Performance Analysis of SM-Index Modulation Based Cooperative Wireless Communication System

Cooperative communications with spatial modulation (SM) scheme have been studied for high speed and reliable wireless transmission systems. For common SM technique, the transmit antenna is selected by the input information bits randomly. However, the real channel condition corresponding to the active antenna determines the performance of SM system directly. SM-index modulation (SM-IM) scheme can modulate the index of the active transmit antenna and the modulated SM symbol into a new transmit symbol, which can be employed to get rid of the poor channel conditions' impact on the performance of SM systems. To further improve the system performance, we propose a cooperative communication system based on SM-IM scheme in this paper, which can avoid the disadvantages of the poor channel allocation of the cooperative SM system. Closed-form expression of the average bit error rate (BER) of the proposed SM-IM cooperative system is derived. Simulation results and analysis show that the proposed scheme outperforms the typical dual-hop SM cooperative system significantly.