Research On Directional Modulation Technology In Physical Layer Secure Wireless Communication

The security of the traditional key-based secure wireless communication system relies heavily on the computation complexity of the key and has gradually exposed its potential security risks.However,more fundamental physical layer security(PLS)without complex keys explores the information-theoretical security of wireless transmission.Directional modulation(DM),as an emerging PLS wireless transmission technique,has gained widespread attention in academia and industry in recent years.Its basic idea is to send confidential information to the desired direction while utilizing artificial noise(AN)to interfere the eavesdropping direction.This paper focuses on the design of beamforming algorithms for confidential messages and AN in DM techniques,and the main contents are as follows:1)In order to improve the secrecy sum rate(SSR)of the multiuser MIMO DM system,the leakage-based beamformer is proposed and its basic idea is as follows:confidential information and AN beamforming vectors are designed by maximizing the signal-to-leakage-and-noise ratio(SLNR)criterion,i.e.,maximizing the power of the confidential information in the desired direction and the AN power in eavesdropping region,respectively.The simulation results show that the SSR performance of the proposed method for multiuser DM is superior to the traditional orthogonal method.And with the increase of signal-to-noise ratio(SNR),the SSR performance advantage of the proposed method will be more significant.For example,when the SNR is 15dB,the SSR performance of the proposed method is improved by nearly 40%compared with the traditional orthogonal method.2)To solve the problem that the traditional robust DM needs to obtain the statistical characteristics of angle measurement error,a blind robust DM synthesis without knowing statistical characteristic of error is proposed.The concept of main-lobe-integration(MLI)is introduced to arrange the power of confidential signals to the main lobes of the desired directions,while forcing the power of AN to the main lobes of eavesdropping directions.The simulation results show that the proposed blind robust DM performs better than the existing orthogonal method and leakage-based method in terms of both BER and SSR performance when the angle estimation error exists.With the knowledge of imperfect eavesdropping direction information,the proposed method show about an order-of-magnitude BER improvement over that of the existing methods.3)Aiming at the security risk problem in the traditional DM that the eavesdropper can intercept the confidential information when it moves into the main lobe of the desired direction,a novel scheme of secure precise wireless transmission based on multi-relay cooperation is proposed.In this scheme,multiple relays use the DM technique to make the beamforming main lobes of the confidential information point to the desired location,where the main energy peak of confidential information is formed.The simulation results show that when the eavesdropper is located in the main lobe of the desired direction,the proposed novel scheme of secure precise wireless transmission only achieves the peak received signal-to-interference-plus-noise ratio(SINR)value at the desired position.Due to the random phase,the power in the undesired region is offset each other,and the received SINR is weakened by AN.Finally,the confidential information cannot be recovered in the undesired region.