Physical Layer Security Of MIMO Systems Based On Hybrid Duplrx Relay And Beamforming

With the development of wireless communications technology,especially the evolution of 4G to 5G,higher security is required.Due to the openness and broadcast ability of the transmission medium,wireless communication causes legitimate user information in the wireless network to be attacked by potential illegal users,which poses a great threat to the security of wireless communication.The traditional cryptography-based related encryption technology needs to continuously improve the computational complexity of password cracking,which has many drawbacks.Physical layer security can realize the security guarantee by using the uniqueness and dissimilarity of wireless channels,which can greatly enhance the security system of the whole system.As a key technology of wireless communication,MIMO technology can use the degree of freedom of space to obtain the gain of diversity and multiplexing,and improve the transmission rate and reliability of the system.In recent years,FD relay cooperation technology has become a research hotspot of wireless communication,and the corresponding security problem is also one of the hot issues at present.The safety performance of the FD system is higher than that of the HD system,but the safety rate of the FD system is subject to self-interference.In the case of strong self-interference,the secrecy rate may even be lower than the HD system.The complexity and energy consumption of self-interference cancellation is high.Therefore,this dissertation proposes an adaptive FD/HD hybrid duplex relay scheme to dynamically select the duplex mode without the complex FD self-interference cancellation,which maximizes the system's secrecy rate.Firstly,a MIMO relay system model with hybrid relay is established.At the same time,the beamforming technology is used at the transmitter and relay to improve the security performance of the system.Taking the security rate as an indicator,due to the influence of residual self-interference in the FD system,the hybrid duplex relay scheme enables the relay to select the relay mode in the FD and HD modes to maximize the secrecy rate of the system while maintaining relatively low computational complexity.The MIMO relay communication using AF protocol is analyzed,and the hybrid duplex relay scheme is studied.The secrecy rate of the hybrid relay system is improved by designing the beamforming matrix of the transmitter and the relay.In order to reduce the computational complexity,the vector problem is transformed into a scalar problem by SVD.Due to the non-convexity of the objective function,a suboptimal iterative power allocation algorithm based onDC programming is proposed.Under the limitation of the total transmit power,the proposed problem is solved by using the proposed transmitter and relay power allocation algorithms.The simulation results show that the proposed hybrid duplex relay scheme can achieve a better security performance than the traditional FD or HD relay system.The proposed power allocation algorithm has a faster convergence rate and reduces complexity.Firstly,the channels and signals of the system under DF protocol are modeled and analyzed,and the beamforming matrix of the transmitter and relay is designed to improve the security performance of the system.In this study,the secrecy rate in different duplex relay communication systems under AF and DF protocols is simulated.The simulation results show that the hybrid duplex relay scheme used in the DF protocol system can effectively improve security.At the same time,the secrecy rate of the DF protocol is higher than the AF protocol regardless of the duplex mode.