Research On Physical Layer Security Agorithms With Relay Collaboration In Cognitive Networks

Cognitive radio technology is one of the key technologies to relieve the shortage of spectrum resources and improve the utilization of spectrum efficiency.However,the sharing and openness characteristics of cognitive radio network face more security threats.Hence,the secure technology is increasingly more and more important.The main technique of traditional information security technology is high-level encryption technology.Along with the advance of science and technology,the computer's computing power also get rapid ascension.The traditional encryption technology will face serious challenge.Therefore,the physical layer security has gained the wide attention of scholars from domestic and overseas.This thesis sets the secrecy rate as the indicator of system security.Combining the cognitive radio technology and cooperative relay technology,this thesis launches the radio network with relay coordination in the physical transmission scheme for security.And the main tasks are summarized follows:Aimed at physical layer security transmission problem under cognitive radio network equipped with multiple secondary pairs and multiple relay,the study of it is more complex than the existing system that with single secondary user pair and single relay in terms of the theoretical analysis and optimization.In this thesis,the goal is to maximize the worst joint secrecy rate of secondary users.In the case of total power limited,joint optimization algorithm of artificial noise and beamforming with the source node power allocation is obtained.This thesis first analyzes the system model in relay amplify forward way.With secrecy rate expression,the original complex non-convex problem is transformed into convex optimization problem.Then searching the global optimal sending power sets and jointly optimizing the artificial noise covariance and beamforming vector to maximize the worst secondary user secrecy rate based on the semidefinite programming.Finally,the thesis simulate the secrecy rate verse different number of relay,relay total power and interference temperature,and results show that this scheme has good secrecy performance.Aimed at the existing relay secure transport problems with inaccurate channel state information under relay cognitive radio network that eavesdropper with multiple antennas,this thesis expands the existing researches,then designs and optimizes the physical security transmission scheme with imperfect eavesdropping side.Thus,this thesis designes it as secondary user's worst secrecy rate maximization problem when relay works with channel status information error to eavesdropper.In order to achieve the purpose of saving energy and protecting the main users,the maximum transmission power of relay and the interference temperature of primary user will be considered as constraint conditions.Secondly,this thesis gives the closing confidential rate of the network model,and introducing auxiliary variables,by using the method of semi-definite relaxation the original non-convex problem is converted into a series of convex constraints,so the objective function can get local optimal solution in finite iteration.Additionally,through the simulation experiments show that the proposed scheme has good robustness;when the error is small the scheme performance is consistent with accurate channel state information.