Performance of Relay Selection Schemes for Cooperative OFDM Space-Time Diversity Systems

This paper focuses on relay node selection schemes and maximum ratio combining method (the RNS/MRC schemes) for OFDM based space-time coded cooperative systems. Specifically, two cooperating relays among the available relays are first selected for Alamouti space-time coded transmission using the decode-and-forward protocol. Assuming that perfect channel knowledge is available at the destination, two relay selection criteria are derived aiming to minimize the outage probability and the upper bound of average symbol error rate, respectively. Then, the direct link and the cooperating link are combined at the destination using the MRC method. Numerical results demonstrate that the RNS/MRC schemes could achieve full diversity order, as if all the nodes were used.