Research On Energy Saving Of UAV Platform In Air To Ground Communication System

Unmanned Aerial Vehicle(UAV)has been widely used in wireless communication with the advantages of high mobility,low cost and line of sight communication.In the UAV-enabled Air-to-Ground(A2G)networks,the three dimensional(3D)free movement and limited onboad energy of UAV lead to rapid change of the network topology.The frenquent information exchange among UAVs introduces more energy consumption for the communaction module and fight module.How to improve system energy efficiency and reduce terminal energy consumption become two major challenges for UAV-enabled A2G communication system.This thesis aims to study energy saving of UAV base station(BS)and mobile terminal in UAV network.The main contents are as follows:(1)Performance analysis of user data rate and system energy efficiency in A2G communication system:Aiming at the communication scenario of UAV acting as an aerial BS,considering the impact of UAV jitter caused by airflow and wireless environment on establishment of robust A2G link,models for the vibrations of UAV platform in both horizontal azimuth and vertical elevation are proposed.Based on which,distortion and shift of the beam-illumination area are analyzed.Further,beam-illumination probability of a randomly located ground receiver is derived.Tractable framework for analyzing the user data rate and system energy efficiency is developed.Simulation results show that UAV height,beamwidth and jitter angle are the main factors affecting the user data rate and system energy efficiency.The optimal beamwidth exists under the impact of UAV jitter.In the scenario with fixed UAV height and beamwidth,the system energy efficiency with jitter angle 8π/180 is reduced by 15.3%compared with that with jitter angle 4π/180.(2)Joint optimization of beamwidth and transmission power of UAV for energy efficiency:Considering the impact of UAV jitter on beam coverage and data rate in the communication scenario of UAV acting as an aerial BS,the energy efficiency optimization model under the rate constraint of edge users is established.The joint iterative method is introduced to optimize the beamwidth at fixed transmit power and the transmit power at fixed transmit power,respectively.Variable substitution and difference-of-concave algorithm are applied to transform the non convex optimization problem into convex optimization problem.Further,a joint optimization design scheme of UAV beamwidth and transmission power is proposed.Simulation results show that compared with the scenario with jitter angle 4π/180,the system energy efficiency with jitter angle 8π/180 is reduced by 21.3%.The energy efficiency of the proposed algorithm with fixed UAV height and jitter angle can achieve 6.6 times improvement compared with only optimizing beamwidth and 4.4 times improvement compared with only optimizing transmission power.(3)Energy saving of mobile terminal based on Radio Resource Management(RRM)measurement in UAV network:Aiming at the energy saving of mobile terminal in UAV network,considering the impact of terminal location and moving speed on RRM measurement power consumption,a clustering based energy saving scheme for relaxation measurement is proposed.It can reduce the number of cells measured by the terminal in the clustering.Another energy saving scheme for relaxing measurement cycle is proposed.The proposed cycle backtracking mechanism enables the terminal to adaptively adjust the measurement interval in the idle period and reduce power consumption in whole measurement cycle.Analysis results show that the proposed two measurement schemes can reduce the measurement power consumption without impacting terminal mobility,and realize the effective energy saving of terminal.Aiming at the energy saving of UAV BS in A2G communication system,tractable framework for analyzing the user data rate and system energy efficiency under the impact of UAV jitter is developed.A joint optimization scheme of beamwidth and transmission power to maximize system energy efficiency is also proposed.Aiming at the energy saving of mobile terminal in UAV network,two energy saving schemes for RRM relaxation measurement are proposed.The study in this thesis provides theoretical guidance for energy saving of UAV communication platform in air-ground integrated network.