A Research On Trajectory Planning And Resource Allocation In UAV-based Wireless Powered Communication Network

With the development of large-scale Internet of Things applications,the previous communication technology can no longer meet the requirements of communication,energy transmission and cost of system equipment.Wireless powered communication network(WPCN)and backscatter communication system(BCS)technologies,as new technical theories in recent years,combine traditional wireless energy transmission and wireless information transmission to solve the above problem.In addition,because unmanned aerial vehicle(UAV)can be deployed flexibly and at low cost,it can also obtain a more reliable line-of-sight(LoS)transmission channel through its mobile characteristics,thus UAV-assisted wireless communication also aroused the research interest of scholars.In this context,this thesis studies trajectory planning and resource allocation schemes in UAV-based wireless powered communication network,which mainly includes the following:The thesis proposes a secure backscatter communication system in which an UAV operates both as a source of radio frequency(RF)signals and an information collector.Batteryless backscatter devices(BDs)exploit RF signals emitted by the UAV to upload their own information to the UAV with the existence of multiple eavesdroppers(EDs).Uplink fair-secrecy-rate of BDs is maximised by jointly designing the UAV’s trajectory,the BDs’ scheduling indicators and their backscattering coefficients,while meeting the energy harvesting requirements of batteryless BDs and various flight constraints of the UAV.A low complexity algorithm is developed for solving the non-convex optimisation problem.The simulation results show that the UAV-assisted secure backscatter communication network proposed in this thesis can significantly improve performance compared with other benchmark scheme designs,and also can ensure the security of information communication.The thesis proposes a multi-function communication system based on UAV.UAV uses its flexible characteristics as a signal source to provide carrier signals for ground devices.The system integrates the advantages of BCS and WPCN to achieve the requirement of multi-functional communication.At the same time,two channel models of LoS channel under fixed height and LoS/NLoS channel under variable height are considered separately.Through the joint design of the UAV’s flight trajectory and system time slot resources,the fair rate of the ground devices is maximized,and the system also considers the flight restrictions of the UAV at the same time.The thesis divides the original problem into some sub-problems based on the block coordinate descent algorithm and processes them separately,and finally obtains an approximate solution through joint iterative solution.The simulation results verify the effectiveness of the system.