Research On Trajectory Optimization And Power Allocation Of UAV Relay System

In recent years,Unmanned Aerial Vehicle(UAV)has been playing an increasingly important role in wireless communications,and the research on UAV as a relay has also attracted wide attention.The deployment of UAVs,especially the trajectory planning and resource allocation,is the key to improve the performance of UAVs relay auxiliary communication system,and is also a very challenging task.Therefore,the trajectory optimization and resource allocation of UAV aided relay communication system are studied in this thesis.The specific research content includes the following three aspectsIn view of the security problems faced by UAV relay system,the threat from aerial eavesdroppers in unknown locations is considered,joint optimizationdesign of UAV trajectory and transmitting power is studied,taking the secrecy rate as the optimization target,An efficient secure based joint trajectory and power optimization(SJTPO)algorithm is proposed in this thesis.At the same time,the optimal trajectory and power distribution scheme are obtained by splitting the optimization problem into four sub-problems and transforming them into convex optimization problems one by one.The simulation results show that compared with other schemes,the proposed SJTPO algorithm can improve the security of the system by at least 10%.Considering the scene of the high communication quality requirements,the relationship between the throughput of UAV relay auxiliary communication system and the trajectory and power is analyzed,aiming to optimization the throughput.The trajectory and transmitting power of UAV are jointly optimized to maximize the throughput of the system.a joint trajectory and power optimization(JTPO)algorithm is proposed.First,the optimization problem is divided into two sub-problems.Secondly,the subproblems are transformed into convex optimization problems respectively.Finally,the trajectory and power distribution scheme of UAV are obtained by solving the two sub-problems alternately.simulation show that the proposed JTPO algorithm improves the throughput of UAV auxiliary communication system by 41%.Considering the limited energy of UAV,the energy efficiency of UAV relay auxiliary communication system is studied in this thesis.In order to improve the energy efficiency of the system,a joint optimization design is carried out for the trajectory and power of the UAV,and an energy-efficiency based joint trajectory and power optimization(EJTPO)algorithm is proposed.Firstly,the problem of variable coupling in energy efficiency optimization is solved.Secondly,the optimization problem is solved iteratively.Finally,the optimal trajectory and power distribution scheme are obtained.Simulation results show that the proposed EJTPO algorithm can effectively improve the energy efficiency of the system.In this thesis,secrecy rate,throughput and energy efficiency are used to measure the performance of UAV relay communication system,and three effective algorithms are proposed to obtain the optimal trajectory and power respectively.Simulation results show that the proposed scheme can effectively improve the performance of UAV relay system.