Research On Position Deployment And Trajectory Optimization For UAV Communications

With the rapid development of wireless communication technology,wireless network terminals have shown massive growth,and various new business scenarios have also emerged.The sixthgeneration mobile communication technology not only surpasses the 5G standard in terms of transmission rate,delay,power and other performance,but also extends the communication range to multiple fields such as air,space,ground and sea,which greatly promotes the research and development of UAV communication technology.UAVs are widely used in military and civilian communications and other fields due to their unique advantages such as simple operation,strong mobility and wide adaptability.As an aerial platform equipped with wireless communication equipment,UAVs can not only access the ground communication network and form a multi-UAV self-organizing network,but also integrate with satellite communication so as to improve the communication,perception,load and anti-destruction capabilities of the entire communication network.Therefore,UAV-assisted communications can be used to improve the communication quality between ground terminals and at the same time expand the coverage of the communication network,so as to meet the requirements of ultra-high-speed communication,massive terminal access,and high reliability and low delay of 5G and 6G systems.However,most of the current research related to UAV communication is limited to the simple optimization of communication resources of a single UAV,which lacks practical application feasibility compared with multi-UAV communication scenarios.Therefore,this thesis considers the multi-UAV communication system as the air base station and data relay,and studies the optimization problems of its location deployment,flight trajectory and communication resource allocation.The main research contents are as follows:(1)The three-dimensional deployment of UAV communication nodes and the optimization of power distribution are studied.Firstly,the three-dimensional position deployment,link propagation,physical interference and rate constraints of UAV communication nodes are analyzed,and the communication system model of UAV as a temporary base station covering ground terminal users is constructed.Secondly,an optimization problem with the goal of energy efficiency and coverage is proposed to jointly optimize the three-dimensional space coordinate position of the UAV communication node and its transmit power.Finally,the multi-objective particle swarm optimization is used to solve the problem,and finally the optimal solution is obtained and the local optimum is prevented.The simulation results show that the proposed scheme can not only improve the energy efficiency of the UAV communication network,but also improve the coverage and expand the service range of communication,and at the same time,it can realize the three-dimensional position deployment of UAV communication nodes and the optimal power distribution results.(2)The optimization problem of flight trajectory and resource allocation of UAV relay nodes is studied.Firstly,the interference,link scheduling and rate constraints between UAV nodes in the multiUAV relay communication system are analyzed,and the system model of UAV as a data relay to realize ground user communication is constructed.Secondly,an optimization problem aiming at throughput is proposed to jointly optimize the flight trajectory,node selection and communication resources of UAV relay nodes.Finally,an improved deep deterministic policy gradient algorithm is used to analyze the problem and obtain the optimal solution.The simulation results show that the proposed scheme can not only maximize the throughput of ground terminal users and their links,but also realize the optimization of the UAV’s flight trajectory and the reasonable allocation of communication resources,while reducing the number of algorithm iterations and accelerating the convergence process.