MAC-layer and PHY-layer Network Coding for Two-way Relaying: Achievable Regions and Opportunistic Scheduling

We consider two-way relay channel with three nodes: two source nodes and one relay in the middle. We characterize the end-to-end rate regions achieved by MAClayer network coding (MAC-XOR) and PHY-layer network coding (PHY-XOR). Noticing that MAC-XOR does not always achieve better performance than pure multi-hopping, we show a simple opportunistic scheduling to achieve the combined region. A similar opportunistic scheduling is also presented for PHYXOR operation. It is shown that the system is stabilized for any Poisson arrivals with rate pair within their respective Shannon rate regions. Moreover, we also present simulation results based on practical cellular system models for both SISO and MIMO cases.