This paper develops a framework for analyzing UAV-enabled short-packet communication, leveraging fluid antenna system (FAS)-assisted relaying networks. Operating in the short-packet regime and focusing on challenging urban environments, we derive novel, closed-form expressions for the block error rate (BLER). This is achieved by modeling the spatially correlated Nakagami-$m$ fading link via a tractable eigenvalue-based approach. A high-signal-to-noise ratio (SNR) asymptotic analysis is also presented, revealing the system's fundamental diversity order. Building on this analysis, we formulate a novel energy efficiency (EE) maximization problem that, unlike idealized models, uniquely incorporates the non-trivial time and energy overheads of FAS port selection. An efficient hierarchical algorithm is proposed to jointly optimize key system parameters. Numerical results validate our analysis, demonstrating that while FAS provides substantial power gains, the operational overhead creates a critical trade-off. This trade-off dictates an optimal number of FAS ports and a non-trivial optimal UAV deployment altitude, governed by the balance between blockage and path loss. This work provides key insights for FAS-aided UAV communications.

翻译：本文构建了一个分析无人机短包通信的框架，该框架利用了流体天线系统辅助的中继网络。在短包通信机制下运行，并聚焦于具有挑战性的城市环境，我们推导出了新颖的、闭式的块错误率表达式。这是通过一种易于处理的基于特征值的方法，对空间相关的Nakagami-$m$衰落链路进行建模而实现的。同时，本文还提出了高信噪比渐近分析，揭示了系统的基本分集阶数。基于此分析，我们构建了一个新颖的能效最大化问题，与理想化模型不同，该问题独特地包含了FAS端口选择所带来的不可忽视的时间和能量开销。我们提出了一种高效的分层算法来联合优化关键系统参数。数值结果验证了我们的分析，表明虽然FAS能提供显著的功率增益，但其操作开销带来了一个关键的权衡。这一权衡决定了FAS端口的最优数量以及一个非平凡的最优无人机部署高度，该高度由遮挡和路径损耗之间的平衡所决定。这项工作为FAS辅助的无人机通信提供了关键见解。