5.49.1.4 Support of network slicing for UEs served by a MWAB

A MWAB-gNB can be configured to associate S-NSSAI(s) in the MWAB Broadcasted PLMN/SNPN to the traffic descriptor for selection of the BH PDU Sessions parameters e.g. use dedicated S-NSSAI in BH PLMN/SNPN. If no such association exists for a specific S-NSSAIs of the MWAB Broadcasted PLMN/SNPN, the MWAB-gNB associates this S-NSSAI to default traffic descriptors for the selection of BH PDU Session(s) for the related N2 and/or N3 backhauling. The MWAB-gNB requests the BH PDU sessions as specified in clause 5.49.1.2.

When the MWAB-gNB obtains, for a UE it serves, the S-NSSAI of a PDU Session from the UE's PDU session context during PDU session establishment, it checks whether a configured association exists for the S-NSSAI of the PDU session of the UE and, if so, it uses the related BH PDU session for the UE's PDU Session.

If a new BH PDU Session needs to be established for supporting a UE's traffic for a S-NSSAI in the MWAB-Broadcasted PLMN/SNPN, after the completion of the PDU session establishment procedure for the UE served by the MWAB-gNB, the MWAB-UE establishes the new BH PDU Session and, upon it being established, the MWAB gNB triggers a PDU Session Resource Modify Indication procedure (see clause 8.2.5 of TS 38.413 [34]) to shift the N3 traffic for the UE to the new BH PDU sessions.

NOTE 1: Due to the limitation of the maximum number of PDU sessions supported by a UE, it is expected that there can only be a small number of dedicated BH PDU sessions for specific S-NSSAI(s) in the MWAB-broadcasted PLMN.

NOTE 2: If the dedicated BH PDU Session the MWAB-gNB needed for traffic associated with an S-NSSAI is not available (e.g. because S-NSSAI of the BH PDU Session is not allowed or other reasons), the MWAB-gNB can deliver the traffic associated with the S-NSSAI via another BH PDU Session based on implementation.