Physical Laver Security In Full-duplex Relay Wireless Cooperative System

Full-duplex technology supports simultaneous transmission of information on the same frequency,which can double the spectrum efficiency in theory and has been one of the key technologies in the future 5G/6G(the fifth/sixth generation)mobile communication system.With the continuous improvement of self-interference cancellation technologies and the demand for high spectrum efficiency,full-duplex relay collaboration has become a hot issue in wireless communications.At the same time,with the large-scale application of wireless cooperative communication network,high throughput and high reliability have become the most basic goals of the development of wireless communication systems,and their security is occupying a more and more important position.Therefore,physical layer security technology of the relay system emerges.This thesis focuses on the physical layer security technology of full-duplex relay system,as follows:Firstly,in the full-duplex relay wireless cooperative network,the physical layer security performance of the optimal relay selection scheme which selects the relay by maximizing the secure capacity is analyzed in detail.The closed-form intercept probability expressions for the optimal relay selection scheme are obtained,in which the relays are using amplify-and-forward and decode-and-forward protocol respectively.The theoretical derivation is verified by numerical and Monte Carlo simulation.The simulation results show that the physical layer security technology based on maximizing the secure capacity is better than the physical layer security technology based on maximizing the main link's capacity,and the intercept probability can be reduced to below 10-5.Secondly,a power allocation scheme is proposed for the four-node eavesdropping model to maximize the secure capacity.The system model is that the eavesdropping node can receive the signals of the source and relay node at the same time.Under the condition that the signal transmission power of the source node and the relay node is separately constrained,the power allocation aims at maximizing the security capacity.Then,the optimal signal transmission power of the source node and the relay node are obtained by using the numerical solution and dichotomy.Finally,the physical layer security performance of the power allocation method is evaluated by the security capacity.The simulation results show that the power allocation scheme proposed in this paper has higher security capacity than the equal power allocation scheme.Under the simulation parameters set in this paper,the secrecy capacity of the proposed power allocation scheme is increased by one time compared with that of the equal power scheme.In this thesis,we study the performance for physical layer security of full-duplex relay system by the relay selection scheme and the power allocation.The research results provide some support for the development of the full-duplex relay system.