Research On Deployment Of Unmanned Aerial Vehicle Relays

Due to geographical constraints,it is difficult to set up base stations in the ocean and some areas;after the natural disaster,the communication demand in the disaster area increases sharply,and the ground base station is damaged seriously,these cases will lead to the breakdown of the communication system.Unmanned aerial vehicle(UAV),with its unique advantages of space flexibility,convenience,high capacity,and wide coverage,has become a good choice for ground communication supplement.As a relay,UAV participates in the communication task,which can be quickly and flexi-bly deployed to provide communication service for the missing area of base stations.The deployment scheme of UAV directly controls the performance of UAV communi-cation network and determines whether the UAV can complete the communication task.Therefore,this thesis studies the deployment of UAV against the background of UAV relay,based on its static and dynamic characteristics.The main research work of this thesis includes the following two points:Aiming at the static characteristic of UAV,a static 3D deployment scheme of UAV is proposed.Considering that users on the ground have different quality of service(QoS)requirements,UAVs are deployed in three-dimension(3D)space to achieve full coverage of users on the premise of meeting users'different QoS requirements.In order to reduce application cost and improve efficiency,this thesis constructs an optimization problem aiming at minimizing the number of UAVs and proposes a heuristic algorithm to solve it.Firstly,according to the characteristic of the air to ground(ATG)channel of the UAV,the relationship between the coverage and the hovering height of the UAV under different path loss(PL)conditions is deduced.Then,based on the solution,UAVs are deployed by user convex hull(CH)to the inside of the users in a spiral arrangement,to obtain the optimal location of each UAV.Finally,the proposed algorithm is compared with the existing full-coverage deployment algorithm.Simulation results show that the proposed algorithm can effectively reduce the number of required UAVs and has high-performance gains.Aiming at the dynamic characteristic of UAV,a UAV trajectory planning strategy is proposed.When users are moving in real time,they are marching in different direc-tions all the time,in order to keep the communication uninterrupted during the users'movement,the dynamic characteristic of UAV can be used to track the users in real time.In order to ensure the fairness of users,this thesis constructs a trajectory planning prob-lem aiming at maximizing the minimum average rate of users,which is a mixed integer non-linear programming(MINLP)problem with two optimization variables.Firstly,the integer restriction is relaxed.Then,block coordinate descent method(BCDM)was used to solve the problem.When each variable was optimized separately,the subprob-lem was approximated as a convex optimization problem,and CVX toolbox was used to solve each convex optimization subproblem.Finally,the iterative algorithm of tra-jectory planning is designed by using the idea of the alternating direction method of multipliers(ADMM).Simulation results verify the effectiveness of the proposed algo-rithm and show that reasonable trajectory planning can increase system capacity and communication rate of users.Research shows that the UAV deployment strategy proposed in this thesis can make full use of the characteristics of UAV to meet different application requirements in dif-ferent practical scenarios,and improve network performance.