4.24 Minimization of service interruption

24.5013GPPNon-Access-Stratum (NAS) protocol for 5G System (5GS)Release 17Stage 3TS

The UE and the network may support Minimization of service interruption (MINT). MINT aims to enable a UE to obtain service from a PLMN offering disaster roaming service when a disaster condition applies to the UE’s determined PLMN with disaster condition.

If the UE supports MINT, the indication of whether disaster roaming is enabled in the UE, the one or more "list of PLMN(s) to be used in disaster condition", disaster roaming wait range and disaster return wait range provisioned by the network, if available, are stored in the non-volatile memory in the ME as specified in annex C and are kept when the UE enters 5GMM-DEREGISTERED state. Annex C specifies condition under which the indication of whether disaster roaming is enabled in the UE, the one or more "lists of PLMN(s) to be used in disaster condition", disaster roaming wait range and disaster return wait range stored in the ME are deleted.

Upon selecting a PLMN for disaster roaming as specified in 3GPP TS 23.122 [6]:

a) if the UE does not have a stored disaster roaming wait range, the UE shall perform an initial registration procedure with 5GS registration type value set to "disaster roaming registration" on the selected PLMN; and

b) if the UE has a stored disaster roaming wait range, the UE shall generate a random number within the disaster roaming wait range and start a timer with the generated random number. While the timer is running, the UE shall not initiate registration on the selected PLMN. Upon expiration of the timer, the UE shall perform an initial registration procedure with 5GS registration type value set to "disaster roaming registration" if still camped on the selected PLMN.

Upon determining that a disaster condition has ended and that the UE shall perform PLMN selection as specified in 3GPP TS 23.122 [6]:

a) if the UE does not have a stored disaster roaming wait range, the UE shall perform a registration procedure on the selected PLMN; and

b) if the UE has a stored disaster return wait range, the UE shall generate a random number within the disaster return wait range and start a timer with the generated random number value. While the timer is running, the UE shall not initiate registration on the selected PLMN. Upon expiration of the timer, the UE shall perform a registration procedure if still camped on the selected PLMN.

When the AMF assigns a registration area to the UE registered for disaster roaming services, the AMF shall only include TAIs covering the area with the disaster condition.