Configuration selection and precoder design for spatial modulation in multicast MIMO systems

In this paper, we investigate the configuration (i.e., both mode and antenna) selection and precoder design to improve the multicast multiple-input multiple-output systems employing spatial modulation. We first elaborate the advantages of configuration selection and then propose two selection schemes to maximize minimum Euclidean distance with low complexity. By configuring the selection problem as a tree search problem and adopting tree pruning technique, the first selection scheme attains low complexity while obtaining the optimal solution. In the second scheme, by pruning the less dominant nodes and approximating the signal constellation, the Euclidean distance computation is converted to a simple table look-up operation. Combining this with the first scheme, the second scheme attains even lower complexity without optimality guarantee. Besides configuration selection, the precoder design is investigated, and a precoder design approach is proposed to improve the system. Finally, simulation results demonstrate the efficacy of the proposed approaches in the bit error rate improvement and complexity reduction.