智能反射面增强抗干扰与反窃听的安全传输策略

Secure Transmission Strategy with Intelligent Reflecting Surface for Enhancing Anti-Interference and Anti-Eavesdropping

针对无线通信中存在窃听者和干扰者的潜在合作关系问题,本文提出了智能反射面增强抗干扰与反窃听的安全传输策略。该策略考虑信道状态信息完美和非完美两种情况,联合优化基站发射波束成形矢量和智能反射面相移矩阵来实现通信系统保密率最大化。在完美信道状态信息下,提出交替优化算法和罚函数法来求解系统保密率优化问题;在非完美信道状态信息下,利用松弛变量、S-引理、拉格朗日乘子法和交替优化等方法将系统保密率的非凸二次约束二次规划问题转化为确定性凸优化问题并求解。并进一步地分析了基站传输功率、IRS反射单元数量、信道不确定性等参数对系统保密率的影响。数值结果表明,本文所提策略经过3至6次的迭代均能达到收敛。并且与现有的最大比发射策略和随机相移策略相比,本文所提策略能有效提升系统保密率约20%。

To solve the problem of potential cooperation between eavesdroppers and jammers in wireless communications,a secure transmission strategy with an intelligent reflecting surface(IRS)was proposed to enhance anti-interference and anti-eavesdropping.In this strategy,we account for both perfect and imperfect channel state information(CSI).We established an IRS-assisted multiple input single output(MISO)secure communication system model.The system’s secrecy rate is maximized by jointly optimizing the base station’s transmit beamforming and the IRS’s phase shift matrix.More specifically,the alternating optimization algorithm and constructor method were presented to solve the secrecy rate optimization problem of a communication system under perfect CSI,where the difference of the convex functions algorithm and first-order Taylor expansion were used to obtain the constraint function under the rank one constraint,and then the penalty function method was used to bring the penalty term related to the constraint function into the objective function for the solution.To address the non-convex quadratic secrecy rate problem in the communica-tion system,we transformed it into a convex optimization problem.This was achieved using a slack variable,the S procedure,the Lagrange multiplier method,and alternating optimization,particularly under conditions of imperfect CSI.Furthermore,the base station transmission power,the number of IRS reflection units,channel uncertainty,and other parameters of the system security rate were also analyzed.Numerical results show that the system secrecy rate in-creases with the increase in the number of IRS reflection units under perfect channel state information and imperfect channel state information.This is because the number of IRS reflection units increases,the diversity gain and degree of freedom in space will increase,and the safety performance of the system will be enhanced.Moreover,the channel un-certainty will result in a channel estimation error,thus leading to a lower secrecy rate for the system in the worst signal transmission environment.Numerical results also show that the proposed strategy can achieve convergence after three to six iterations.The proposed strategy enhances the communication system’s secrecy rate by approximately 20%compared to the existing maximum ratio transmission strategy and the random phase shift strategy.