Physical Layer Security On Millimeter-wave Using Digital Beamforming

As the demand for the mobile communication system grows rapidly,the limitations of the 4G network are becoming more and more apparent,which has led to the development of the 5G system.To meet the bandwidth requirements of the 5G system,millimeter-wave communication is proposed to be used.However,it is difficult to apply it to cellular networks because of the severe path loss.A massive antenna array is needed to overcome this difficulty.Fortunately,it is possible to deploy a massive antenna array on a small scale because of the short wavelength of the millimeter-wave.The digital beam forming(DBF)is a technique of using digital methods to implement beamforming.Due to the baseband reserves all the information of antenna signal,digital beamforming can adopt advanced digital signal processing technology for antenna array signal,which can significantly improve the performance of antenna array.But because of the high cost of transmitting and receiving components,hybrid array becomes a compromise option.This paper studies the millimeter-wave line-of-sight(LOS)relay communication model,based on a LOS wiretap channel,and researches the influence of baseband precoding and artificial noise to communication security.This paper researches three aspects of problems:The first is digital baseband precoding based on an equivalent channel model.Based on an equivalent channel model,the appropriate precoding matrix is generated,which can be used to reduce the eavesdropper's reception and increase the secrecy rate.In addition,based on the features of the rician channel,this paper presents a baseband precoding scheme based on the LOS channel,which reduces the requirement of the channel states information(CSI).The second is artificial noise based on a random factor.According to the channel characteristics,the appropriate artificial noise that is applied to the signal after precoding can only affect the receiver's reception.In addition,this paper puts forward a random factor of artificial noise,the noise of constellation diagram for legitimate recipient translation,does not affect the receiving signal,at the same time makes the eavesdropper cannot recover the right signals.The last is a security research on multi-user multi-eavesdropper communication.In this section,this paper studies the baseband precoding under multi-user condition and the artificial noise under multi-eavesdropper condition,and simulates the performance of these two schemes.