混合有-无源智能反射面辅助大规模MIMO安全传输

针对存在恶意窃听者的大规模MIMO网络安全传输问题，提出了一种混合有-无源智能反射面辅助的下行安全传输方法。受基站总发射功率、混合有-无源智能反射面功率和反射相位模量约束，讨论了最大化系统总保密速率的优化问题，该问题为多变量耦合的非凸优化。提出了基于逐次凸近似的主动波束成形和反射相位优化算法，首先利用交替优化算法将原始问题转变为两个单变量的子问题，然后采用逐次凸逼近或半定松弛算法分别求解每个子问题的最优主动波束成形和反射相位。仿真结果表明，相比传统的被动智能反射面辅助安全传输方案，提出的方案能够有效利用混合有-无源智能反射面高增益的技术优势，进一步提高级联链路的信道增益，获得更高的保密速率。

Hybrid Active-Passive Intelligent-Reflecting- Surface-Assisted Massive MIMO Secure Transmission

This paper proposes a hybrid active-passive intelligent-reflecting-surface-assisted downlink secure transmission method in cell-free massive MIMO networks in the presence of malicious eavesdroppers. Firstly, subject to the total transmit power of the base station, the power of the hybrid active-passive intelligent reflective surface and the reflective phase modulus, the optimization approach to maximize the secrecy rate of the system is discussed, which is a multivariate coupled non-convex optimization problem in nature. Then, the successive convex approximation-based active beamforming and reflection phase optimization algorithm is proposed. The original problem is firstly transformed into two univariate subproblems with the alternating optimization algorithm. After that, the optimal active beamforming and reflection phase for each subproblem are solved separately with a successive convex approximation or a semi-definite relaxation algorithm. The simulation results show that the proposed scheme can effectively utilize the technical advantages of the high gain of the hybrid active-passive intelligent reflecting surface to further improve the channel gain of the cascaded link and obtain higher secrecy rate, compared with the traditional passive intelligent-reflecting-surface-assisted secure transmission scheme.