基于多IRS辅助的MU-MISO系统安全通信方案

Secure communication scheme of MU-MISOsystem based on multiple IRS assistance

在无线通信系统中,智能反射面(intelligent reflecting surface,IRS)可以调控反射单元的相移来反射信号,用于增强用户信号并抑制窃听者信号,解决基站和用户之间的安全通信问题。针对该问题,以系统加权和保密速率最大化为目标提出一种多IRS辅助多用户多输入单输出(multi user-multiple input single output,MU-MISO)系统的安全通信方案。该方案首先将最大化加权和保密速率问题分解为发射波束形成和人工噪声向量优化、多IRS相位矩阵优化的两个子问题;其次,采用半定松弛、引用文献定理、辅助变量替换、一阶泰勒近似等方法,将每个子问题转换为简单凸问题进行求解;最后,基于交替优化算法依次求解两个凸优化子问题。数值仿真结果表明,与另外三个方案相比,所提方案可以有效增强系统的安全通信性能,并表明了多IRS部署比单个IRS可以实现更好的系统安全性。

In wireless communication system,IRS can regulate the phase shift of reflecting units to reflect signals,which is used to enhance user signals and suppress eavesdropper signals and solve the problem of secure communication between base station and users.To address this issue,this paper proposed a secure communication scheme for multi IRS assisted multi user-multiple input single output system,with the goal of maximizing system weighted sum secrecy rate.This scheme firstly decomposed the problem of maximizing weighted sum security rate into two subproblems:transmission beamforming and artificial noise vector optimization,and multi-IRS phase matrix optimization.And then,this scheme transformed each subproblem into a simple convex subproblem for solution by using methods such as semidefinite relaxation,citation theorems,auxiliary variable substitution,and first-order Taylor approximation.Finally,this paper obtained the maximum weighted sum secrecy rate by sequentially solving two convex optimization subproblems based on the alternating optimization algorithm.The numerical simulation results show that the proposed algorithm scheme can effectively enhance the secure communication performance of the system compared with the other three schemes,and indicate that multiple IRS deployments can achieve better system security than a single IRS.