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A Survey of Delay-Oriented Dynamic Link Scheduling Policies for 5G/6G Integrated Access and Backhaul Systems
Integrated Access and Backhaul (IAB) is expected to become a key part of the 5G and future cellular systems enabling cost-controlled network densification. IAB relies upon multi-hop relaying, which makes delay a critical factor, especially for the half-duplex operational regime where only a subset of access and backhaul links can be scheduled simultaneously. Numerous dynamic link scheduling policies were developed in the past for different applications, backpressure being the best known example. Each such policy offers its own balance of supported network throughput, computational complexity and end-to-end delay performance. The latter metric is the least investigated in the literature and is the most important for multi-hop 5G IAB systems. The aim of this paper is to revisit and compare these techniques in the context of 5G/6G IAB and with a particular focus on delay. To this end, we formalize the IAB system Integrated Access and Backhaul (IAB) is expected to become a key part of the 5G and future cellular systems enabling cost-controlled network densification. IAB relies upon multi-hop relaying, which makes delay a critical factor, especially for the half-duplex operational regime where only a subset of access and backhaul links can be scheduled simultaneously. Numerous dynamic link scheduling policies were developed in the past for different applications, backpressure being the best known example. Each such policy offers its own balance of supported network throughput, computational complexity and end-to-end delay performance. The latter metric is the least investigated in the literature and is the most important for multi-hop 5G IAB systems. The aim of this paper is to revisit and compare these techniques in the context of 5G/6G IAB and with a particular focus on delay. To this end, we formalize the IAB system