Multicast hybrid precoding reaches a compromise among hardware complexity, transmission performance and wireless resource efficiency in massive MIMO systems. However, system security is extremely challenging with the appearance of eavesdroppers. Physical layer security (PLS) is a relatively effective approach to improve transmission and security performance for multicast massive MIMO wiretap systems. In this paper, we consider a transmitter with massive antennas transmits the secret signal to many legitimate users with multiple-antenna, while eavesdroppers attempt to eavesdrop the information. A fractional problem aims at maximizing sum secrecy rate is proposed to optimize secure hybrid precoding in multicast massive MIMO wiretap system. Because the proposed optimized model is an intractable non-convex problem, we equivalently transform the original problem into two suboptimal problems to separately optimize the secure analog precoding and secure digital precoding. Secure analog precoding is achieved by applying singular value decomposition (SVD) of secure channel. Then, employing semidefinite program (SDP), secure digital precoding with fixed secure analog precoding is obtained to ensure quality of service (QoS) of legitimate users and limit QoS of eavesdroppers. Complexity of the proposed SVD-SDP algorithm related to the number of transmitting antennas squared is lower compared with that of constant modulus precoding algorithm (CMPA) which is in connection with that number cubed. Simulation results illustrate that SVD-SDP algorithm brings higher sum secrecy rate than those of CMPA and SVD-SVD algorithm.

组播混合预编码在大规模 MIMO 系统中的硬件复杂性、传输性能和无线资源效率之间取得了折衷。然而，随着窃听者的出现，系统安全极具挑战性。物理层安全 (PLS) 是提高组播大规模 MIMO 窃听系统传输和安全性能的一种相对有效的方法。在本文中，我们考虑一个具有大量天线的发射器将秘密信号通过多个天线传输给许多合法用户，而窃听者则试图窃听信息。为了优化多播大规模MIMO窃听系统中的安全混合预编码，提出了一个旨在最大化和保密率的分数问题。因为提出的优化模型是一个棘手的非凸问题，我们等价地将原始问题转化为两个次优问题，分别优化安全模拟预编码和安全数字预编码。安全模拟预编码是通过应用安全信道的奇异值分解 (SVD) 来实现的。然后，采用半定程序（SDP），得到具有固定安全模拟预编码的安全数字预编码，以保证合法用户的服务质量（QoS）和限制窃听者的服务质量。所提出的与发射天线数量平方相关的 SVD-SDP 算法的复杂度低于与该数量立方相关的恒模预编码算法 (CMPA)。仿真结果表明，SVD-SDP算法比CMPA和SVD-SVD算法带来更高的和保密率。