Optimal Power Allocation in Spatial Modulation Systems
Abstract: In spatial modulation (SM) systems, when channel state information is available at the transmitter, adaptive power allocation can be exploited to enhance the SM performance. In this paper, optimal power allocation in SM systems is considered from an information-theoretical theoretical view. First, as there is no closed closed-form expression of the SM capacity, the instantaneous mutual information is formulated in an analytic form for SM systems with two transmit antennas. Then, two powerpower allocation algorithms are proposed to maximize the SM mutual information. One is a sub-optimal power-allocation allocation algorithm that is established in closed form to maximize the upper bound of SM mutual information. The other is an iterative algorithm for optimal power allocation that is proposed to achieve the maximum mutual information of SM systems while dramatically reducing the operational complexity compared with global computer searching. To evaluate the performance of the proposed power power-allocation allocation algorithms, numerical and simulation resultss are reported in terms of outage capacity and ergodic capacity, which demonstrates that the proposed power-allocation power allocation algorithms significantly improve the SM performance, compared with conventional equal-power equal allocation.