Research On Secure Beamforming Of Millimeter Wave Multi-antenna System

The fifth generation mobile communication system(5G),which is characterized by higher data throughput and faster data transmission rate,has officially entered the commercial stage.Millimeter wave communication has become an important part of 5G communication technology because of its rich spectrum resources.However,the security of data transmission and the protection of user privacy are still important issues for users.The physical layer security technology based on information theory mainly uses the inherent randomness of wireless channel to ensure secure communication.It does not need complex encryption/decryption algorithm and has high scalability,so it is more suitable for 5G network.At present,the research on the physical layer security of millimeter wave communication focuses on the passive eavesdropping scenario,while the research on the physical layer security of millimeter wave communication based on the active eavesdropping scenario is less.In view of the above problems,this paper mainly focuses on the physical layer security of millimeter wave multi-antenna system,which is divided into three aspects:First of all,considering the high directionality of millimeter wave communication,which has a certain natural resistance to eavesdropping,the eavesdropping performance limit of millimeter wave communication system in passive/active eavesdropping scene is quantitatively deduced from the beam dimension.The analysis shows that when some parameters of the system(such as eavesdropping distance or deviation angle)exceed the eavesdropping threshold,there is still a risk of eavesdropping in millimeter wave communication,which shows that it is still necessary to study the security problems in millimeter wave communication.Then,aiming at the millimeter wave communication system with active eavesdropper,considering the propagation characteristics of the millimeter wave multi-antenna system,a scheme of artificial noise assisted safe beamforming without complex zero space calculation is adopted to resist eavesdropping,and the power allocation scheme to maximize the secure capacity of the system and minimize the secure interruption probability of the system is derived respectively.The simulation results show that the scheme can improve the security performance of millimeter wave system with active eavesdropper.Finally,this paper considers a more complex eavesdropping scenario,that is,there is more than one eavesdropper in the millimeter wave communication system.Under the condition that there is error in the state information of the legal link channel,the paper studies the use of artificial noise to realize the safe transmission of the millimeter wave multi antenna system,and studies the power allocation scheme to maximize the safe capacity of the system under the constraint of the safe interruption probability.The simulation results show that the artificial noise can improve the security performance of the system.When the channel estimation error increases,to improve the security capacity of the system,more power needs to be allocated to transmit the artificial noise signal.