for IAB-operation 1c. Optional: IAB-node MT establishes PDU session, e.g., for OAM support 1d. gNB hands over IAB-node MT to suitable IAB-donor 2. IAB-donor configures backhaul connectivity: - Backhaul RLC channels for F1-C - BAP route and for F1-C - IP address allocation 3. IAB-node DU establishes F1-C to IAB-donor gNB-CU Establishment of security layer - Establishment of SCTP - Establishment of F1-AP a: IAB-node MT in standalone mode Integrating Parent IAB-donor IAB-donor IAB-node IAB-node 1a. IAB-node establishes RRC connection with eNB 1b. IAB-node MT registers with EPC via eNB and obtains authorization for IAB-operation 1c. Optional: IAB-node MT establishes PDN connection, e.g., for OAM support 1d. eNB adds IAB-donor as SgNB 2. IAB-donor configures backhaul connectivity: - Backhaul RLC channels for F1-C - BAP route and for F1-C - IP address allocation 3. IAB-node DU establishes F1-C to IAB-donor gNB-CU - Establishment of security layer - Establishment of SCTP - Establishment of F1-AP b: IAB-node MT in EN-DC mode Figure 5.2.12 IAB node integration into network (a) IAB node MT operating in SA mode with 5GC, (b) IAB node MT operating in EN-DC with EPC. 5 NG-RAN Evolution In the topology change scenario, the IAB node MT leverages inter-gNB handover to migrate from the source to the target IAB donor CU (3GPP TS 38.300, clause 9.2.3). The configuration of new RLC channels, BAP route, and IP addresses is the same as in step 2 for intra-IAB donor parent node change described in Figure 5.2.13. The IAB node DU needs to establish a new F1-C association with the target IAB donor CU, where it adopts the target IAB donor CU's cell identifier (5CGI) and potentially also different Physical Cell IDs (PCIs). The UEs served by the migrating IAB node will experience this reconfiguration as a radio link failure and attempt the RRC Configuration Reestablishment procedure to the reconfigured cell. This procedure is certainly more disruptive than the parent node change underneath the same IAB donor CU. Enhancements to mitigate this