Research On Transmission Technology For Ensuring The Security Of Cooperative Relay Networks

With the rapid development of wireless communication networks,information transmission rate has been greatly improved.However,the security of information transmission is also under threat because of the complicated network structure.The cryptography based on the traditional secret codes system is only able to improve the information security performance to a certain extent.Furthermore,the traditional cryptography technology also faces great challenges due to the rapid development of the computational capability of computers.Therefore,the research of physical layer security has been widely concerned by researchers.At the same time,many research results show that the cooperative relay networks have the advantages of improving the system capacity and increasing the signal coverage.However,under the influence of the complex networks structure,the existing of multi-node,the openness of the system and other features,the security of information transmission is vulnerable to be threatened.Fortunately,the physical layer security technology combines the spatial characteristics and time-varying characteristics of the radio channel and can be used to secure the information transmission of the cooperative relay networks.This paper proposes and analyzes the cognitive relay network security technology under the assumption of Rayleigh and Nakagami channel.And also the cooperative relay network security combined with the energy harvesting technology has been researched.In the above two researches,with the joint application of cognitive relay networks and spectrum sharing technology,the relay node with adaptive DF protocol chooses the forwarding node according to opportunistic relay selection strategy.Then,we derive the exact closed-form expressions of the non-zero secrecy capacity probability and the exact secrecy outage probability(SOP).Moreover,we analysis the asymptotic performance of the SOP in two special cases.The third research is to combine the cooperative relay network with the wireless energy harvesting technology,and propose a secure transmission protocol based on time switching energy harvesting technology.It is reasonable to use full duplex technology and cooperative jamming technology to ensure the safe transmission of information.Therefore,we derive the expression of secrecy throughput,and we also deduced the expression of outage probability and intercept probability according to the security-reliability trade-off analysis.The results of the analysis are simulated by MATLAB platform.The results show that,based on the research of cooperative relay network and spectrum sharing technology,the cognitive relay network can improve the security performance by increasing the peak interference power constrain of primary users and expanding the secondary network scale.Moreover,outdated channel state information has a significant detrimental effect on the secrecy performance.With the research of cooperative relay network security combined with energy harvesting technology,it can be found that the secrecy throughput increases firstly and then decreases with the increasing of time switching factor.The optimal value of time switching factor can be found by exhaustive search method.