Research On Resource Optimization Of Wireless Security Communication Aided By Intelligent Reflecting Surface

In recent years,the field of wireless communication has a higher requirement for physical layer secure communication.However,traditional communication technology has some problems,such as high complexity algorithm,energy consumption and high hardware costs.Thus,recently,Intelligent Reflecting Surface(IRS)has been proposed and applied to wireless communication systems.IRS is a passive two-dimensional reflecting surface,and the reflecting phase of the reflecting unit on the IRS can be modified by software.By designing the reflecting phase of IRS,the received signals of legitimate users can be superimposed and the signals of eavesdropping users can be cancelled at the same time.The compatibility of IRS makes it possible to combine with traditional secure communication technologies such as multiple antennas and artificial noise,so it is very important to introduce IRS into the research of secure communication in physical layer.In this paper,the IRS is applied to the traditional physical layer secure communication system,and the corresponding resource optimization strategy is proposed for the ground base station and the UAV base station.Firstly,the multi-input Single Output(MISO)system of a ground base station with multiple eavesdropping users is considered to optimize the beamforming and artificial noise vectors of the base station and the reflection phase of the IRS.In this paper,we propose an alternate iterative optimization algorithm based on Semi-positive definite relaxation(SDR)and minimax theorem.Simulation results show that the proposed algorithm can effectively reduce the power consumption of the system,and prove that IRS can be combined with artificial noise to further improve system performance.Second,consider the UAV base station's single eavesdropping user's single legitimate user's Multi-Input Multi-Output(MIMO)system.By optimizing the position of the UAV,the transmitting beamforming of the UAV,the artificial noise vector and the reflection phase of the IRS,the problem of maximizing the system safety rate is studied.In this paper,we propose an alternating iterative algorithm based on block descent(BCD),Complex Circle Manifold(CCM),and Genetic Algorithm(GA)for the mathematical problem of multivariable coupling.Simulation results show that the algorithm can effectively improve the system security rate,and verify the IRS in the UAV communication system under the MIMO system has a certain role in improving the security rate.