cies. IAB supports multi-hop backhauling to provide sufficient range extension in urban infrastructure with pronounced shadowing. It further supports topologically redundant backhauling for robustness and enables load balancing. Relaying is conducted on the radio link layer, which enables efficient processing and con- fines signaling to the RAN with minimum impact on the core network. IAB is compliant with all the relevant 5G deployment options. It leverages the existing NR air interface procedures (with appropriate extensions) to connect to 5GC in standalone mode and to connect to the Evolved Packet Core (EPC) via E-UTRA-NR dual connectivity (EN-DC). Release-15 user equipment (UE) can connect to the 3GPP network via IAB. Access and backhaul interfaces are synchronized at frame level to enable efficient time division multiplexed (TDM) resource sharing while minimizing the latency of multi-hop backhauling. IAB supports inter-node time synchronization via Global Navigation Satel- lite System (GNSS) and cellular over-the-air signaling. IAB support plug-and-play integration of network nodes (assuming sufficient interop- erability testing has been performed), dynamic topology changes during operation, and autonomous recovery in response to link obstruction or node failure. 5.2 Wireless Relaying in 5G IAB builds on the gNB central unit/distributed unit (CU/DU) split architecture (described in Section 4.2) with centralized topology, route, and resource management following software-defined networking (SDN) principles. IAB has been standardized by 3GPP in Release-16 and is being enhanced in Release-17. 5.2.2 Market Drivers The mmWave bands provide abundant capacity, but the high propagation loss in this fre- quency range confines cells to small size SO that densified deployments are necessary to achieve market-wide coverage. While small cells have been available for 3G and 4G radio access technologies, the densified small-cell network has only seen limited commercial suc- cess, in part due to the high backhauling cost. M