Based on orthogonal space-time block code

a scheme for constructing unitary space-time code is proposed.The conclusion that the proposed scheme can achieve full diversity is proved.Compared with original scheme

the advantage of proposed scheme is its higher code rate.However

the disadvantage of proposed scheme is its high complexity needed for decoding.In view of high complexity of the optimum decoding algorithm a suboptimal decoding algorithm is employed.The complexity of suboptimal algorithm is almost the same as the fast decoding algorithm of original scheme.Monte-Carlo simulation shows that the required SNR of the proposed scheme is reduced by 5dB relative to original scheme at the same BER and spectrum efficiency.Meanwhile

simulation results indicate that the SNR of the suboptimal algorithm loses about 1dB compared to that of the optimum algorithm.