node is not the anchor gNB node for the UE, the DL NAS TRANSPORT message may be forwarded to the receiving gNB node via the anchor gNB node.

10. The receiving gNB node sends a Subsequent DL SDT message to the UE and includes the NAS message received in step 10.

11. The receiving gNB node sends an RRC Release message to the UE to keep the UE in RRC INACTIVE state and includes the UL Configuration determined at step 7.

12. The UE transmits UL positioning signals according to the UL Configuration received at step 11. The NG-RAN gNB nodes that were requested to obtain UL location measurements at step 7 obtain the UL location measurements of the UL positioning signals transmitted by the UE.

13. The NG-RAN gNB nodes transfer the UL location measurements obtained at step 12 to the LMF according to the Non-UE Associated Network Assistance Data Procedure in clause 6.11.3.

14. Following step 13, the UE remains in RRC INACTIVE state.

15. The LMF determines the UE location using the UL location measurements received at step 13.

NOTE 7: The LMF does not attempt to obtain additional location measurements from the UE or from the NG-RAN.

16. Steps 28-31 in clause 6.3.1 are performed to send the event report to the LCS client or AF.

6.7.5 Event Reporting in RRC INACTIVE state for UL+DL Positioning

Figure 6.7.5-1 summarizes the initiation and reporting of location events for a deferred 5GC-MT-LR procedure for Periodic or Triggered Location Events when a UE is in RRC INACTIVE state and when UL-DL positioning is used for event reporting. This procedure is only applicable to a UE with NR access to 5GC.

Figure 6.7.5-1: Low Power Periodic and Triggered 5GC-MT-LR Procedure in RRC INACTIVE state with UL+DL Positioning

1. Steps 1-21 for the deferred 5GC-MT-LR procedure for periodic or triggered location events in clause 6.3.1 are performed with the following differences.

– At step 16 in clause 6.3.1, the LMF indicates to the UE that UL+DL positioning will be used for subsequent location reporting events when the UE is in RRC INACTIVE state by including an LPP positioning message in the LCS Periodic-Triggered Invoke Request sent to the UE at step 16, where the LPP positioning message identifies an UL-DL positioning method and requests DL location measurements for this positioning method. The LMF also includes a deferred routing identifier in the LCS Periodic-Triggered Location Invoke which is an identification of the LMF.

NOTE 1: A deferred routing identifier indicating a default LMF cannot be included in the LCS Periodic-Triggered Location Invoke sent at step 16 in clause 6.3.1 because for event reporting at steps 4-20 below. the LMF needs to know which type of positioning was indicated at step 1 in order to correctly support these subsequent steps. However, a default LMF would not know which type of positioning had been indicated at step 1.

3. The UE monitors for and detects a trigger event as described for step 22 in clause 6.3.1.

4. The UE sends an RRC Resume Request with small data transmission (SDT) to a receiving gNB node in the NG-RAN. The RRC Resume Request includes an RRC UL Information Transfer message containing an UL NAS TRANSPORT message that includes a supplementary services event report message. The UE includes an LPP positioning message in the supplementary services event report message that includes a request for an UL Configuration to support the UL+DL positioning method indicated to the UE at step 1. The event report message also includes other information described in step 25 in clause 6.3.1 (e.g. the type of event being reported). The UL NAS TRANSPORT message also includes the deferred routing identifier received in step 16 in clause 6.3.1.

5. The receiving gNB node forwards the UL NAS TRANSPORT message to the serving AMF in an N2 Uplink NAS Transport message.

NOTE 3: If the receiving gNB node is not the anchor gNB node for the UE, the UL NAS TRANSPORT message may be forwarded to the serving AMF via the anchor gNB node.

8. The LMF invokes an Namf_Communication_N1N2MessageTransfer operation to return an acknowledgment for the event report as described for step 26 in clause 6.3.1.

NOTE 5: If there is a change of LMF according to clause 6.4, the acknowledgment includes a deferred routing identifier for the new LMF as described in clause 6.4.

9. The AMF forwards the acknowledgment to the receiving gNB node in a DL NAS TRANSPORT message which is encapsulated in an N2 Downlink NAS Transport message.

NOTE 6: If the receiving gNB node is not the anchor gNB node for the UE, the DL NAS TRANSPORT message may be forwarded to the receiving gNB node via the anchor gNB node.

10. The receiving gNB node sends a Subsequent DL SDT message to the UE and includes the NAS message received in step 9.

11. The receiving gNB node sends an RRC Release message to the UE to keep the UE in RRC INACTIVE state and includes the UL Configuration determined at step 7.

12. The UE transmits UL positioning signals according to the UL Configuration received at step 11. The UE also obtains DL location measurements as requested at step 1. The NG-RAN gNB nodes that were requested to obtain UL location measurements at step 7 obtain the UL location measurements of the UL positioning signals transmitted by the UE.

13. The NG-RAN gNB nodes transfer the UL location measurements obtained at step 12 to the LMF according to the Non-UE Associated Network Assistance Data Procedure in clause 6.11.3.

14. The UE sends an RRC Resume Request with small data transmission to the receiving gNB node. The RRC Resume Request includes an RRC UL Information Transfer message containing an UL NAS TRANSPORT message that includes a supplementary services event report message. The event report message indicates that this is a second event report associated with the first event report sent at step 4 and includes an LPP positioning message that includes the DL location measurements obtained at step 12. The UL NAS TRANSPORT message also includes the deferred routing identifier received in either step 16 in clause 6.3.1 or step 10 in this procedure if there was a change of LMF.

NOTE 7: The LMF can be aware that UL+DL positioning is used from receipt at step 6 of the LPP positioning message in the supplementary services event report message that includes a request for an UL Configuration to support the UL+DL positioning method indicated to the UE at step 1. The LMF can thus expect to receive the second event report at step 14.

15. The receiving gNB node forwards the UL NAS TRANSPORT message to the serving AMF in an N2 Uplink NAS Transport message.

NOTE 8: If the receiving gNB node is not the anchor gNB node for the UE, the UL NAS TRANSPORT message may be forwarded to the serving AMF via the anchor gNB node.

16. The AMF checks the integrity of the NAS message and deciphers its contents. The AMF then invokes an Namf_Communication_N1MessageNotify service operation to forward the event report to the serving LMF as described for step 25 in clause 6.3.1.

17. The LMF invokes an Namf_Communication_N1N2MessageTransfer operation to return an acknowledgment for the event report as described for step 26 in clause 6.3.1.

18. The AMF forwards the acknowledgment to the receiving gNB node in a DL NAS TRANSPORT message which is encapsulated in an N2 Downlink NAS Transport message.

NOTE 9: If the receiving gNB node is not the anchor gNB node for the UE, the DL NAS TRANSPORT message may be forwarded to the receiving gNB node via the anchor gNB node.

19. The receiving gNB node sends a Subsequent DL SDT message to the UE and includes the NAS message received in step 18.

20. The receiving gNB node sends an RRC Release message to the UE to keep the UE in RRC INACTIVE state.

21. Following step 20, the UE remains in RRC INACTIVE state.

22. The LMF determines the UE location using the UL location measurements received at step 13 and the DL location measurements received at step 16.

NOTE 10: The LMF does not attempt to obtain additional location measurements from the UE or from the NG-RAN.

23. Steps 28-31 in clause 6.3.1 are performed to send the event report to the LCS client or AF.