MQAM space-time block coding with differential detection

On the basis of analyzing of some existing differential space-time coding (DSTC) schemes, we develop a differential space-time block coding scheme based on multiple levels quadrature amplitude modulation (MQAM) in this paper. By introducing MQAM, the developed scheme can avoid the performance loss of conventional DSTC schemes based on MPSK modulation due to the decrease of minimum distance between constellation symbols in high spectrum efficiency. Compared with the existing DSTC schemes, the developed scheme has lower computational complexity and simple decoder. Moreover, it can achieve higher code rate in the case of more than two transmitter antennas. Theoretic analysis shows that the scheme has higher coding gain than existing differential unitary space-time coding scheme and differential orthogonal space-time coding scheme, and corresponding simulation results also show that our scheme has lower bit error rate (BER) when compared with the above two schemes.