Attention-based UAV Trajectory Optimization for Wireless Power Transfer-assisted IoT Systems

--Unmanned Aerial V ehicles (UA Vs) in Wireless Power Transfer (WPT)-assisted Internet of Things (IoT) systems face the following challenges: limited resources and suboptimal trajectory planning. Reinforcement learning-based trajectory planning schemes face issues of low search efficiency and learning instability when optimizing large-scale systems. T o address these issues, we present an Attention-based UA V Trajectory Optimization (AUTO) framework based on the graph transformer, which consists of an Attention Trajectory Optimization Model (A TOM) and a Trajectory lEarNing Method based on Actor-critic (TENMA). In A TOM, a graph encoder is used to calculate the self-attention characteristics of all IoTDs, and a trajectory decoder is developed to optimize the number and trajectories of UA Vs. TENMA then trains the A TOM using an improved Actor-Critic method, in which the real reward of the system is applied as the baseline to reduce variances in the critic network. This method is suitable for high-quality and large-scale multi-UA V trajectory planning. Finally, we develop numerous experiments, including a hardware experiment in the field case, to verify the feasibility and efficiency of the AUTO framework. I NTRODUCTION With the advancement of 5G, the Internet of Things (IoT) has become widely used in a variety of fields, including environmental monitoring, healthcare, and industry 4.0, among others. However, due to limited transmitting power and battery capacity, Internet of Things Devices (IoTDs) perform poorly in long-distance communication.