ted, it conducts RLF recovery using the RRC Connection Reestablishment procedure (3GPP TS 38.300, clause 9.2.3). In this procedure, the IAB node MT selects a new parent node cell, where it reestablishes RRC connectivity to this or another IAB donor CU. The detailed recovery after reestablishment of RRC connec- tivity essentially follows steps 2 and 3 in the parent change procedures described above. If the backhaul RLF recovery procedure fails, the IAB node MT enters RRC IDLE state. At this point, it may reestablish network connectivity through the network integration pro- cedure. When backhaul RLF recovery fails and the IAB node has descendant nodes, it can inform the child nodes about backhaul RLF via a notification message (Figure 5.2.14). The child nodes may pass this notification on its downstream direction. This procedure permits the descendant nodes to proactively engage in RLF recovery and reestablish their own back- haul connectivity. In this process, topology flips may occur, where an IAB node recovers backhaul connectivity via a former child or descendant node. Backhaul RLF recovery may introduce service interruption and packet loss. However, it allows the IAB network to autonomously retain connectivity. After backhaul RLF recovery, the parent change and topological redundancy procedures can be invoked by the IAB donor to reoptimize the network. Figure 5.2.14 Notification of RLF to downstream IAB nodes. IAB-node IAB-node RLF notification IAB-node References 5.2.4 Outlook IAB has been designed for the support of highly densified 5G deployments. By leveraging the benefits of mm Waves for backhauling, IAB can significantly reduce deployment costs for the rollout of mmWave access over an extended area. Integration of access and backhaul is crucial to achieve spectral efficiency. IAB supports a variety of features that are novel for cellular networks such as multi-hop backhauling, dynamic topology changes and support, topological redundancy, and autonomous failure recovery procedures. The initial IAB specifi