In this paper, we propose a secure short-packet communication (SPC) system involving an unmanned aerial vehicle (UAV)-aided relay in the presence of a terrestrial passive eavesdropper. The considered system, which is applicable to various next-generation Internet-of-Things (IoT) networks, exploits a UAV as a mobile relay, facilitating the reliable and secure exchange of intermittent short packets between a pair of remote IoT devices with strict latency. Our objective is to improve the overall secrecy throughput performance of the system by carefully designing key parameters such as the coding blocklengths and the UAV trajectory. However, this inherently poses a challenging optimization problem that is difficult to solve optimally. To address the issue, we propose a low-complexity algorithm inspired by the block successive convex approximation approach, where we divide the original problem into two subproblems and solve them alternately until convergence. Numerical results demonstrate that the proposed design achieves significant performance improvements relative to other benchmarks, and offer valuable insights into determining appropriate coding blocklengths and UAV trajectory.

翻译：本文提出了一种安全短包通信系统，该系统在存在地面被动窃听者的情况下，采用无人机辅助中继。所考虑的系统适用于多种下一代物联网网络，利用无人机作为移动中继，促进一对远程物联网设备间具有严格时延要求的间歇性短包可靠安全交换。我们的目标是通过精心设计编码分组长度和无人机轨迹等关键参数来提升系统的整体保密吞吐量性能。然而，这本质上构成一个难以最优求解的挑战性优化问题。为解决该问题，我们提出了一种基于块连续凸逼近方法的低复杂度算法，将原始问题分解为两个子问题并交替求解直至收敛。数值结果表明，所提设计相比其他基准方案实现了显著的性能提升，并为确定合适的编码分组长度和无人机轨迹提供了重要见解。