[{"name":"S2-2208121","title":"LS from CT WG1: LS on UE selecting a non-allowed TAI in satellite access broadcasting multiple TACs per cell","source":"CT WG1","contact":"Mikael Wass","contact-id":42217,"tdoctype":"LS in","for":"Action","abstract":"In their work on NR satellite access and the topic of multiple broadcast TAIs, CT WG1 has noted the stage 2 requirements for service area restrictions in TS 23.501, clause 5.4.11.8: The AMF receives the broadcast TAI (if a single TAI is broadcast) or all broadcast TAIs (if multiple TAIs are broadcast) from the NG-RAN as described clause 5.4.11.7. The AMF provides the UE with Service Area Restrictions which consist of either Allowed Areas or Non-Allowed Areas, as described in clause 5.3.4.1.2. The UE and AMF consider the UE to be in a Non-Allowed Area if none of the broadcast TAIs is Allowed. The UE and AMF consider the UE to be in an Allowed Area if at least one broadcast TAI is allowed. The corresponding stage 3 requirements to select a current TAI from multiple broadcast TAIs are specified in TS 24.501, clause 4.23.5, where the UE selects the TAI from the TACs supported by the selected PLMN. Note, however, that for the case when the satellite cell is a shared network cell, then there is an additional requirement on PLMN selection applicable which is specified in TS 23.122, clause 4.4.3: when a selected cell is a suitable cell for multiple PLMN identities, then the UE is mandated to select the registered PLMN if is available among these PLMN identities. Since logically PLMN selection is taking place before determination of the current TAI, the requirement from TS 23.122 takes precedence. As a result, it is possible that when all of the following is fulfilled: - the network is allocating TAI lists including TAIs from different, equivalent PLMNs, - the network is broadcasting multiple TAIs in its satellite NG-RAN cells, o whereby these TAIs belong to different, equivalent PLMNs, and o TAIs of one PLMN belong to the allowed area whereas TAIs of the equivalent PLMN belong to the non-allowed area, then - there can be cases where the UE selects a TAI that is part of the non-allowed area (because it belongs to the registered PLMN) although there would be an allowed TAI of an equivalent PLMN available. Note that this can occur both when the UE is actually located in an allowed TAI and when it is located in a non-allowed TAI. One example for such a case is as follows: The UE is assigned a registration area that contains at least one equivalent PLMN in addition to the registered PLMN; The UE is assigned an allowed area; The TACs of the registered PLMN which are part of the broadcast TAI list are not in the allowed area; The UE receives broadcast information in a satellite cell where at least one TAC of an equivalent PLMN part of the broadcast TAI list is included in the allowed area. CT WG1 has not made a systematic study of possible other corner cases, including the scenario above when the UE could select a TAI that is part of the allowed area, and has decided to not make any changes to specification under CT WG1 remit because of the above-described scenario, but would like to inform SA WG2 of these observations.","secretary_remarks":"Noted","agenda_item_sort_order":54,"ainumber":"8.11","ainame":"Architecture aspects for using satellite access in 5G (5GSAT_ARCH)","tdoc_agenda_sort_order":12430,"status":"noted","reservation_date":"2022-09-21 05:20:40","uploaded":"2022-09-22 05:01:53","revisionof":"","revisedto":"","release":"Rel-17","crspec":"","crspecversion":"","workitem":"","crnumber":"","crrevision":"","crcategory":"","tsg_crp":"","lsreplyto":"","lsto":"SA WG2","Cc":"","lsoriginalls":"C1-225160","lsreply":"","link":"https:\/\/www.3gpp.org\/ftp\/tsg_sa\/WG2_Arch\/TSGS2_153E_Electronic_2022-10\/Docs\/S2-2208121.zip","group":"S2","meeting":"S2-153-e","year":2022,"uicc_affected":"","me_affected":"","ran_affected":"","cn_affected":"","clauses_affected":"","crsinpack":null,"crsinpacknumber":0},
{"name":"S2-2208135","title":"LS from CT WG4: Reply LS on Nudm_UEContextManagement service for satellite NG-RAN","source":"CT WG4","contact":"Ulrich Wiehe","contact-id":73600,"tdoctype":"LS in","for":"Information","abstract":"CT WG4 thanks CT WG1 for their LS on Nudm_UEContextManagement service for satellite NG-RAN, which asks for action: Action: CT WG1 respectfully requests CT WG4 to update Nudm_UEContextManagement service so that the AMF can be made aware of whether each of the TAIs of the current cell should be forbidden or not. Answer: Taking into account the approved CR #4131 to TS 24.501 in CP-220147 (which was attached to CT WG1's LS) and also the approved CR #4305 to TS 24.501 in C1-223556 (which adds additional modifications to clause 5.1.1.4), CT WG4 respectfully ask CT WG1 to note that the AMF is made aware of the complete list of the UE's forbidden TAIs in the Serving PLMN as part of the Nudm_SDM Get service operation. This allows the AMF to determine whether each of the TAIs of the current cell should be forbidden or not. However, the list of forbidden TAIs sent from UDM to AMF as part of the UE's subscription information does not indicate which TAIs are forbidden for roaming and which TAIs are forbidden for regional provision of service. Consequently the AMF cannot determine based on the UE's subscription information received from the UDM whether a given TAI of the current cell should be included in a) the Forbidden TAI(s) for the list of '5GS forbidden tracking areas for roaming' IE; or b) the Forbidden TAI(s) for the list of '5GS forbidden tracking areas for regional provision of service' IE; or c) both; in the REGISTRATION ACCEPT message. CT WG4 could not reach consensus whether the changes in C1-223556 actually require updates to the Nudm_SDM Get service operation, allowing to indicate per forbidden TAI whether the TAI is forbidden for roaming or forbidden for regional provision of services, based on UE subscription information.","secretary_remarks":"Noted","agenda_item_sort_order":54,"ainumber":"8.11","ainame":"Architecture aspects for using satellite access in 5G (5GSAT_ARCH)","tdoc_agenda_sort_order":12440,"status":"noted","reservation_date":"2022-09-21 05:20:41","uploaded":"2022-09-22 05:01:53","revisionof":"","revisedto":"","release":"Rel-17","crspec":"","crspecversion":"","workitem":"","crnumber":"","crrevision":"","crcategory":"","tsg_crp":"","lsreplyto":"","lsto":"CT WG1","Cc":"SA WG2","lsoriginalls":"C4-224409","lsreply":"","link":"https:\/\/www.3gpp.org\/ftp\/tsg_sa\/WG2_Arch\/TSGS2_153E_Electronic_2022-10\/Docs\/S2-2208135.zip","group":"S2","meeting":"S2-153-e","year":2022,"uicc_affected":"","me_affected":"","ran_affected":"","cn_affected":"","clauses_affected":"","crsinpack":null,"crsinpacknumber":0}]