Research On Uav Relay Network Echnology Based On Urban Enviornment

With the rapid development of the fifth generation of mobile communications,the mobile terminal business and data flow are increasing exponentially.The massive data makes the traditional ground network face huge bearing pressure.However,ground base stations have problems such as high construction costs,inflexible expansion,and inability to cover disaster-stricken or remote areas.UAV-aided communication has the advantages of mobile deployment and rapid configuration,so becomes one of the effective and feasible solutions to solve the above problems.However,when the UAV-aided communication is applied in the urban environment,the complex building facilities lead to the blocking of wireless signal transmission and the serious path loss of the air-ground channel.In order to make UAV-aided communication give full play to its advantages in urban environment,this paper studies the optimization of UAV relay network based on urban radio map,considers two communication scenarios of UAV static relay and dynamic relay,builds appropriate models for these two types of scenarios,proposes UAV location deployment,path planning and network resource allocation optimization algorithms,and carries out corresponding simulation verification and analysis.The main research and innovation work of this paper are as follows:First,aiming at the problem that building occlusion affects the quality of wireless signal transmission in urban environments,this paper proposes a location deployment and resource allocation strategy for UAV static relays in emergency communication scenarios.It aims to improve the system throughput by balancing the line-of-sight probability and transmission distance on the premise of ensuring the fairness of the system.First of all,based on the urban line-of-sight probability model obtained through simulation and data regression,this study establishes a system model for a single UAV with multi-user relay scenario.Under the constraint of the backhaul link,the joint optimization problem of 3D relay deployment position and power distribution of UAVs is considered.Due to NP-hard,the original problem is decoupled and transformed into a position optimization sub-problem that can be solved using continuous convex approximation techniques and a power optimization sub-problem,and then the block coordinate descent method is used to iteratively obtain a global suboptimal solution.The simulation results prove the effectiveness of the proposed algorithm in the urban environment,and it is verified through experiments that under the constraints of the backhaul link,reasonable location deployment and resource allocation can further improve the throughput of the system.Second,aiming at the time-varying air-ground link status caused by UAV dynamic service in urban environment,this paper proposes a UAV dynamic assisted IoT data forwarding scenario,aiming to use the urban environment air-ground channel line-of-sight probability characteristics to achieve reliable data forwarding and extend sensor service time as much as possible.First of all,this research establishes a UAV-assisted data forwarding system with multiple ground nodes based on a LoS probabilistic channel model that is more suitable for specific urban environments.Under the constraints of sensor transmission energy and transmission data volume threshold,the optimization problem of UAV three-dimensional trajectory and sensor scheduling strategy is proposed.Due to NP-hard,the original problem is decoupled and transformed into a trajectory optimization subproblem that can be solved by continuous convex approximation technology and a scheduling strategy subproblem that can be solved by linear programming,and then the block coordinate descent method is used to obtain the suboptimal solution.The simulation results verify the effectiveness of the proposed algorithm in the urban environment,and further prove that the reasonable UAV trajectory and scheduling strategy can complete the data collection task with as little sensor energy consumption as possible under the constraint of the transmission data threshold.