A Low-Delay Hybrid Half/Full-Duplex Link Selection Scheme for Cooperative Relaying Networks

In this paper, we propose a hybrid half-duplex (HD)/full-duplex (FD) link selection scheme for cooperative buffer-aided (BA) relaying networks with small buffers. FD BA relaying offers high spectral efficiency but it does not change the buffer states, while HD relaying offers the ability to change the buffer states, which can be exploited to minimize the outage probability and the average delay by controlling the queue length of the relays. Unlike the existing hybrid BA relaying schemes and opportunistic relying schemes, the proposed scheme considers the average buffering delay and uses probabilistic relay selection (RS) instead of using a fixed RS policy. It probabilistically prioritizes the selection of one of the FD and HD modes over the other. Markov chain (MC) theory is used to model the considered system and derive the throughput, average delay and outage probability as functions of the prioritizing probabilities. Based on the buffer and average channel states, the prioritizing probabilities are determined such that the overall average delay is minimized using the accelerated proximal gradient method. As compared to the existing HD, opportunistic, and hybrid BA relaying schemes, simulation results show that the proposed scheme offers higher throughput and lower average delay.