5.40.4 Registration for Disaster Roaming service

For a UE to receive Disaster Roaming service from a PLMN providing Disaster Roaming service, the UE sends a NAS Registration Request message with Registration Type value "Disaster Roaming Initial Registration" or "Disaster Roaming Mobility Registration Update":

• When the AMF in the PLMN providing Disaster Roaming service receives a NAS Registration Request with Registration Type set to "Disaster Roaming Initial Registration" or "Disaster Roaming Mobility Registration Update";
• the AMF controls if the UE is allowed to access Disaster Roaming service in the area with Disaster Condition as specified in clause 4.2.2.2.2 of TS 23.502 [3];
• the AMF may provide the Disaster Roaming service indication to AUSF and UDM as specified in clause 4.2.2.2.2 of TS 23.502 [3] and TS 33.501 [29]. The AMF may provide the Disaster Roaming service indication to SMF as specified in clause 4.3.2 of TS 23.502 [3].

NOTE 1: The AUSF and the UDM are configured with Disaster Condition via OAM based on operator policy and the request by the government agencies. Based on this local configuration and/or the Disaster Roaming service indication, the AUSF can execute authentication of the UE and the UDM can provides the subscription data for a Disaster Roaming service to the AMF and/or the SMF.

To support the Disaster Roaming service, the PLMN providing Disaster Roaming service is configured to support communication with the network entities in the HPLMN of the UE, i.e. configurations related to roaming interfaces for communication between serving PLMN and HPLMN shall be deployed in the affected entities. This communication between the PLMNs need only be enabled during the Disaster Condition.

The Disaster Roaming service is limited to the impacted geographic area with Disaster Condition. The NG-RAN nodes and AMF in the PLMN providing Disaster Roaming service are configured with the area information, i.e. a list of TAIs which can be formulated by the PLMN providing the Disaster Roaming service based on the geographic area with Disaster Condition in the other PLMN(s).

The AMF in the PLMN providing Disaster Roaming service provides the mobility restriction list to the NG-RAN as specified in clause 5.3.4.1.1 considering the area with Disaster Condition and also indicating that EPC is not an allowed core network.

NOTE 2: From the perspective of emergency services, a UE is following procedures as described in clause 4.24 of TS 24.501 [47] when registered for Disaster Roaming service.

NOTE 3: When the UE is registered for Disaster Roaming service, SMS over NAS can be supported with the procedures as described in clause 4.13.3.1 of TS 23.502 [3] based on subscription data.