基于用户协作干扰的IRS辅助安全传输方案

IRS-assisted security transmission scheme based on user cooperative interference

针对协作通信网络无线信道高度开放的信息安全问题,提出一种基于智能反射面(IRS)辅助通信与用户协作干扰的下行链路物理层安全传输方案,并给出了一种基于交替迭代的保密容量最大化算法.该方案中智能反射面通过调整反射相位辅助合法用户进行通信,并且全双工用户在接收有用信号的同时发射人工噪声,从而增强系统信息安全传输.为了求解系统保密容量的非凸优化问题,利用交替迭代算法将其分解为3个子问题,分别对基站波束成形矢量、系统功率分配系数及IRS相移矩阵进行优化.在求解的过程中推导了波束成形矢量和功率分配系数的闭式解,并分别利用连续凸近似和黎曼流形优化两种算法得到了IRS的最佳相移矩阵.分析与仿真结果表明:所提出的方案能够快速收敛,且基于黎曼流形的优化算法具有更低的复杂度.与随机相位或固定功率系数的方案相比,该方案能够显著提高系统安全性能.

For the information security issue of highly open wireless channels in cooperative communication networks,a downlink physical-layer security transmission scheme based on IRS-assisted communication and user cooperative interference was proposed,and an algorithm for maximizing security capacity based on alternative iteration was given. In this scheme, phase shifts of IRS were adjusted to assist confidential communication for legitimate user,and full-duplex user was assigned to send the artificial noise while receiving useful signals to enhance information security of the system. The optimization problem of maximizing system secrecy capacity is non-convex and thus is decomposed into three subproblems in an alternative manner. To be specific, the beamforming vectors at the base station, and the power allocation coefficient of the system and the phase shift matrix at the IRS were optimized alternatively. In the process of optimization, the closed-form expression of the beamforming vectors and power allocation coefficient were derived, while successive convex approximation(SCA) and Riemannian manifold(RM) optimization algorithms were adopted to obtain the optimal phase shifts of the IRS. Analysis and simulation results show that the alternative iteration can converge quickly and the optimization algorithm based on RM has lower complexity than that based on SCA.Furthermore, compared with benchmarks of random phase and fixed power coefficient, the proposed scheme can significantly improve the system security performance.