Joint UAV Substitution Trajectory Optimization And Transmit Power Control Design For UAV Relaying Systems

With the development of 5G communication,UAVs can be applied in the field of communication as auxiliary communication devices.In some special scenarios,such as storms,earthquakes,and other disasters,the local basic communication facilities are damaged.UAVs can use their advantages,such as flexible deployment,low power consumption,and strong mobility,to help the disaster areas establish communication links and restore communication.The limited endurance and airborne capability of a UAV may lead to insufficient communication duration and coverage in a UAV-enabled communication system.How to make up for the shortcoming of a UAV’s endurance and to extend the communication duration of a UAV relaying communication system is the research goal of this thesis.Transmit power level and mobility of UAVs are important resources for UAVs to balance communication links.In this thesis,combined with the transmit power control and trajectory optimization algorithm of UAV relays,and combined with the practical scenario as the background,UAV relay substitution schemes have been proposed.The research details of this thesis include the following aspects:(1)The UAV relay substitution schemes have been proposed,which are called heuristic UAV substitution(HUS)scheme and spectral efficient UAV substitution(SEUS)strategy.This thesis studies the single-user relay communication problem under these two relay substitution schemes.The goal is to maximize the end-to-end throughput through the power control on the source and the UAV relays and the optimization of the UAV relays’ trajectories.Since the considered problem is non-convex,we divide the optimization problem into two subproblems and use the optimization techniques of alternating maximization and successive optimization to obtain approximate solutions of them iteratively until convergence.Simulation results show that the proposed SEUS scheme is superior to the HUS scheme and other benchmark schemes in terms of end-to-end throughput.(2)The power and trajectory optimization for UAV relay substitution in a multi-user UAV relaying communication system is studied.This thesis studies how to use joint power control and trajectory optimization to improve the throughput performance of the system under the SEUS and HUS schemes.The goal is to maximize the minimum average rate of the users.The successive alternating optimization and block coordinate descent methods are used to solve the non-convex original problem,and the approximate solution of the original problem has been obtained.The simulation results show that the multi-user relay communication network based on the SEUS scheme has higher user minimum average rate performance than that based on the other benchmark schemes.