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full Contents for  TS 23.273  Word version:   16.3.0

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1…   4…   4.2a…   4.3…   5…   6…   6.1.2   6.2   6.3…   6.3.2…   6.4   6.5…   6.7…   6.8   6.9…   6.10…   6.11…   6.12…   6.13…   6.14…   7…   8…   A…   B…

 

6.1.2  5GC-MT-LR Procedure for the commercial location serviceWord-p. 35
Figure 6.1.2-1 illustrates the general network positioning requested by the LCS clients or the AF external to the PLMN. In this scenario, it is assumed that the target UE may be identified using an SUPI or GPSI. This procedure is applicable to a request from an external LCS client or AF for a current location of the target UE, and it is assumed that
  • Privacy verification may be required for the location service request;
  • The LCS client or the AF needs to be authorised to use the location service.
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Step 1.
The external location services client or the AF (via NEF) sends a request to the (H)GMLC for a location and optionally a velocity for the target UE which may be identified by an GPSI or an SUPI. The request may include the required QoS, supported GAD shapes, LCS client type and other attributes. (H)GMLC (for 1a) or NEF (for 1b) authorizes the External Client or the AF for the usage of the LCS service. If the authorization fails, step 2-23 are skipped and (H)GMLC (for 1a) or NEF (for 1b) responds to the external Client or the AF the failure of the service authorization in step 24. In some cases, the (H)GMLC derives the GPSI or SUPI of the target UE and possibly the QoS from either subscription data or other data supplied by the LCS client or AF.
The LCS request may carry also the Service Identity and the Codeword and the service coverage information. The (H)GMLC may verify that the Service Identity received in the LCS request matches one of the service identities allowed for the LCS client or AF. If the service identity does not match one of the service identities for the LCS client or AF, the (H)GMLC shall reject the LCS request. Otherwise, the (H)GMLC can map the received service identity in a corresponding service type.
If the LCS service request contains the pseudonym of the target UE and the (H)GMLC cannot resolve the PMD address from the pseudonym, the (H)GMLC itself determines the verinym (GPSI or SUPI) of the target UE. If the (H)GMLC can resolve the address of PMD from the pseudonym, the HGMLC requests the verinym from its associated PMD. If (H)GMLC is not able to obtain the verinym of the target UE, the (H)GMLC shall cancel the location request.
If the requested type of location is "current or last known location" and the requested maximum age of location information is available, the (H)GMLC verifies whether it stores the previously obtained location estimate of the target UE. If the HGMLC stores the location estimate and the location estimate satisfies the requested accuracy and the requested maximum age of location, the (H)GMLC checks the result of the privacy check at step 2. If the result of the privacy check for call/session unrelated class is "Location allowed without notification" then steps 3-23 may be skipped.
If location is required for more than one UE, the steps following below may be repeated.
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Step 1b-1.
AF sends the LCS service request to the NEF.
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Step 1b-2.
The NEF identifies based on the QoS attribute received from the location request that higher than cell-ID level location accuracy is required and invokes the Ngmlc_Location_ProvideLocation_Request service operation to the (H)GMLC, which contains the attributes received from the AF request. The NEF may also invoke the Ngmlc_Location_ProvideLocation_Request service operation to the (H)GMLC for lower than cell-ID location accuracy as an implementation option.
If location is required for more than one UE, the steps following below may be repeated and in that case the NEF or HGMLC receiving location request, shall verify whether the number of Target UEs in the LCS request is equal to or less than the Maximum Target UE Number of the LCS client. If Maximum Target UE Number is exceeded, the NEF or HGMLC shall reject the LCS request, the steps 2-23 are skipped, and then GMLC respond to the client with proper error cause in the step 24.
NOTE 1:
If cell-ID level or lower than cell-ID level location accuracy is required in the location request, the NEF may invoke an Namf_EventExposure_Subscribe service operation to subscribe location event reporting from the AMF for the target UE as further described in clause 6.5.
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Step 2.
