Research On Physical Layer Security For Full-Duplex Two-Way Relaying Networks

The full-duplex two-way relay system,which completes signals exchange at the same time and frequency,saves time slot and frequency resources and has become one of the important research contents of 5G mobile communication system.At the same time,due to the broadcast characteristics and open nature of wireless transmission,the transmission signal is easily to be eavesdropped,and the security of wireless transmission is attracting more attention.As the underlying security technology,physical layer security only uses the randomness of the channel to improve system security,which can be used as a guarantee for high-level protocol encryption algorithms.This paper studies the physical layer security of full-duplex two-way relaying networks,and the main contents are shown as follows:Firstly,in the presence of a passive eavesdropping node,a relay selection strategy is used to improve the secrecy performance of a full-duplex two-way relaying system with multiple Amplify-and-Forward(AF)relay nodes.The optimal relay node is selected by maximizing the system security capacity,and the closed-form expression of secrecy output probability is analyzed in this paper.The comparison between the numerical simulation and the Monte Carlo simulation verifies the correctness of the theoretical derivation,and shows that the full-duplex relay system based on the optimal relay selection strategy has higher secrecy performance than the traditional single-relay system and the half-duplex system.Secondly,for the full-duplex bi-directional multiple input multiple output(MIMO)relaying system,in the case of a potential eavesdropping node,a new joint precoding and cooperative interference strategy is proposed to improve the secrecy performance of the system.The strategy assumes that the eavesdropping channel state is unknown,and the AF relay node transmits an artificial noise(AN)signal to interfere the eavesdropping node while forwarding signals.This paper designs AN to minimize the impact on the transmission of the main link,designs user precoding to achieve the equivalent channel of eavesdropping with unsatisfactory rank,weakens the performance of eavesdropping nodes,and on this basis,achieves the maximum capacity of the main link through joint optimization of precoding matrix and AN matrix.Based on the idea of genetic algorithm,the joint optimization solution of precoding and AN design is obtained by iteration for many times under the transmission power limitation of nodes.The simulation results show that the joint optimization strategy proposed in this paper effectively improves the security performance of the full-duplex two-way MIMO relay system compared with the traditional strategy.In conclusion,this paper studies the secrecy performance with relay selection,precoding and cooperative interference strategies in the full-duplex two-way relay systems,which provides theoretical support for the improvement of the physical layer security of the system in the future,and has promising applications value.