Physical Layer Security Algorithms With Secrecy Rate Maximization In Cognitive Radio Networks

Cognitive radio(CR) technology is an effective means to improve the efficiency of spectrum allocation,and the unique characteristics of cognitive radio networks make it more security threats than traditional wireless networks,eavesdropping is one of the most important issues.The traditional means of preventing eavesdropping is mainly high level key cryptographic technologies,the main idea of these approaches is that security is ensured based on the limited computational power at the eavesdroppers,therefore, the physical layer security is considered as a complementary approach to get a high degree of attention.This thesis puts the system of secrecy rate(Secrecy Rate) maximization as the target,combining with multi-antenna and cooperative relay technology,to analyzethe physical layer security in cognitive radio networks(CRN).The main works of this thesisareas follows:In the cognitive radio network(CRN) with multiple multi-antenna eavesdroppers, in order to satisfy the requirement of the physical layer security, this thesis applies the optimization design of the transmit covariance matrix of the secondary users toimprove the security performance ofthe physical layer. To maximizethe system security rate, first of all, this thesisdiscussesthe secrecy rate constrained(SRC) problem. On this basis, using the matrix properties and Charnes-Cooper transform, we make that equal to a problem of semi-definite programming(SDP) and get the transmit covariance optimization of SU by SDP. Finally, this thesisworks outthe optimization scheme of physical layer security in cognitive radio networks with multiple eavesdroppers, and the analysis of the time complexity of the algorithm is analyzed. Simulation results show that compared with the existing sub-optimal transmissiondesigns, the proposed method improves the secrecy rate and has more advantages on the complexity.Multiple eavesdroppers can collusion with each other in order to better tap information,it is more hidden and more security threats in the cognitive radio relay networks.For the cognitive relay networks with multiple collusion eavesdroppers, this thesis proposes a design and optimization of the physical layer security transmission scheme of null-space artificial noise and amplify-and-forward(AF) base relay beamforming. First of all, modeling the system and it is designed as a security rate maximization problem.Secondly, through the introduction of a slack variable, the secrecy rate maximization problem can be converted to the problem of tight relaxationis proved in theory. Further, joint optimization for the relay beamforming weighting matrix and the artificial noise covariance matrix based on semi-definite programming. At last, simulation results indicate thatthe design is verified can greatly improve the system security rateby using MATLAB tool.