Asymmetric network coding in two-way relay channels for cooperative communications: SER performance and power matching

Network coding in wireless two-way relay (TWR) channels has recently attracted great attentions for its substantial improvement to the performance of network. Especially, its decoding and forward (DF) mode is attractive for its efficiency without noises accumulation. However, most discussions are concentrated in symmetric network coding in the uplink, where a couple of transmitters exchange data with the same modulation type. Besides, the influence of power matching of two transmitters to the performance is rarely mentioned before. This paper investigates the asymmetric modulation network coding in TWR channel. The decision regions for this kind network coding are discussed and the corresponding performances of symbol error ratio (SER) on TWR are deduced. Moreover, power matching is introduced to improve the performance. And the optimum power matching ratio is also derived. The simulation results evaluate the correctness of derived SER expressions in the uplink. And the influence of power matching is also shown.