Research On Throughput Optimization Strategy Of UAV-assisted Wireless Communication System

In recent years,electronic technology has developed rapidly.UAVs have the advantages of small size,light weight,strong maneuverability,easy deployment and low maintenance costs,and good line-of-sight links.UAV-assisted wireless communication has also been widely concerned.However,UAV-assisted wireless communication system that UAVs assiste still has many challenges.UAVs,as aerial base stations which assist cellular network to perform traffic offloading,can reduce the traffic load of base stations and improve the Qos of users.However,there is interference between UAVs and ground base stations,which will affect the quality of communication services.Due to the uneven distribution of users,the fairness of users also needs to be studied.Changes in the location of the drone will cause changes in users’ transmission rate.Optimizing the location of the drone to maximize system throughput is challenging.This thesis is aim to obtain the throughput maximization of the UAV-assisted wireless communication system,and to conduct in-depth research on the resource allocation and UAV trajectory optimization in the two scenarios of UAV-assisted cellular network traffic unloading and UAV-assisted data collection.The main contributions are as follows:First of all,this thesis puts forword a system model of a single drone assisted multi-cell cellular traffic offloading,which aims at reducing the influence of traffic overload of the hotspot cells with a surge in traffic.In this system,UAVs are as mobile base stations which supply communication services to users at the edge of cells and assist the cell in offloading traffic.With the aim of satisfying the users’ Qo S,we jointly optimize the user unloading time scheduling and drone trajectory,which is aimed to obtain the throughput maximization of edge users.This thesis provides a successive convex approximation method based on a two-stage alternative optimization algorithm,which splits the target problem into two sub-problems to solve iteratively.The simulation results show that the scheme can achieve interference avoidance between the base station serving users and UAVs serving users availably and guarantee that users can acquire services fairly.Secondly,for the problem of limited spectrum resources,this thesis presents a UAV data collection system model where drones collect data with NOMA,under the circumstance of ensuring the minimum communication service quality of each node,joint optimization of the UAVs’ location,sensor grouping and power control is aimed to obtain the maximization of the sum of uplink transfer rate.For above matter,this thesis presents a hypergraph coloring-power control algorithm,which is solved iteratively by decomposing the target issue.The simulation results show that the throughput of the scheme is better than other schemes.