On the Buffer Size of Perfect RLNC in Full-Duplex Relay Networks

In the next-generation wireless networks, full-duplex, relaying, and random linear network coding (RLNC) are popular techniques to enhance the network performance such as efficiency and reliability. For full-duplex relay networks, a perfect RLNC scheme known as FBPF (Fewest Broadcast Packet First) was recently proposed and demonstrated a better throughput, or equivalently, expected completion delay performance than the Automatic Repeat Request scheme. However, the original FBPF scheme assumes unlimited buffer and does not take the buffer size into consideration. In this paper, we generalize the FBPF scheme to consider the buffer size as a new parameter. Based on a novel Markov chain model, explicit formulae to characterize the expected completion delay are deduced. Moreover, we present a criterion on the optimal selection of the buffer size under a quality of service constraint, so that the selected buffer size is significantly reduced while the completion delay performance is comparable to the original FBPF scheme with unlimited buffer.