ies to backhaul links where both link endpoints can support narrow beams via extended antenna arrays. On the access link, the UE usually has limited beamforming capabilities due to its small size, and its beams are therefore rather broad. For IAB deployments using sub-6 GHz, cross-link interference (CLI) becomes a more significant factor that needs to be considered during operation. Since the problem of CLI also applies to access links, 3GPP has developed a CLI mea- surement framework in Release-16. While this framework aims to enable dynamic Time Division Duplexing (TDD) on access links, it can also be applied to CLI issues in IAB. Resource coordination relies on time synchronization among IAB nodes and IAB donor. For this reason, IAB supports time synchronization via GNSS and via hop-by-hop over-the-air (OTA) signaling across the IAB topology. The OTA solution is beneficial if GNSS is not available such as for indoor deployments. It leverages existing access link 5.2 Wireless Relaying in 5G Time slot Backhaul DL TX Parent node DU Backhaul UL RX Backhaul DL RX IAB-node MT Backhaul UL TX Backhaul DL TX IAB-node DU Backhaul UL RX Backhaul DL RX Child node MT Backhaul UL TX Figure 5.2.11 Time alignment of IAB node transmission and reception. synchronization methods between a gNB-DU and a UE (and therefore also MT), which achieves sufficient accuracy within the cyclic prefix defined by the orthogonal frequency division multiplexing (OFDM) numerology. While time synchronization achieves clock alignment among IAB nodes, it is still neces- sary to determine the relative offset of the system frame boundaries within the topology. Due to the finite propagation delay of the air interface, data transmission and reception cannot be time-aligned. NR compensates for this delay by moving the UE's uplink transmissions up in time SO that the DU's uplink reception and downlink transmission are sufficiently time-aligned. In a multi-hop topology, there are various options for relative time alignment of adjacent IAB nodes with differ