A cooperative diversity scheme based on differential space-time codes for correlated rayleigh channels

Abstract

In this paper, we present a novel cooperative diversity protocol with distributed differential space-time block coding which can achieve full diversity and full rate with no need of channel state information (CSI). A close form expression for bit error rate (BER) of the proposed scheme is derived for temporal correlated Rayleigh channels without considering the decoding errors between interusers. In traditional differential space-time block coding scheme, difference is done on each whole block. As to distributed cooperative diversity scheme, traditional difference is not practical for the perfect information of the whole block is unknown to each user when to be differential encoded. In our differential modulation scheme, the information of the two cooperative users is modulated to orthogonal real axes and image axes. This degrades joint block difference to independent difference, which makes the full rate transmission possible. The proposed transmission scheme is analyzed for different channels of interusers and channels from interusers to destination. Numerical results show that performance of the proposed scheme gets distinct diversity gain and coincides with the analytical results well