Due to the coverage constraint of a wireless base station, mobile users suffer from the unstable network connection and poor service quality, especially for the prevalent video services. As an alternative solution, an unmanned aerial vehicle (UAV) is able to reach the cell edge and serve ground users (GUs). In this paper, we extend the UAV applications to the more challenging adaptive streaming service over fading channel. First, we decompose the system into different modules, and present mathematical models for each of them, including a trajectory model of the UAV, fading channels between the UAV and GUs, and video streaming utility. Second, we formulate the problem as a non-convex optimization problem by optimizing the UAV trajectory and transmit power allocation, jointly with transmission schedule and rate allocation for multiple users. The objective is to maximize the overall utility while guaranteeing the fairness among multiple users under the UAV energy budget and rate-outage probability constraints. Third, to tackle this problem, we first analyze the relationship between transmission rate and rate-outage probability over the fading channel, and then divide the original problem into three subproblems, which can be solved by leveraging the successive convex approximation technique. Furthermore, an overall iterative algorithm over the three subproblems is proposed to obtain a locally optimal solution by applying the block coordinate descent technique. Finally, through extensive experiments, we demonstrate that the proposed design can achieve almost $\text{30}\%$ performance gain in terms of max–min streaming utility for all users, compared with other benchmark schemes.

中文翻译：

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无人机系统辅助自适应视频流：联合优化方法

由于无线基站覆盖范围的限制，移动用户受到网络连接不稳定和服务质量差的困扰，特别是对于流行的视频业务。作为替代解决方案，无人机 (UAV) 能够到达小区边缘并为地面用户 (GU) 提供服务。在本文中，我们将无人机应用扩展到更具挑战性的衰落信道自适应流媒体服务。首先，我们将系统分解为不同的模块，并为每个模块提供数学模型，包括无人机的轨迹模型、无人机和 GU 之间的衰落通道以及视频流实用程序。其次，我们通过优化无人机轨迹和发射功率分配，结合多用户的传输调度和速率分配，将问题表述为非凸优化问题。目标是在无人机能量预算和速率中断概率约束下保证多个用户之间的公平性的同时最大化整体效用。第三，为了解决这个问题，我们首先分析了衰落信道上传输速率和速率中断概率之间的关系，然后将原始问题分解为三个子问题，可以利用逐次凸逼近技术解决这些子问题。此外，提出了对三个子问题的整体迭代算法，以通过应用块坐标下降技术获得局部最优解。最后，通过大量实验，我们证明与其他基准方案相比，所提出的设计可以在所有用户的最大-最小流效用方面实现几乎 $\text{30}\%$ 的性能提升。