An unmanned aerial vehicle (UAV)-aided secure communication system is conceived and investigated, where the UAV transmits legitimate information to a ground user in the presence of an eavesdropper (Eve). To guarantee the security, the UAV employs a power splitting approach, where its transmit power can be divided into two parts for transmitting confidential messages and artificial noise (AN), respectively. We aim to maximize the average secrecy rate by jointly optimizing the UAV's trajectory, the transmit power levels and the corresponding power splitting ratios allocated to different time slots during the whole flight time, subject to both the maximum UAV speed constraint, the total mobility energy constraint, the total transmit power constraint, and other related constraints. To efficiently tackle this non-convex optimization problem, we propose an iterative algorithm by blending the benefits of the block coordinate descent (BCD) method, the concave-convex procedure (CCCP) and the alternating direction method of multipliers (ADMM). Specially, we show that the proposed algorithm exhibits very low computational complexity and each of its updating steps can be formulated in a nearly closed form. Our simulation results validate the efficiency of the proposed algorithm.

中文翻译：

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用于具有功率分配的 UAV 安全通信的低复杂度联合功率分配和轨迹设计

设想并研究了无人机 (UAV) 辅助的安全通信系统，其中无人机在窃听者 (Eve) 存在的情况下向地面用户传输合法信息。为保证安全，无人机采用功率分流方式，其发射功率可分为两部分，分别用于传输机密信息和人工噪声（AN）。我们的目标是通过联合优化无人机的轨迹、发射功率水平以及在整个飞行时间内分配给不同时隙的相应功率分配比来最大化平均保密率，同时受到无人机最大速度约束和总移动能量约束、总发射功率约束和其他相关约束。为了有效地解决这个非凸优化问题，我们通过混合块坐标下降 (BCD) 方法、凹凸过程 (CCCP) 和乘法器交替方向法 (ADMM) 的优点提出了一种迭代算法。特别地，我们表明所提出的算法表现出非常低的计算复杂度，并且其每个更新步骤都可以以近乎封闭的形式制定。我们的仿真结果验证了所提出算法的有效性。