Phase rotation-based precoding for spatial modulation systems

In this study, the authors investigate the benefits of phase-rotation-assisted precoding (PRP) technique in spatial modulation (SM) systems, which are based on maximum free distance d_min. First, a closed-form solution of the maximum-d_min PRP matrix is derived for the scenario of having two transmit antennas (N_t = 2). Moreover, two numerical methods are proposed for dealing with the case of N_t > 2. The complexity of the proposed algorithms is presented. The authors simulation results show that the proposed PRP algorithms provide beneficial bit error ratio performance improvements compared with both the conventional SM and with the existing adaptive SM.