Optimal Spatial-Domain Design for Spatial Modulation Capacity Maximization

As a promising technique in multi-antenna systems, spatial modulation (SM) introduces the spatial domain into its constellation by mapping more information with antenna selection, in addition to the signal domain. To further improve the capacity performance of SM, an iterative algorithm for the spatial-domain design is proposed in this letter, where the optimal probability of activating each transmit antenna is obtained to maximize the instantaneous capacity of SM. By comparing the metrics of outage and ergodic capacity with the conventional SM, illustrative numerical results not only demonstrate the throughput achieved in the proposed scheme, but also substantiate the domination of the proposed scheme over the conventional SM.