Artificial Noise-aided Spatial and Directional Modulation Systems for Secure Transmission

This paper introduces artificial noise (AN) into the spatial and directional (SDM) system, which combines the benefits of spatial modulation (SM), directional modulation (DM) and AN aided transmission. We first describe the SDM system and introduce AN into the null space of its channel matrix, and then, the bit error rate (BER) upper bounds of both the distributed legitimate user and eavesdropper are respectively derived based on the union bound theory, while the secrecy rate is studied. Simulated results demonstate that the SDM system with the aid of AN, compared with its conventional without AN counterpart, is capable of improving the security over the line- of-sight (LoS) channel encountered. Furthermore, in comparison with the DM-AN counterpart, we show that the spectral efficiency is effectively enhanced.