The (H)GMLC invokes a Nudm_SDM_Get service operation towards the UDM of the target UE to get the privacy settings of the UE identified by its GPSI or SUPI. The UDM returns the target UE Privacy setting and the SUPI of the UE. The (H)GMLC checks the privacy settings. If the target UE is not allowed to be located, steps 3-23 are skipped.
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Step 3.
The (H)GMLC invokes a Nudm_UECM_Get service operation towards the UDM of the target UE with SUPI of this UE. The UDM returns the network addresses of the current serving AMF and additionally the address of a VGMLC (for roaming case). If the location request is an immediate location request, the (H)GMLC checks the country codes of the serving node addresses. If the (H)GMLC finds the current AMF is out of the service coverage of the (H)GMLC, the (H)GMLC returns an appropriate error message to the LCS client or AF.
NOTE 2:
The UDM is aware of the serving AMF address at UE registration on an AMF as defined in clause 4.2.2.2.2 of TS 23.502. The UDM is aware of a serving VGMLC address at UE registration on an AMF as defined in clause 4.2.2.2.2 of TS 23.502.
NOTE 3:
The HGMLC can also query the HSS of the target UE for a serving MME address as described in clause 9.1.1 of TS 23.271. The EPC-MT-LR procedure described in clause 9.1.15 of TS 23.271, excluding the UE availability event, may then be performed instead of steps 4-23, e.g. if the HSS returns an MME address but the UDM does not return an AMF address.
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Step 4.
For a non-roaming case, this step is skipped. In the case of roaming, the HGMLC may receive an address of a VGMLC (together with the network address of the current serving AMF) from the UDM in step 3, otherwise, the HGMLC may use the NRF service in the HPLMN to select an available VGMLC in the VPLMN, based on the VPLMN identification contained in the AMF address received in step 3. The HGMLC then sends the location request to the VGMLC by invoking the Ngmlc_Location_ProvideLocation service operation towards the VGMLC. In the cases when the HGMLC did not receive the address of the VGMLC, or when the VGMLC address is the same as the HGMLC address, or when both PLMN operators agree, the HGMLC sends the location service request message to the serving AMF. In this case, step 4 is skipped. If the result of privacy check indicates that the notification (and verification) based on current location is needed, the HGMLC shall send a location request to the VGMLC indicating "positioning allowed without notification" and VGMLC shall invoke an Namf_Location_ProvidePositioningInfo Request service operation towards the AMF at step 5.
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Step 5.
In the case of roaming, the VGMLC first authenticates that the location request is allowed from this HGMLC, PLMN or from this country. If not, an error response is returned. The (H)GMLC or VGMLC invokes the Namf_Location_ProvidePositioningInfo service operation towards the AMF to request the current location of the UE. The service operation includes the SUPI, the client type and may include the required LCS QoS, supported GAD shapes and other attributes as received or determined in step 1.
NOTE 4:
The location request forwarded at step 4 and step 5 may also carry the result of the privacy check in step 2 which may include a codeword provided by the LCS Client or AF and an indication of a privacy related action as described in clause 5.4.
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Step 6.
If the UE is in CM IDLE state, the AMF initiates a network triggered Service Request procedure as defined in clause 4.2.3.3 of TS 23.502 to establish a signalling connection with the UE.
If signalling connection establishment fails, step 7-13 are skipped and the AMF answers to the GMLC in step 14 with the last known location of the UE (i.e. Cell ID) together with the age of this location.
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Step 7.
If the indicator of privacy check related action indicates that the UE must either be notified or notified with privacy verification and if the UE supports LCS notification (according to the UE capability information), a notification invoke message is sent to the target UE, indicating the identity of the LCS client the Requestor Identity (if that is both supported and available) and whether privacy verification is required.
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Step 8.
