Research On Physical Layer Security Transmission Technology Of Two-way AF Relay Cooperative Wireless Communication System

Wireless transmission has great challenges to the effectiveness and reliability,due to the openness of the wireless channel,the instability of the wireless network architecture,and the mobility of wireless terminals.Cooperative wireless communication technology,which has emerged in recent years,is a wireless communication technology that has great application prospects.The relay node cooperation improves system transmission performance,at the same time,it also brings new challenges to communication security.The traditional security system based on cryptosystem relies on two important preconditions: one is that the receiver receives the ciphertext information sent by the sender without errors;the other is that the eavesdropper has limited on computing power and can't decrypt information within the security aging.Its application in the future wireless network,especially the edge network,faces enormous challenges.The concept of information theory security(or referred to as perfect security),proposed by the founder of information theory C.E.Shannon,is not limited by the computational capabilities.Based on this,A.D.Wyner proposed that the random characteristics of wireless channels can be used in wireless fading channels to help security transmission and defines the concept of security capacity and lays a theoretical foundation for wireless physical layer security technology.The goal of the security design of the physical layer of the wireless system is to increase the security capacity of the system,and the key of increase of the security capacity is to make the Signal to Interference plus Noise Ratio(SINR)of the legitimate user channel as better as possible than SINR of the eavesdropping channel,so that the eavesdropper's ambiguity of confidential information can be increased as far as possible.This paper takes security capacity as the performance index and introduces new scenarios and new issues when physical layer security design for cooperative wireless communications.This paper focuses on analysis security of three-node Aplify-and-Forward(AF)relay cooperative communication system.The main works of this article as follows:1.In order to enhance the physical layer security performance of three-slot AF two-way relay cooperative wireless communication systems,a relay power allocation/analog network coding scheme is proposed.Firstly,the expression of the security capacity in the basic scenario consisting of a single source node,a single destination node,a single two-way relay node,and an eavesdropping node is deduced,and the excellent relay power allocation scheme about optimization goal for the security capacity in single relay cooperative communication system is proposed.Then,in the case of the ideal channel state information(CSI)is known,the optimal power allocation scheme during the amplifying and forwarding of the bidirectional signal by the relay is calculated,and the scheme is expanded from the single relay cooperative communication system to having multiple relay/multi-antenna cooperative communication system.Simulation results are presented to evaluate secrecy capacity performance of the proposed power allocation schemes for three-phase two-way AF relaying,verified that optimizing the power allocation to the relay node can effectively improve the system security capacity.At the same time,from the simulation results,it is observed that whether or not the power allocation optimization is introduced,the intermediate position between the two legal communicators of relay is most conducive to the secure transmission of the system.And the introduction of the optimal relay power allocation scheme reduced the difference in the secrecy transmission performance brought by different relay positions,that is,the performance of the secrecy capacity obtained by relays in different locations is more consistent,and the restrictions on relay position and channel state changes to the confidential transmission performance of the system are reduced.2.In order to further improve the security performance of the studied three-slot two-relay AF relay wireless cooperative communication system,the idea of adding blocking signal to eavesdropper to increase the receiving fuzziness and a method for combining interference signals with multi-antenna relay beamforming is proposed.In order to overcome the shortcomings of the existing blocking schemes,which need to introduce extra nodes to transmit cooperative blocking signals and have a high system complexity,the first and second time slots(legitimate user transmission time slots)are proposed to emits interference signals by legitimate users.In the third time slot of the protocol,when the relay amplifies and forwards the information received in the first two time slots,it was proposed to use the two beamforming matrices to process the combined bidirectional signals separately,and optimizes each beamforming matrices according to the channel state.By shaping the beamforming matrix in the one hand improve legitimate users reception,the other hand projected the unknown blocking interference signal from the legitimate receiver in the channel zero space.Through joint optimization,the sum of the through puts of the legal communication channels is maximized.Simulation results show that the proposed scheme can significantly improve the system's confidential transmission performance.