Wireless Secure Communication System Based On IRS Assistance

Intelligent reflecting surface(IRS)can reflect signals by adjusting the phase shift of the reflecting element to enhance expected signals or suppress unexpected signals,and has broad application prospects in the field of secure communication.This thesis studies a secure communication system assisted by IRS and establishes an optimization problem for maximizing the confidentiality rate in the IRS assisted secure communication system.The optimization problem is mainly decoupled into two subproblems through alternating optimization,and then the beamforming matrix at the transmitter and the reflection phase shift matrix of IRS are designed separately to maximize the confidentiality rate of legitimate communicators.The main research content and innovation points of this article are as follows:(1)For multiple-input multiple-output(MIMO)secure communication systems assisted by multiple IRSs,an optimization problem for maximizing the confidentiality rate in multiple IRSs assisted secure communication systems was established.Based on the generalized Rayleigh quotient,an improved alternating optimization algorithm was proposed to normalize the obtained optimal solution when optimizing the reflection phase shift matrix of IRS,ensuring that it meets the constraints,then it is substituted into the alternating optimization for cycling.The simulation results show that when the number of IRS reflective components is large,the performance of this algorithm is significantly better than existing algorithms.(2)We studied a MIMO secure communication system with IRS assisted by artificial noise and established an optimization problem related to system confidentiality.We used an alternating optimization algorithm based on successive convex approximation(SCA)to solve this non-convex problem.After simulation verification,additional artificial noise can increase the overall performance of the system by generating interference at the eavesdropping end.(3)We studied the robustness design scheme of IRS assisted multi-user secure communication system in the presence of hardware impairments at the transmitter and receiver.We have established an optimization problem for the maximum confidentiality rate of multiple users,using an alternating optimization algorithm based on SCA to solve the beamforming vector of the base station and the phase shift matrix of the IRS.The simulation results show that the proposed design scheme is superior to the one that ignores the impact of hardware impairments.