Research On Physical Layer Security Transmission Technology Based On Arrays

The research on multi-antenna technology brings opportunities for the development of physical layer security（PLS）technology.In addition to providing rich physical channel resources for wireless communications,the applications of pre-coding,antenna selection,Beamforming（BF）and other techniques in multi-antenna technology also significantly improve the quality of communications,and create possibilities that the main channel is better than the wiretap channel.By exploiting the degree of freedom in the spatial domain provided by multiple antennas,the transmitter equipped with multiple antennas is capable of protecting the transmit signal in the null space of the wiretap channel from being obtained by the eavesdropper even in close proximity.This paper is mainly focused on the simulation and implementation of the PLS technologies based on antenna arrays,including improving angle-domain security using phased array（PA）,and the baseband implementation of range-domain PLS system.Finally,array technology is introduced into the system to obtain the simulation results of spatial position based secure communication.Firstly we investigate the angle-domain PLS based on PA and propose a directional modulation scheme based on antenna subset（ASDM）.Although the computational complexity of traditional antenna subset modulation（ASM）is lower than that of traditional directional modulation（DM）,its bit error rate（BER）performance is worse than that of DM.Therefore,the ASDM proposed in this paper can improve the BER performance while ensuring high security level.In addition,we analyze the essential similarities and differences among ASDM and traditional BF,ASM and DM and highlight the advantages of ASDM.Specifically,compared with traditional ASM,our method is better than traditional ASM in terms of BER performance;At the same time,ASDM,under some particular circumstances,can be regarded as a special case of DM,and acquire degree of freedom in antenna weights design e.g.generating dynamic interference in the unexpected direction to enhance security while maintaining the same BER performance as traditional DM with lower complexity when the target direction constantly changes.Finally,on the basis of ASDM,the BER performance is further improved by antenna subset selection.Simulation results show that the improvement of performance is particularly obvious when the number of antenna subset is small.Furthermore,to overcome the time-variance of FDA and achieve range-domain PLS,we establish a PLS system based on FDA single-antenna multi-carrier architecture.The PLS system can realize range-domain security,and the results of field tests in the LoS and NLoS multipath environments are consistent with the simulation.Specifically,the correct constellations can be recovered at the legitimate receiving position,but deteriorates dramatically when the receiver is away from the legitimate position.This feature ensures the secure communications between the transmitter and the legitimate receiver.Finally,the proposed range-domain PLS system is integrated with array technologies,and simulation results show that the system can achieve position-based security.