摘要： 智能反射面（RIS）被认为是未来无线通信技术中具有潜力的技术之一。无人机（UAV）也因其独特优势在无线通信领域日益受到关注。然而，随着通信环境的日益复杂化，信息传输面临着日益严峻的窃听风险，RIS与UAV的结合则为未来的无线通信领域开辟了新的解决路径与可能性。为此提出了一种基于RIS-UAV的保密无线通信系统。该系统利用UAV的灵活性和RIS的动态调整能力，有效抵御潜在窃听行为。从物理层安全角度出发，该系统考虑了RIS的相移和UAV的飞行轨迹，旨在最大化系统的平均保密速率。由于该问题本质上是非凸的，本文的解决方案将问题分解为两个子问题。首先通过系统的特殊结构推导出了相移的闭式解，其次通过一阶泰勒展开将UAV的飞行轨迹转化为凸问题，并采用逐次凸逼近法进行迭代求解。最后仿真结果显示，该系统在平均保密速率方面表现良好，与基准方案相比，该系统的平均保密速率提升了约 ；与固定RIS和无RIS方案相比，性能也提升显著。此外，该方案在安全性、计算复杂度等方面也显示出明显优势，计算复杂度为 。

Abstract: Reconfigurable intelligence surface (RIS) is considered a promising technology for future wireless communication. Unmanned aerial vehicles (UAV) are increasingly gaining attention in the wireless communication field due to their unique advantages. However, with the increasing complexity of communication environments, information transmission faces increasingly severe eavesdropping risks, and the integration of RIS with UAV opens up new solutions and possibilities for the future field of wireless communications. Therefore, a secure wireless communication system based on RIS-UAV is proposed. The system utilizes the flexibility of UAVs and the dynamic adjustment capability of RIS to counter potential eavesdropping behavior effectively. Starting from the physical layer security perspective, the system considers the phase shift of RIS and the flight trajectory of UAV, aiming to maximize the average security rate of the system. Since the problem is inherently non-convex, the solution decomposes the problem into two subproblems. First, the phase shift's closed-form solution has been derived from the system's unique structure. Subsequently, the flight trajectory of the UAV is converted into a convex optimization problem via first-order Taylor expansion, and the iterative convex approximation method is used for the iterative solution. The simulation results indicate that, in comparison with the benchmark scheme, the average secrecy rate of this system has increased by approximately . The performance has also improved significantly compared with the fixed RIS and no RIS schemes. Additionally, this scheme demonstrates distinct advantages in aspects such as security and computational complexity, with a computational complexity of .