5G new radio (NR) requires a very dense deployment of cellular infrastructure, which poses a great economical challenge if traditional fiber backhaul links are used. To cope with this problem, 3GPP introduced integrated access and backhaul (IAB), aiming to use wireless backhaul to provide high capacity and great deployment flexibility. The multi-hop and multi-route topology for this new type of access networks challenges the existing retransmission-/repetition-based reliability-enhancing technique, such as ARQ/HARQ and packet duplication. However, it also opens up new opportunities for novel reliability enhancement techniques. In this paper, taking advantage of the more complex network topology of IAB, we propose to use linear network coding as a potentially better solution to improve end-to-end latency and reliability. We discuss its placement in the IAB protocol stack, and propose two novel schemes to improve the performance of network coding in the IAB network: the rate-proportional traffic splitting scheme in the multi-route scenario, and the adaptive coded-forwarding scheme in the multi-hop scenario. Simulation results show that in some typical IAB scenarios our network coding solution has considerable performance gains over the existing repetition-based technology.
