5.35.6 IAB operation involving EPC

When the IAB-donor gNB has connection to both EPC and 5GC, based on PLMN configuration, there are two possible operation modes:

• the IAB-node connects to a 5GC via the IAB-donor gNB, while the UEs served by the IAB-node connect to EPC with Dual Connectivity as defined in TS 37.340 [31]. In this operation mode, the IAB-donor gNB has connection to an eNB and the 5GC is restricted for IAB-node access only; and
• the IAB-node connects to an EPC via the IAB-donor gNB with Dual Connectivity as defined in TS 37.340 [31], while the UEs served by the IAB-node connect to the 5GC. In this operation mode, the EPC is restricted for IAB-node access only.

To support the above operation modes, the IAB-UE shall be configured to select only a specific PLMN (as defined in TS 23.122 [17]) and whether it needs to connect to 5GC or EPC.

NOTE: For a particular PLMN, it is expected that only one of the modes would be deployed in a known region.