A Low-Delay Lyapunov-Based Relay Selection Scheme in Buffer-Aided Cooperative Networks

In this letter, we propose a hybrid half-duplex (HD)/full-duplex (FD) relay selection (RS) scheme for buffer-aided (BA) cooperative relaying networks with small buffers that enjoys the adaptability of the Lyapunov optimization framework. The proposed scheme minimizes the overall average delay by controlling the buffer lengths and optimizing the nodes' transmission rates. Due to the separable structure of the formulated problem, the imposed delay by the potential relays is assessed independently, and the relay that causes the least delay is selected. As compared to the existing HD, opportunistic, and hybrid HD/FD BA relaying schemes, simulation results show that the proposed scheme offers a lower average delay if adaptive transmission rate is used. Also, it offers a lower delay at most signal-to-ratio (SNR) regions if fixed rate is adopted.