The Internet of things (IoT) has emerged as a platform for connecting massive physical devices to collect and analyze data for decision-making. Wireless devices in IoT are usually energy-constrained and thus need to be powered by a stable and reliable energy source in order to maintain a long network lifetime. An unmanned aerial vehicle (UAV) as an energy source is a proper and applicable way to supply energy to wireless devices in IoT, due to its flexibility and potential of providing line-of-sight (LOS) links for wireless air-to-ground channels. In this paper, a UAV-aided wireless powered relay communication system is presented, where a UAV firstly emits energy to a source and a relay, and then, the source and relay cooperatively transmit information to their destination. To explore the performance limit of the system, a problem is formulated by jointly optimizing the position of the UAV and time allocation to maximize the achievable information rate of the system. By deriving the explicit expressions of the optimal position of UAV and optimal time fraction, the nonconvex optimization problem is efficiently solved. Simulation results show that our proposed method significantly outperforms the benchmark methods.

中文翻译：

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无人机辅助无线电力中继通信系统的联合位置和时间分配优化

物联网（IoT）已经成为连接大型物理设备以收集和分析数据以进行决策的平台。物联网中的无线设备通常受能源限制，因此需要使用稳定可靠的能源来供电，以维持较长的网络寿命。由于无人驾驶飞机（UAV）的灵活性和为无线空对地提供视线（LOS）链接的潜力，因此它是一种合适且适用的向IoT中的无线设备供应能量的方式渠道。在本文中，提出了一种无人机辅助的无线中继通信系统，其中无人机首先向源和中继发射能量，然后，源和中继协同地将信息传输到目的地。要探索系统的性能极限，通过共同优化无人机的位置和时间分配来最大化系统可达到的信息速率，从而解决了问题。通过推导无人机最优位置和最优时间分数的显式表达式，有效地解决了非凸优化问题。仿真结果表明，我们提出的方法明显优于基准方法。