Radio Resource Management And Trajectory Planning For UAV Relaying Systems

With the development of the fifth generation mobile communication technology,as a device which can assist wireless communication,UAV has undertaken operations in many special environments due to its low cost,deployment easily,and good line-ofsight links.UAV has played an active role in various vertical industries and become an important complementary technology for wireless communication because it can provide fast and reliable communication services.UAV relay is mainly used for temporary communication.As an air base station,it provides connection services for ports that cannot directly communicate on the ground,which can effectively improve the communication efficiency,channel capacity and coverage area of wireless networks.In the UAV relay communication system,reasonable planning for the UAV's flight path and wireless resource allocation can maximize the system's transmission capacity and communication performance.According to the real application scenario and flight missions,this paper established a traditional three-node communication model.In order to improve the communication efficiency of the system,a data buffer is equipped on the UAV relay,the data received from the source can be temporarily stored in the buffer before forwarded to the destination on the ground.This paper studied the work of jointly optimizing UAV trajectory and wireless resource allocation to achieve overall system performance improvement under the conditions of UAV mobility and information causality through two different algorithms.The main contents of this paper are as follows:(1)According to the proposed UAV communication system,a joint optimization method for maximizing system throughput is studied based on time slot resource allocation and trajectory planning.However,the optimization problem is a non-convex problem,so it needs to be decomposed into two sub-problems.The trajectory subproblem can be converted into a standard convex form by continuous convex approximation technology and solve the sub-problem of time slot allocation through linear programming.Alternate iteration to get the optimal solution of the original problem.The simulation results show the convergence and high efficiency of algorithm we proposed,which can obtain system capacity gains significantly.(2)In view of the high computational complexity and time-consuming of continuous convex approximation algorithm,in order to reduce the complexity to meet the needs of online planning applications,based on the heuristic algorithm idea,still under the algorithm framework of the cross iteration of two sub-problems,a greedy strategy's low complexity trajectory optimization algorithm replaced the continuous convex approximation in this paper.By analyzing the constraints,the solution space is reduced,and the greedy algorithm is used to select the optimal solution within the limited range,which avoids the approximation and solution process of complex optimization problems,and greatly reduces the algorithm complexity and running time.The simulation results show that compared with the solution using continuous convex approximation algorithm to solve the sub-problem of track optimization,the proposed low complexity heuristic algorithm can achieve a performance close to the original algorithm and significantly reducing the solution time and improving the system's performance effectively.