Network Coding for Two-Way Relaying Networks Over Rayleigh Fading Channels

Wireless network coding is a useful technology that can increase the total throughput of wireless networks. There are, however, few works focusing on wireless network coding over fading channels, which is an important characteristic of many real wireless channels and may result in performance degradation. To investigate the fading channel's impact on network coding, based on the constant transmission power scheme and the channel inversion-transmission scheme, we analyze network throughput over Rayleigh fading channels. It is shown that, when the difference between average channel gains over two broadcasting channels is very large, the throughput of network coding greatly decreases, and the advantage of network coding almost disappears. To address this issue and to maximize the throughput of network coding over fading channels, we formulate the fading compensation for network coding as optimization problems and present the optimal transmission data rate and transmission power level of the relay node. Furthermore, to consider the realization problem of network coding over fading channels, including unbalanced traffic load and asynchronization of packet arrivals, we present two opportunistic optimal network coding (OONC) schemes. Performance evaluation has shown that the proposed opportunistic schemes perform well in various scenarios.