Research On Physical Layer Security Precoding Techniques Of Massive MIMO

Massive multiple-input multiple-output(Massive MIMO)technology is one of the core technologies of the fifth generation wireless communication system.Without increasing the transmission power,signal bandwidth or cell density,it can increase the regional throughput by two orders of magnitude or even more antennas than the traditional MIMO technology,so as to meet the growing needs of various wireless applications.However,due to the open nature of wireless systems,Massive MIMO system is vulnerable to eavesdroppers and interference.In order to deal with these security risks,encryption and decryption algorithms are generally used,and high-level secure transmission protocol is used to achieve secure transmission.However,encryption technology brings high computational complexity and high hardware requirement on both sides of transmission.As a supplement to high-level security technology,physical layer security technology has attracted the interest of researchers in recent years.Physical layer security technology can increase the difference between legitimate channel and eavesdropping channel by using beamforming and transmitting random noise,so as to enhance the confidentiality of communication system.According to the wireless transmission conditions in urban areas,this paper establishes the physical layer security model of Massive MIMO system,and applies the physical layer security technology such as artificial noise precoding and downlink power allocation to the established model to analyze their effects on the system security performance.Firstly,the physical layer security model of Massive MIMO system is established,and the existing linear data precoding technology is analyzed.They are introduced into the physical layer security model.The improvement of system security performance and the suppression of eavesdroppers by different data precoding technology are analyzed.The relationship between the number of base station antennas and the system security performance is discussed.In order to select an appropriate power allocation matrix for data precoding,this paper adopts a power allocation algorithm based on maximizing the channel capacity of legitimate users,and then simplifies the algorithm.The simplified algorithm is compared with the average power allocation scheme,and their effects on the system security performance are analyzed.Secondly,this paper studies the artificial noise precoding technology in physical layer security technology,and introduces it into the established security model.The effects of different artificial noise precoding matrices on eavesdropping suppression and confidentiality are analyzed.Finally,in order to evaluate the impact of artificial noise on eavesdroppers,two power allocation methods are proposed: one is to maximize the ratio of legitimate channel capacity to eavesdropping capacity,the other is to consider the maximum security energy efficiency of communication confidentiality and eavesdropper suppression simultaneously.The two schemes are compared with the average power allocation scheme by simulation.The performance of the two power allocation schemes is verified from transmission and eavesdropping suppression aspects.