Transmitter Precoding-Aided Spatial Modulation for Secrecy Communications

Precoding-aided spatial modulation (PSM), which conveys information partially by the indices of receive antennas, has some advantages over conventional spatial modulation (SM) using the indices of transmit antennas. In PSM, the precoder may be optimized for different purposes. In this paper, we study the transmitter design in the PSM systems, which motivates to provide secrecy communications. Specifically, we consider a pair of communication terminals overheard by an eavesdropper. The precoder is optimized by jointly minimizing the power received by the eavesdropper and maximizing the power received by the desired terminal. Both the error performance and the ergodic secrecy rate achievable are studied when assuming communications over independent Rayleigh fading channels. Our studies show that positive secrecy rate and low-complexity detection can be attainable simultaneously for the desired receiver even when the eavesdropper employs more receive antennas than the desired receiver.