Beamforming based decode-and-forward cooperation via backward synchronization

In this paper, a beamforming (BF) based cooperation scheme with decode-and-forward (DF) protocol is proposed and its performance analysis is provided. Firstly, to solve the issue of carrier synchronization in distributed networks, a backward synchronization (B-Sync) method is introduced, where participating relays synchronize to the reference carrier broadcast by the destination and make signals superimposed coherently at the destination without any phase feedback. Then, based on B-sync, a cooperation scheme with DF protocol is proposed to carry out BF forwarding among relays. The outage probability of this scheme is derived and analyzed, which shows that the full diversity order can be achieved by the proposed scheme. Furthermore, symbol error probability (SEP) analysis is presented to evaluate the practical performance. Simulation results validate the analysis, and show that the proposed scheme outperforms other existing ones in terms of outage probability and SEP.