Distributed STBC for single carrier relay-assisted transmissions over frequency-selective channels

In this paper, we design and analyse a distributed time-reversal space-time block code (D-TR-STBC) that can achieve significant power gain and optimum diversity order in a relay-assisted transmission for single-carrier frequency-selective channels. The idea behind distributed space-time block coding (D-STBC) is to have the relays cooperate in such a way that the signal at the destination is a space-time code, so as to obtain full diversity. In contrast to the literature, we show that the orthogonality of D-TR-STBC can be preserved at the destination by including the signals received via the direct link (from the source to the destination) at the first half of the signalling interval along with the space-time block coded signal received at the second half of the signalling interval. The pairwise error probability (PEP) derivation shows that the proposed scheme achieves the optimum diversity order. Moreover, the symbol error rate (SER) performance of the proposed scheme and competing scheme using different equalization techniques and signal to noise ratios (SNRs) in the source to relay link shows that the proposed protocol outperforms the other by an SNR margin of 2-5 dB.