We develop a comprehensive framework to characterize and optimize the performance of a unmanned aerial vehicle (UAV)-assisted D2D network, where D2D transmissions underlay cellular transmissions. Different from conventional non-line-of-sight (NLoS) terrestrial transmissions, aerial transmissions are highly likely to experience line-of-sight (LoS). As such, characterizing the performance of mixed aerial-terrestrial networks with accurate fading models is critical to precise network performance characterization and resource optimization. We first characterize closed-form expressions for a variety of performance metrics such as frame decoding error probability (referred to as reliability), outage probability, and ergodic capacity of users. The terrestrial and aerial transmissions may experience either LoS Rician fading or NLoS Nakagami-m fading with a certain probability. Based on the derived expressions, we formulate a hierarchical bi-objective mixed-integer-nonlinear-programming (MINLP) problem to minimize the total transmit power of all users and maximize the aggregate throughput of D2D users subject to quality-of-service (QoS) measures (i.e., reliability and ergodic capacity) of cellular users. We model the proposed problem as a bi-partite one-to-many matching game. To solve this problem, we first obtain the optimal closed-form power allocations for each D2D and cellular user on any possible subchannel, and then incorporate them to devise efficient subchannel and power allocation algorithms. Complexity analysis of the proposed algorithms is presented. Numerical results verify the accuracy of our derived expressions and reveal the significance of aerial relays compared to ground relays in increasing the throughput of D2D pairs especially for distant D2D pairs.

中文翻译：

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无人机辅助 D2D 网络在有限块长度机制中的性能

我们开发了一个综合框架来表征和优化无人驾驶飞行器 (UAV) 辅助 D2D 网络的性能，其中 D2D 传输位于蜂窝传输之下。与传统的非视距 (NLoS) 地面传输不同，空中传输极有可能遇到视距 (LoS)。因此，使用准确的衰落模型表征混合空中-地面网络的性能对于精确的网络性能表征和资源优化至关重要。我们首先表征各种性能指标的封闭形式表达式，例如帧解码错误概率（称为可靠性）、中断概率和用户遍历容量。地面和空中传输可能会以一定的概率经历 LoS Rician 衰落或 NLoS Nakagami-m 衰落。基于导出的表达式，我们制定了分层双目标混合整数非线性规划 (MINLP) 问题，以最小化所有用户的总发射功率并最大化受服务质量 (QoS) 影响的 D2D 用户的总吞吐量) 蜂窝用户的度量（即可靠性和遍历容量）。我们将提出的问题建模为双向一对多匹配游戏。为了解决这个问题，我们首先在任何可能的子信道上为每个 D2D 和蜂窝用户获得最佳的封闭形式的功率分配，然后将它们结合起来设计有效的子信道和功率分配算法。提出了所提出算法的复杂性分析。