Directional modulation based on chaos scrambling and artificial noise for physical layer security enhancement

Directional modulation (DM), as an emerging promising physical layer security (PLS) transmission technique for wireless communications, has attracted much attention over the past decade. It endows transmitters the ability to directly transmit the confidential messages to legitimate receivers along with pre-specified directions while distorting signal waveform signatures projected along all other spatial directions to guarantee the security of information transmission. Traditional DM designs are based on the assumption that eavesdroppers (Eves) and legitimate users (LUs) are in different directions. Nevertheless, it is not always the scenario in practical applications, as it is possible that Eves and LUs are in the same directions or even at the same positions, which results in that signals received by Eves will be approximately the same as LUs'. To address this problem, the chaos scrambling (CS) technique is employed in this paper. A DM technique based on CS and artificial noise (AN) is proposed for PLS enhancement. The symbol error rate, secrecy rate, and robustness of the proposed CS-AN-aided scheme are analysed and simulated. Simulation results show the effectiveness of the proposed method and the PLS can also be guaranteed even if Eves are aligning with the desired directions or very close to the LUs.