ction that wirelessly "self-backhaul" via neighbor nodes to the next fiber point. While wireless backhauling uses part of the mmWave capacity, the integration with access enables flexible and spectrally efficient resource utilization. IAB can also be applied for or in combination with sub-6 GHz frequencies. It is possible, for instance, to support sub-6 GHz access net- works with mmWave-based backhauling. The standardization of IAB provides interoperability and therefore allows integration of relays from different vendors into the same network. This lowers cost through com- moditization, which is an important factor for a technology that relies on rollout in large quantities. Standardization further establishes test scenarios to ensure that performance guarantees can be met. However, one must remember that, even though IAB network inter- faces are fully defined in 3GPP, it is unlikely that it would be possible to deploy IAB network nodes in a "plug-and-play," manner and a certain amount of integration and interoperabil- ity testing will still need to be performed by operators deploying an IAB network. In this chapter, we describe the IAB architecture and elaborate on the design decisions made to accommodate multi-hop transport, Quality of Service (QoS), and spectrally effi- cient resource sharing between backhauling and access. We further highlight critical factors to be considered such as flow and congestion control, duplexing constraints, cross-link interference, and inter-node time synchronization. Finally, autonomous network integra- tion of IAB nodes and dynamic topology changes are discussed. 5.2.1 Key Ideas IAB enables economic rollout of 5G mm Wave access network. Due to flexible and spec- trally efficient resource sharing between access and backhaul, it can substantially reduce the number of fiber connections without need for additional spectrum. Access and back- haul can also be operated in different bands. IAB is not limited to mmWave and can also be applied for or in combination with sub-6 GHz frequen