Mapping Codebook-Based Physical Network Coding for Asymmetric Two-Way Relay Channels

This paper investigates asymmetric two-way relay channels (TWRCs), where a couple of source nodes exchange data with different flow rates via a relay node. A novel mapping codebook-based physical network coding scheme is proposed for improving the performance of such channels. The proposed network coding scheme introduces a mapping codebook that contains several subcodebooks and adaptively selects a subcodebook from the mapping codebook in each data exchange based on the information of signal phase difference. Moreover, distributed transmission power control is also introduced to simplify codebook design and facilitate physical network coding. Simulation results show that it can significantly improve the BER performance as compared to analog network coding. It is also robust to the phase estimation error and the power control error, in particular, in a lower SNR region.