5.15.18.2 S-NSSAI location availability information

S-NSSAI location availability information defines additional restrictions to the usage of an S-NSSAI in TAs where the Network Slice availability does not match the TA boundaries. The AMF is configured per S-NSSAI whether to send the S-NSSAI location availability information to supporting UEs.

The S-NSSAI location availability information sent to the UE includes, for each applicable S-NSSAI of the Configured NSSAI, Location information indicating the cells of TAs in the RA where the related S-NSSAI is available if the S-NSSAI is not available in all the cells of the TA.

If the UE has indicated that the UE supports S-NSSAI location availability information in the 5GMM Core Network Capability (see clause 5.4.4a), the AMF may, based on OAM configuration, configure the UE with S-NSSAI location availability information for one or more S-NSSAIs when the AMF allocates an RA where the Network Slice availability does not match whole TAs, by including the S-NSSAI location availability information in the Registration Accept message or the UE Configuration Command message. A UE that receives S-NSSAI location availability information applies the information as follows.

1. If the S-NSSAI is rejected in the RA or rejected partially in the RA or rejected with a cause code that allows attempting to register the S-NSSAI again, the UE can request the S-NSSAI only if the S-NSSAI location availability information indicates that the S-NSSAI is available at the cell where the UE is camping.

2. If the S-NSSAI is in the Partially Allowed NSSAI or in the Allowed NSSAI and the UE is in a cell within the RA but outside the NS-AoS of the S-NSSAI, the following applies:

a. The UE shall not activate User Plane resources for any already established PDU Session with that S-NSSAI including the case of always-on PDU Session.

b. The UE shall not send user data as payload of a NAS message (see clause 5.31.4.1) in uplink direction.

c. For an already established PDU Session, the supporting UE may initiate signalling for PDU Session release procedure or PDU Session modification procedure (i.e. for PS data off status change reporting).

3 If the UE has overlapping areas between non-allowed area, a cell inside the NS-AoS, then the non-allowed area restriction applies.

4. If the S-NSSAI is in the Partially Allowed NSSAI or in the Allowed NSSAI and the UE in CM-CONNECTED state moves from a cell inside the NS-AoS to a cell outside the NS-AoS and the User Plane resources are active for a PDU Session on that S-NSSAI, the NG-RAN releases the User Plane resources as described in step 1d of the AN initiated Release of a PDU Session in clause 4.3.4.2 of TS 23.502 [3]. The SMF also deactivates the PDU Session as described in step 3a in clause 4.3.4.2 of TS 23.502 [3].

NOTE 1: By Radio Resource Management and existing mechanisms in NG-RAN, handover can be used to keep the UE in the NS-AoS or steer the UE to enter the NS-AoS as long as radio conditions allow it.

NOTE 2: Since the S-NSSAI location availability information is not a used as a trigger for the UE to perform MRU due to mobility, i.e. the UE performs MRU due to mobility upon changing to a new TA outside the UE's Registration Area, the S-NSSAI remains registered and is included in the Allowed NSSAI when the UE exits the NS-AoS. If the S-NSSAI is subject for NSAC, the S-NSSAI is counted towards NSAC as described in clause 5.15.11 also when the UE is outside the NS-AoS.