Most previous researches on bidirectional relay selection (RS) typicallyassume perfect channel state information (CSI). However, outdated CSI, causedby the the time-variation of channel, cannot be ignored in the practicalsystem, and it will deteriorate the performance. In this paper, the effect ofoutdated CSI on the performance of bidirectional amplify-and-forward RS isinvestigated. The optimal single RS scheme in minimizing the symbol error rate(SER) is revised by incorporating the outdated channels. The analyticalexpressions of end-to-end signal to noise ratio (SNR) and symbol error rate(SER) are derived in a closed-form, along with the asymptotic SER expression inhigh SNR. All the analytical expressions are verified by the Monte-Carlosimulations. The analytical and the simulation results reveal that once CSI isoutdated, the diversity order degrades to one from full diversity. Furthermore,a multiple RS scheme is proposed and verified that this scheme is a feasiblesolution to compensate the diversity loss caused by outdated CSI.
展开▼
