Research And Simulation Of Trajectory Planning For UAV Assisted Communication Network

With the continuous development and the increasing popularity of unmanned aerial vehicle(UAV)technology,UAV has been more and more widely used.Due to their prominent features of high mobility and flexible deployment,the use of UAVs as aerial base stations to assist communication for the future wireless system has a high practical value.UAV trajectory planning is a key problem in related areas,especially in the case of UAV-assisted communications,where proper trajectory planning can significantly reduce communication distances,which is critical to improving mission execution efficiency and system communication quality.In the existing research on the optimization of UAV trajectory,most communication networks are in time division multiple access mode and the user size is small.Based on the above background,this thesis pays attention to the design of the trajectory planning scheme of the UAV-assisted communication network to solve the trade-off of system performance and task completion time.Through the MATLAB platform,the effect of the proposed algorithm is simulated.The work is divided into the following sections:First of all,this thesis studies the problem of UAV trajectory planning in the downlink air-to-ground wireless network based on non-orthogonal multiple access technology(NOMA)technology,where a single UAV is deployed as an aerial base station to provide periodic service for a group of ground users.In order to maximize the system sum rate in a limited time,an iterative algorithm for jointly optimizing user scheduling and UAV trajectory is proposed.In order to find the optimal users to communicate with.we present a method of user partitioning based on k-Means clustering algorithm and a strategy for selecting subset to schedule on the basis of NOMA technology.The simulation results are provided to show the feasibility of the optimal UAV trajectories with different objective functions,and to indicate that the NOMA-based UAV system provides the benefits of achieving a better air-ground communication compared to the benchmark schemes.Secondly,this thesis studies the trajectory planning of multi-UAV air-to-ground wireless network based on NOMA technology.First,the user partition is realized by two-step clustering algorithm,and then two kinds of UAV access sequence strategies are implemented,namely,the predetermined selection order based on the ant colony algorithm and the adaptive selection order of online planning to better respond to the users’ needs.In addition,the power control and UAV trajectory planning are jointly optimized to achieve higher system sum rate.The simulation results under different schemes are provided to verify the effectiveness of UAV access sequence strategies and to show the feasibility of the proposed UAV cooperative trajectory planning algorithm.Finally,this thesis studies the problem of multi-UAV cooperative trajectory planning in three-dimensional(3D)space.First,the modeling process of 3D planning space is analyzed,a framework for serving UAV users is given,and then the flight space pre-processing method based on the Tyson polygon is proposed,and the corresponding trajectory planning is carried out through iterative optimization.Finally,the simulation results under the number of different UAV base stations are compared,which shows the convergence performance of the system framework.The above work can provide theoretical and practical references for the trajectory planning problem in the UAV-assisted wireless network,and our results are also helpful for new application scenarios for NOMA in the future communication system.