Research And Design Of Resource Allocation Scheme For Intelligent Reflecting Surface Assisted Cognitive Radio System

In the past few decades,most of the available spectrum has been used for high-speed communication services.This has led to the scarcity of spectrum resources in wireless communication systems.On the other hand,the utilization rate of a large amount of available spectrum is not high.In order to improve the spectrum utilization of communication systems,the academic community has proposed cognitive radio(CR)technology based on sharing.CR allows SUs and PUs to share spectral resources,which is crucial for improving the spectral efficiency of wireless communication networks.However,currently,CR based communication networks have drawbacks such as low perceptual performance under low signal-to-noise ratio and limited performance improvement under harsh interference conditions.Recently,Intelligent Reflecting Surface(IRS)has been widely used in various fields of wireless communication,and IRS can intelligently regulate the wireless transmission environment.Therefore,deploying IRS in CR can meet the requirements of spectrum efficiency and secure communication.In order to further improve CR perception performance,spectrum efficiency,and communication security,this thesis conducts research on the following contents:(1)A novel IRS assisted perception enhanced spectrum sharing CR network was proposed.In response to this network,an SU and rate maximization optimization problem was established,which jointly optimized the sub base station beamforming vector,intelligent reflector phase shift matrix,and perception time.Due to variable coupling,the constructed optimization problem is non convex.An iterative algorithm based on Block Coordinate Descent(BCD)is proposed to alternately optimize beamforming,intelligent reflector phase,and perception time.Solve non convex objectives and constraint functions using Successive Convex Approximation(SCA),and solve rank one conditional constraints using Semidefinite Relaxation(SDR).Use one-dimensional search to find the optimal perception time.The simulation results demonstrate that the proposed method can quickly converge and significantly improve the perceptual performance and spectral efficiency of the CR network.(2)A security enhanced resource allocation scheme for an IRS assisted perception enhanced CR system is proposed,which further considers the design of covert communication security and network communication security based on the IRS assisted perception enhanced spectrum sharing CR system resource allocation scheme.For the situation where the perception result is spectrum occupancy,due to the spectrum sharing characteristics of CR networks,the interference caused by secondary base stations to the primary user is difficult to avoid.Therefore,this article considers treating this interference as artificial noise to replace the artificial noise emitted by friendly jammers in traditional covert communication,in order to achieve covert communication for the primary user.For this scheme,the minimum error probability of eavesdroppers was first analyzed,and based on this,the concealment constraints of the system were determined.A sub user and rate maximization optimization problem for the system was established considering hidden constraints,and the beamforming vector of the sub base station and the IRS phase shift matrix were iteratively optimized alternately.The simulation results show that the proposed method can converge quickly and greatly improve the Spectral efficiency of cognitive radio network and the concealment performance of the main network.