Distributed Space Time Transmission with Two Relay Selection and Parallel Interference Cancellation Detection to Mitigate Asynchronism

In this paper, we select the best two relays from a set of available relays, each of which is equipped with two antennas, based on the instantaneous path gains. Closed-loop quasi orthogonal space time block coding is then applied over the selected two relays to maximize cooperative diversity. parallel interference cancellation detection is also applied at the destination node to mitigate the problem of imperfect synchronization between the relay nodes. End-to-end bit error rate simulations confirm that the selection scheme yields a significant improvement in performance over the conventional scheme without using relay selection. Furthermore, the bit error rate simulations confirm the advantages of the detection scheme for a range of levels of asynchronism, and that only a small number of iterations is required in the parallel interference cancellation technique.