Counter Waves Link Activation Policy for Latency Control in In-Band IAB Systems

Abstract

3GPP’s Integrated Access and Backhaul (IAB) architecture is expected to deliver a cost-efficient option for deploying 5G New Radio (NR) systems. However, IAB relies on multi-hop wireless communications, and packet latency therefore becomes a critical metric in such systems. Latency minimization in the in-band backhauling regime involves dynamical scheduling of active transmission links so as to avoid half-duplex conflicts, which brings significant control overheads. In this paper, by using the formalism of Markov decision processes (MDP), we identify a general fixed link activation policy and the associated policy design algorithm for tree-shaped in-band IAB systems with half-duplex constraints. The proposed policy, named “counter waves”, does not require signalling between the IAB donor and nodes and provides stable low latency for low-to-medium traffic conditions spanning up to 60% of the capacity region of the system.