Content for  TS 23.273  Word version:  18.5.0

If the UE is in CM-IDLE state, UE instigates the UE triggered Service Request as defined in clause 4.2.3.2 of TS 23.502 in order to establish a signalling connection with the AMF.

The UE sends an MO-LR Request message included in a UL NAS TRANSPORT message. The MO-LR Request may optionally include up to three LPP positioning message(s). Different types of location services can be requested: location estimate of the UE, location estimate of the UE to be sent to an LCS client or AF, or location assistance data. If the UE is requesting its own location or that its own location be sent to an LCS client or AF, this message carries LCS requested QoS information (e.g. accuracy, response time, LCS QoS Class), the requested maximum age of location, the requested type of location (e.g. "current location", "current or last known location") and, optionally for a current location, a scheduled location time. If the UE is requesting that its location be sent to an LCS client, the message shall include the identity of the LCS client or the AF, and may include the address of the GMLC through which the LCS client or AF (via NEF) should be accessed. In addition, a Service Type indicates which MO-LR service of the LCS Client is requested by the UE may be included. The message also may include a pseudonym indicator to indicate a pseudonym should be assigned by the network and transferred to the LCS Client as the UE's identity. The message may also include integrity requirements including Time-to-Alert (TTA), Target Integrity Risk (TIR) and Alert Limit(AL). Definitions of these parameters are specified in TS 38.305. If the UE is instead requesting location assistance data, the embedded LPP message specifies the type of assistance data and the positioning method for which the assistance data applies. For an LCS 5GC-MO-LR requesting location transfer to an LCS Client or AF, the AMF shall assign a GMLC address, i.e. VGMLC address, which is stored in the AMF. If a VGMLC address is not available, the AMF may reject the location request. The AMF verifies the subscription profile of the UE and decides if the requested service is allowed or not by checking the Mobile Originated data retrieved from UDM during the UE Registration Procedure, as defined in clause 4.2.2.2.2 of TS 23.502. If the requested type of location is "current or last known location" and the requested maximum age of location information is available, the AMF verifies whether it stores the previously obtained location estimate and related timestamp (if available) of the target UE. If the AMF stores the location estimate and the related timestamp (if available) and the location estimate satisfies the requested accuracy and the requested maximum age of the location, the AMF skips steps 3 - 6.

The AMF selects an LMF as described in clause 5.1. AMF may be configured locally a mapping table of UE identity e.g. MSISDN and LMF address. When receiving a MO-LR, AMF determines LMF based on local configuration or by retrieving from UDM in the UE LCS subscriber data. If the AMF is aware that the UE is served by a MBSR, it would select the LMF that can support the MBSR handling.

The AMF invokes the Nlmf_Location_DetermineLocation service operation towards the LMF. The service operation includes an LCS Correlation identifier, the serving cell identity, the client type, an indication whether a location estimate, or location assistance data is requested, UE Positioning Capability if available, a list of MO-LR subscribed assistance data and any embedded LPP message(s) in the MO-LR Request. If the UE's location is requested, the service request may include an indication if UE supports LPP, the requested QoS, Supported GAD shapes and any scheduled location time. If location assistance data is requested, the embedded LPP message(s) will convey the requested types of location assistance data. If any of the procedures in clause 6.11.1 or 6.11.2 are used the service operation includes the AMF identity. Once an AMF has selected an LMF it must continue to use that LMF for the duration of the session. To support location service in PNI-NPN with signalling optimisation, the AMF also includes a contact address (Notification Target Address, e.g. a URI) and a Notification Correlation ID, which is used by LMF to provide location determination to H-GMLC directly. If the AMF is aware that the UE is served by a MBSR, it provides the indication to the LMF.

If the UE is requesting its own location, the actions described in clause 6.11 are performed together with the actions described for step 12 in clause 6.1.2 if a scheduled location time is present. If the UE is instead requesting location assistance data, the LMF transfers this data to the UE as described in clause 6.11.1. The LMF determines the exact location assistance data to transfer according to the type of data specified by the UE, the UE location capabilities, the MO-LR subscribed assistance data and the current cell. If the LMF is informed that the UE is served by a MBSR, the LMF may perform the operation of clause 6.1.4 step 5 to step 7, or step 8 to step 10, to obtain the MBSR location information. The LMF will take the MBSR location into account when determining the UE's location. If H-GMLC contact address and the Notification Correlation ID is received in step 11, and the LMF determines to use local AMF for obtaining Non-UE Associated Network Assistance Data, as described in clause 6.11.3, the LMF responds to AMF in the Nlmf_location_determineLocation Response to indicate that the location determination will be sent directly to GMLC. When LMF determines the UE location, it executes the step 28 as described in clause 6.3.1.

When a location estimate best satisfying the requested QoS has been obtained or when the requested location assistance data has been transferred to the UE, the LMF returns the Nlmf_Location_DetermineLocation Response towards the AMF. The service operation includes the LCS Correlation identifier, the location estimate, if this was obtained, its age and accuracy and may include information about the positioning method. If a location estimate was not successfully obtained, or if the requested location assistance data could not be transferred successfully to the UE, a failure cause is included in the service operation. The service operation may also include the UE Positioning Capability if the UE Positioning Capability is received in step 5 including an indication that the capabilities are non-variable and not received from AMF in step 4. If the UE is requesting location assistance data, steps 7 to 12 are skipped.

