Differential orthogonal space-time coding with star-QAM

By using star-quadrature amplitude modulation (star-QAM), a multiple amplitudes differential orthogonal space-time coding scheme is proposed. The scheme can avoid the performance loss of conventional differential space-time coding (DSTC) schemes based on PSK modulation in high spectrum efficiency via multiple amplitudes modulation. Compared with conventional PSK based DSTC schemes, the proposed scheme has higher spectrum efficiency by carrying information not only on phases but also on amplitudes, and has higher coding gain. Moreover, the scheme has simpler decoder, and higher code rate in the case of more than two antennas. The simulation results also show that our scheme has lower BER when compared with existing differential unitary space-time coding and differential orthogonal space-time coding schemes.