# Resource Allocation in Unmanned Aerial Vehicle (UAV)-Assisted Wireless-Powered Internet of Things
## 1 Introduction  
The Internet of Things (IoT) [1; 2; 3; 4] is playing an important and significant role in the next generation mobile communication and wireless networks and is currently used in various services in our daily life. With the implementation of the Internet of Everything, data transmission has become denser, and the amount of information exchange is becoming larger and larger. Therefore, it is essential to use new communication technologies with a greater bandwidth, higher speed, lower latency, and lower energy consumption, to guarantee the popularity of the IoT [5; 6]. Meanwhile, due to the limited energy of the wireless devices in the IoT, the developments and applications of IoT technologies are facing unprecedented and severe challenges. How to provide sustainable energy for the wireless devices in IoT has become an urgent problem to be solved, restricting the development of IoT. As an important method for sustainable energy supply, wireless power transfer (WPT) technology is regarded as an ideal solution for providing sustainable energy to the wireless devices in the IoT and can effectively solve the bottleneck of the limited energy problem in IoT [7; 8]. More and more wireless devices may use WPT technology to reduce the excessive dependence on the battery. WPT has been widely used in portable electronic devices, implanted medical devices, smart homes, electric vehicles (EVs), and so on [9]. Applying the WPT to wireless communication networks can permit wireless powered communication networks (WPCN) to be constructed and can effectively improve the energy efficiency of the network [10; 11; 12; 13; 14; 15; 16; 17; 18; 19]. Compared with the conventional WPT system with a relatively fixed energy source, UAV can dynamically move the IoT devices around, power the IoT devices, and realize the data gathering and transmitting services [20]. The UAV-assisted WPT can greatly improve the performance of the WPCN by dynamically adjusting the power source position. Utilizing the highmobility of UAV, the WPCN can provide ubiquitous energy for wireless devices with a large area distribution, which is faster, more flexible, and more controllable. In this paper, we research the UAV-assisted wireless-powered IoT and solve the resource allocation problem in the proposed IoT system. The resource allocation problem between the UAV and wireless nodes is researched based on a dynamic game and dynamic programming. In our proposed system, the wireless nodes harvest energy from the UAV and transmit data to the UAV. The UAV works as a power source that can move around to charge the wireless nodes based on the wireless power transfer technique. The UAV can also gather all the data from the wireless nodes. A dynamic game-based model for the resource allocation problem between the UAV and wireless nodes is given, and Nash equilibriums for the model can be obtained based on Bellman dynamic programming. Based on the Nash equilibriums, the UAV can optimally allocate its energy resources for wireless power transfer. The main innovations and contributions are summarized as follows:  
* Firstly, the UAV-assisted wireless-powered IoT system is given, including one UAV and many wireless nodes. The UAV tries to harvest the wireless nodes based on the wireless energy transfer techniques. The wireless nodes use the harvested energy for information transmission;
* Secondly, the wireless nodes are divided into two categories based on their energy consumption. The wireless nodes with different energy consumptions will have different energy supplied from the UAV. The energy transferred from the UAV should be different based on the energy consumption;
* The resource allocation problem between the UAV and wireless nodes is formulated as a dynamic game.