Relay selection scheme for cooperative relay networks with distributed orthogonal space-time block coding

A new orthogonal space-time block coded (STBC) relay selection scheme over wireless cooperative network is presented. A system with four half-duplex relay nodes is considered in particular. We propose two different methods for use in the selection process. In the first method, the four relays are grouped into two subsets of two relays, each having identical encoding process in terms of the construction of extended orthogonal STBC (EO-STBC). The best two relays are selected based on the overall path gain and then Alamouti coding is applied over the selected two relays in a distributed manner. This method improves the system performance with very limited feedback overhead. In the second method, the selection process deals with the four relays as one group and selects the best three relay links based on the overall path gain. This method is shown to achieve better end-to-end bit error rate system performance than the first method but with higher feedback overhead. Simulation results show that the two proposed schemes yield significant improvement in performance over the conventional scheme without using selection approaches.