Modified codewords design for space–time block coded spatial modulation

Two kinds of modified codewords for space–time block coded spatial modulation (STBC‐SM) are presented in this study. The first modified codeword introduces a concept of flexible coefficients into the M ‐ary phase shift keying STBC‐SM. A method is proposed to obtain the optimal flexible coefficients. Moreover, the first modified codewords can also be applied to the systems developed from the STBC‐SM. In the second provided codewords, super‐orthogonal space–time trellis codes are applied in STBC‐SM. Therefore, a higher spectral efficiency is obtained compared with the original STBC‐SM. Finally, the simulation results and theoretical analysis demonstrate these performance advantages of the two kinds of modified codewords for STBC‐SM.