IAB Integrated Access and Backhaul
IAB is a 3GPP feature, introduced in Release 16, that lets a gNB (Next Generation Node B) use the same NR (New Radio) spectrum for both the access link serving UEs (User Equipment) and the backhaul link connecting back to the core network, relieving dependency on costly fibre or microwave backhaul, particularly at mmWave (millimetre wave) where dense small cells are wanted but wiring each one is impractical. The architecture splits into an IAB-donor, a full gNB with a wired core connection that terminates the wireline backhaul and hosts the CU (Centralised Unit) functions, and one or more IAB-nodes acting as relays, each with an MT (Mobile Termination) function that behaves like a UE towards its parent node and a DU (Distributed Unit) function serving child UEs or further downstream IAB-nodes; this MT/DU split enables multi-hop chaining, where one IAB-node backhauls through another before reaching the donor.
