Research On Physical Layer Security Of Cognitive Relay Networks Based On Cooperative Jamming

With the demand for communication services is increasing greatly in the era of information,the contradiction between the scarce spectrum resources and the low utilization rate is becoming more and more intense.To solve this problem,cognitive relay network has emerged,which combines the cognitive radio and the relay cooperative technology,it can not only improve the spectrum utilization,but also broaden the coverage area of wireless.However,due to the inherent openness and broadcasting characteristics of wireless communication,it is prone to be threatened by security threats,such as eavesdropping and interference.In particular,these threats are greater in the transmission of cognitive relay network,the traditional link layer security mechanism can not deal with these security threats fundamentally and protect the security of wireless communication systems.Physical layer security can improve the security performance of the network by exploiting the physical and interference characteristics of wireless channels,it has great potential to solve the security problem of wireless communication.This paper mainly studies the physical layer security in cognitive relay networks.This dissertation carried out the following two aspects of research by introducing cooperative jamming:Focusing on the problem of secure transmission in cognitive relay network with trusted relay,a physical layer security scheme based on jointly optimal transmission relay and interference relay selection is proposed.The cooperative transmission relay and cooperative interference relay are optimized to realize the secure transmission of information,this work derives closed-form expressions of the secrecy outage probability of the proposed scheme under condition of rayleigh fading channels,and carries out lots of experiments on this basis.Numerical results show that the jointly optimal transmission relay and interference relay selection scheme can achieve lower average secrecy outage probability in different scenarios,and improve the security performance of cognitive radio networks.Aiming at the problem of secure transmission in cognitive relay network with untrusted relay,a physical layer security scheme based on the transmission with destination performing cooperative jamming is proposed.In order to improve the efficiency of energy utilization of the system and reduce energy consumption of operation,the relay nodes have the ability to collect energy from the radio frequency signal by introducing energy harvesting technology.This work achieves the secure transmission of information through finding the optimal coefficient under power splitting policy and time switching policy.The security performance of the proposed schemes are studied,this work derives analytical expressions of the secrecy outage probability of the proposed schemes under condition of rayleigh fading channels.Numerical results show that the power splitting policy achieves lower secrecy outage probability than that of time switching policy at higher tolerable interference of primary network and target secrecy rate.