The target UE notifies the UE user of the location request and, if privacy verification was requested, waits for the user to grant or withhold permission. The UE then returns a notification result to the AMF indicating, if privacy verification was requested, whether permission is granted or denied for the current LCS request. If the UE user does not respond after a predetermined time period, the AMF shall infer a "no response" condition. The AMF shall return an error response to the (H)GMLC if privacy verification was requested and either the UE user denies permission or there is no response with the UE privacy profile received from the (H)GMLC indicating barring of the location request.
The notification result also indicates the Location Privacy Indication setting for subsequent LCS requests; i.e whether subsequent LCS requests, if generated, will be allowed or disallowed by the UE. The Location Privacy Indication may also indicate a time for disallowing the subsequent LCS requests.
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Step 9.
The AMF invokes the Nudm_ParameterProvision_Update (LCS privacy) service operation to store in the UDM the Location Privacy Indication information received from the UE. The UDM may then store the UE privacy setting information into the UDR as the "LCS privacy" Data Subset of the Subscription Data.
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Step 10-13.
Step 10-13 are the same as steps 6-9 defined in clause 6.1.1.
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Step 14.
The AMF returns the Namf_Location_ProvidePositioningInfo Response towards the (V)GMLC (or HGMLC for roaming when the NL3 reference point is not supported) to return the current location of the UE. The service operation includes the location estimate, its age and accuracy and may include information about the positioning method.
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Step 15.
In the case of roaming, the VGMLC forwards the location estimation of the target UE, its age, its accuracy and optionally the information about the positioning method received at step 14 to the HGMLC. For non-roaming scenario, this step is skipped.
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Step 16.
If the privacy check in step 2 indicates that further privacy checks are needed, the (H)GMLC shall perform an additional privacy check in order to decide whether the (H)GMLC can forward the location information to the LCS client or AF or send a notification if the result of the privacy check requires the notification and verification based on current location. One example when this additional privacy check is needed is when the target UE user has defined different privacy settings for different geographical locations. When an additional privacy check is not needed, the (H)GMLC skips steps 17-23.
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Step 17.
If the result of privacy checks in step 16 indicates that the notification (and verification) based on current location is needed, and in the case of roaming, the (H)GMLC shall send a location request to the VGMLC indicating "notification only",
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Step 18.
The (H)GMLC or VGMLC invokes the Namf_Location_ProvidePositioningInfo service operation towards the AMF to request notification (and verification) based on current location.
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Step 19.
If the UE is in CM IDLE state, the AMF initiates a network triggered Service Request procedure as defined in clause 4.2.3.3 of TS 23.502 to establish a signalling connection with the UE.
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Step 20.
If the UE supports LCS notification, the AMF sends a notification invoke message to the target UE, indicating the identity of the LCS client the Requestor Identity (if that is both supported and available) and whether privacy verification is required.
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Step 21.
Step 21 is the same as step 8.
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Step 22.
The AMF returns the Namf_Location_ProvidePositioningInfo Response towards the (V)GMLC (or HGMLC for roaming when the NL3 reference point is not supported) with an indication of the result of notification and verification procedure performed in steps 20-21.
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Step 23.
In the case of roaming, the VGMLC forwards an indication of the result of notification and verification procedure to the HGMLC. For non-roaming scenario, this step is skipped.
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Step 24.
The (H)GMLC sends the location service response to the external location services client or AF (via the NEF). If the location request from the LCS client contained the pseudonym and the (H)GMLC resolved the verinym from the pseudonym in step 1, the (H)GMLC shall use the pseudonym of the target UE in the location response to the LCS client. If the LCS client or AF requires it, the (H)GMLC may first transform the universal location co-ordinates provided by the AMF into some local geographic system. The (H)GMLC may record charging information both for the external LCS client or AF and inter-network revenue charges from the AMF's network. The location service response from the (H)GMLC to the external LCS client or AF may contain the information about the positioning method used and the indication whether the obtained location estimate satisfies the requested accuracy or not. If in step 2, step 16 or step 23 the (H)GMLC identifies that the target UE is not allowed to be located by the external LCS client or AF, it rejects the LCS service request, and optionally indicate in the response the reason of the rejection, i.e. the target UE is not allowed to be located.
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