Cooperative Network Coded ARQ Strategies for Two-Way Relay Channels

In this paper, novel cooperative automatic repeat request (ARQ) methods with network coding are proposed for two-way relaying network where two communicating nodes are assisted by a relay node at the cooperative retransmission phase upon failed transmission of a packet. The proposed approach integrates network coding into cooperative ARQ (C-ARQ), aiming to improve the network throughput by reducing the number of retransmissions. For successive retransmission, three different methods for choosing the retransmitting node are considered. The throughputs of the methods are analyzed and compared. The analysis is based on a binary Markov channel, which takes the correlation of the channel coefficients in time into account. Analytical results show that the proposed use of network coding enhances throughput performance up to 15% compared with C-ARQ without network coding and 40% compared with traditional ARQ when the relay channel conditions are better than the direct channel between two communicating nodes. It is also observed that correlation can have a significant effect on the performance of the proposed cooperative network coded ARQ (C-NC-ARQ) approach. In particular, the proposed approach is advantageous for moderately fast to slow fading channels where channel correlation coefficient varies from 0.5 to 1.