Research On Physical Layer Security Transmission Technology Based On Direction Modulation In Wireless Networks

Physical layer security technology can effectively improve the security of wireless information transmission,and form the double guarantee of wireless transmission together with traditional encryption technology.Directional modulation,as a novel physical layer security technique,utilizes the difference between the primary channel and the wiretap channel to achieve secure transmission.The main contributions of this paper are as follows:(1)For directional modulation broadcast systems,a robust synthesis scheme with high performance based on maximizing signal-to-leakage ratio(Max-SLNR)and maximizing signal-to-artificial-noise ratio(Max-SANR)is proposed.The beamforming vector for the confidential information is designed to preserve its power as possible in the desired receiver by minimizing its leakage from transmitter to eavesdropper,while the projection matrix of artificial noise(AN)is to minimize the interference of AN at the desired receiver.Simulation results show that compared to orthogonal projection(OP)method,the proposed robust Max-SLNR plus Max-SANR achieves better secrecy rate(SR)and bite-error rate(BER)performance along the desired directions,which obviously enhance the security of the systems.For a given SNR 30dB,the proposed robust method can achieve not only about thirty percent improvement on SR but also one order of magnitude BER enhancement along the desired directions.(2)In view of the potential security issue caused by the fact that the transmitted beam in conventional directional modulation system only has angle dependence,in order to solve the problem,a new idea of precise and secure transmission is proposed.Through the three key technologies of random subcarrier selection,directional modulation and phase alignment,the transmitted beam forms a two-dimensional dependence of the angle-distance.The scheme achieves a fast coherent combining via discrete Fourier transform,which greatly reduces the receiver complexity.The signal-to-interference-and-noise ratio(SINR)and security rate are derived theoretically.Also the upper bound of SINR in the wiretap area are attained.Simulation results show that the proposed scheme actually can achieve a single SINR peak on the small neighboring region around the desired receiver.By Monte Carlo simulation,the derived theoretical formula of average SR is verified to coincide with the exact results well for medium and large scale transmit antenna or in the low and medium SNR regions.