If the location estimate was successfully obtained, the AMF invokes the Ngmlc_Location_LocationUpdate service operation towards to the VGMLC assigned in the step 2. The service operation carries the identity of the UE, the event causing the location estimate (5GC-MO-LR) and the location estimate, its age, obtained accuracy indication and the LCS QoS Class requested by the target UE. In addition, the service operation may include the pseudonym indicator, the identity of the LCS Client, AF ID, the GMLC address, the timestamp of the location estimate and the Service Type specified by the UE, if available.

If the UE did not request transfer of its location to an LCS Client or AF in step 2, steps 8 to 11 are skipped. If the VGMLC is same NF instance as HGMLC this step is skipped. Otherwise VGMLC invokes the Ngmlc_Location_LocationUpdate service operation towards to the HGMLC (the VGMLC may query the NRF to obtain the address of the HGMLC) including the information received from the AMF.

If the pseudonym indicator is included in the MO-LR Location Information, the HGMLC assigns a pseudonym to the UE. If the identified LCS Client is not accessible by the HGMLC, step 9a and step 10a are skipped. Otherwise the GMLC transfers the location information to the LCS client, carrying the identity or the pseudonym of the UE, the event causing the location estimate (5GC-MO-LR), the Service Identity, if available, and the location estimate, the timestamp of the location estimate (if available) and its age, in accordance with the LCS QoS Class requested by the target UE. If the UE requested LCS QoS class was Assured, GMLC sends the result to the LCS client only if the result has been indicated to fulfil the requested accuracy. If the UE requested LCS QoS class was Best Effort, GMLC sends whatever result it received to the LCS client with an appropriate indication if the requested accuracy was not met.

If the AF ID is included in step 1, the HGMLC assigns the NEF address based on local configuration or via NRF and invokes Ngmlc_Location_LocationUpdateNotify service request towards the NEF, carrying the AF ID. The location information parameters sent within this service operation are same as the step 9a except that no pseudonym is included.

If the identified AF is not accessible by the NEF, step 9b-2 and step 10b-1 are skipped. Otherwise, the NEF transfer the location information to the identified AF by invoking the Nnef_Location_LocationUpdateNotify service.

If the LCS Client does not support MO-LR (for temporary or permanent reasons) or cannot handle the location estimate of the UE, e.g. the LCS Client does not know the Service Identity, or the UE does not register to the LCS Client, the LCS Client has no corresponding data of the UE, the LCS Client shall return the Location Information ack message to the HGMLC with a suitable error cause. Otherwise, the LCS Client handles the location estimate according to the Service Identity, sends the GMLC or the HGMLC the Location Information ack message signalling that the location estimate of the UE has been handled successfully.

If the AF cannot handle the location estimate of the UE, e.g. the UE does not register to the AF, the AF has no corresponding data of the UE, the AF shall respond to the Nnef_Location_LocationUpdateNotify service request with a suitable error cause. Otherwise, the AF handles the location estimate according to the Service Identity and respond to the Nnef_Location_LocationUpdateNotify service request indicating that the location estimate of the UE has been handled successfully.

The NEF sends a Ngmlc_Location_LocationUpdateNotify service response towards the HGMLC with the outcome of the operation.

If the VGMLC is same NF instance as HGMLC this step is skipped. If the identified LCS Client or AF is not accessible, the HGMLC sends a Ngmlc_Location_LocationUpdate service response to VGMLC with an appropriate error cause. Otherwise, the response shall include an acknowledgement. The message shall specify whether the location estimate of the UE has been handled successfully by the identified LCS Client or AF, and if not, the corresponding error cause obtained in step 10. In addition, the HGMLC may record charging information both for the UE and inter-working revenues charges.

If the VGMLC receives the MO-LR Location Information Acknowledgement from the HGMLC, if the identified LCS Client or AF is not accessible, the VGMLC sends a Ngmlc_Location_LocationUpdate service response to AMF with an appropriate error cause. Otherwise, the response shall include an acknowledgement. The message shall specify whether the location estimate of the UE has been handled successfully by the identified LCS Client or AF, and if not, the corresponding error cause obtained in step 9 or 10. In addition, the VGMLC may record charging information both for the UE and inter-working revenue charges. If the VGMLC receives Ngmlc_Location_LocationUpdate Request from the AMF and it is not required to send to any LCS Client or AF, the VGMLC may record charging information for the UE and response the Ngmlc_Location_LocationUpdate Request to the AMF.

The AMF sends an MO-LR Response message included in a DL NAS TRANSPORT message. If the UE is requesting its own location, the response carries any location estimate requested by the UE and the timestamp of the location estimate (if available) including the indication received from LMF whether the obtained location estimate satisfies the requested accuracy or not, or an indicator whether a location estimate was successfully transferred to the identified LCS client or AF. If the location estimate was successfully transferred to the identified LCS Client or AF, the MO-LR Response message shall specify whether the location estimate of the UE has been handled successfully by the identified LCS Client or AF, and if not, the corresponding error cause obtained in step 13. In addition, AMF may record charging information.