Unmanned aerial vehicles (UAVs) as aerial relays are practically appealing for assisting Internet of Things (IoT) network. In this work, we aim to utilize the UAV swarm to assist the secure communication between the micro base station (MBS) equipped with the planar array antenna (PAA) and the IoT terminal devices by collaborative beamforming (CB), so as to counteract the effects of collusive eavesdropping attacks in time-domain. Specifically, we formulate a UAV swarm-enabled secure relay multi-objective optimization problem (US2RMOP) for simultaneously maximizing the achievable sum rate of associated IoT terminal devices, minimizing the achievable sum rate of the eavesdropper and minimizing the energy consumption of UAV swarm, by jointly optimizing the excitation current weights of both MBS and UAV swarm, the selection of the UAV receiver, the position of UAVs and user association order of IoT terminal devices. Furthermore, the formulated US2RMOP is proved to be a non-convex, NP-hard and large-scale optimization problem. Therefore, we propose an improved multi-objective grasshopper algorithm (IMOGOA) with some specific designs to address the problem. Simulation results exhibit the effectiveness of the proposed UAV swarm-enabled collaborative secure relay strategy and demonstrate the superiority of IMOGOA.

翻译：摘要：无人机作为空中中继在辅助物联网网络方面具有实际应用价值。本研究旨在利用无人机群通过协同波束赋形技术，辅助配备平面阵列天线的微基站与物联网终端设备进行安全通信，以抵御时域中的合谋窃听攻击。具体而言，我们构建了一个无人机群使能的安全中继多目标优化问题（US2RMOP），通过联合优化微基站与无人机群的激励电流权重、无人机接收机选择、无人机位置以及物联网终端设备的用户关联顺序，以同时最大化关联物联网终端设备的可达和速率、最小化窃听者的可达和速率以及最小化无人机群的能耗。此外，所提出的US2RMOP被证明是一个非凸、NP难且大规模优化问题。为此，我们设计了一种改进的多目标蝗虫算法（IMOGOA）并辅以特定策略来解决该问题。仿真结果验证了所提无人机群协同安全中继策略的有效性，并展示了IMOGOA的优越性能。