Wireless Bidirectional Relaying using Physical Layer Network Coding with Heterogeneous PSK Modulation

摘要

In bidirectional relaying using Physical Layer Network Coding (PLNC), it isgenerally assumed that users employ same modulation schemes in the MultipleAccess phase. However, as observed by Zhang et al., it may not be desirable forthe users to always use the same modulation schemes, particularly whenuser-relay channels are not equally strong. Such a scheme is calledHeterogeneous PLNC. However, the approach in [1] uses the computationallyintensive Closest Neighbour Clustering (CNC) algorithm to find the networkcoding maps to be applied at the relay. Also, the treatment is specific tocertain cases of heterogeneous modulations. In this paper, we show that, whenusers employ heterogeneous but symmetric PSK modulations, the network codingmaps and the mapping regions in the fade state plane can be obtainedanalytically. Performance results are provided in terms of Relay Error Rate(RER) and Bit Error Rate (BER).