【作者】 李林；

【导师】 罗锴；

【作者基本信息】 华中科技大学 ， 信息与通信工程， 2022， 硕士

【摘要】 无人机辅助通信是应对应急通信场景下传统移动通信基站架设成本过高、灾区交通运输环境恶劣等问题,恢复灾区临时通信服务的一项极具潜力的方案。其中,无人机的空间机动性使其在应急通信场景中具备广阔的应用前景。针对现有相关研究未利用无人机的高度维自由度以及未考虑无人机的回程传输过程这两个问题,本文开展应急通信场景下同时考虑用户接入和无人机回程传输过程的高能效无人机辅助通信策略研究。首先,本文介绍了无人机辅助通信中的一种空对地(A2G)信道模型。针对该模型,分析了空对地信道路径损耗随无人机高度、无人机与地面用户的水平距离之间的变化规律。根据这一规律,建立了最小化空对地信道路径损耗优化模型。为求解该模型,采用数形结合的方法,得到了无人机的最佳部署高度随其距地面用户水平距离之间的关系。其次,研究了应急场景中的单无人机辅助通信策略。构建了基于闭合路径巡航的单无人机辅助通信系统模型。为表征无人机的巡航路径,提出了同时兼顾建模复杂度和无人机运动时变特性的准静态假设条件。介绍了一种无人机飞行功耗模型以描述无人机在巡航过程中的飞行耗能情况。为保证最大化系统能量效率时无人机回程能效也足够高,提出了不同于传统系统能效度量的一种新的系统能效度量,由此建立了单无人机场景中的系统能效优化模型。为求解该模型,提出了一种基于迭代的求解算法。仿真结果验证了所提算法的收敛性和有效性。最后,研究了应急场景中的多无人机辅助通信策略。构建了基于定点覆盖的多无人机辅助通信系统模型。沿用所提的新系统能效度量,建立了多无人机场景中的系统能效优化模型。为求解该模型,提出了一种基于迭代的求解算法。仿真结果验证了所提算法的收敛性和有效性。更多还原

【Abstract】 Unmanned Aerial Vehicle(UAV)-assisted communication technology,as a highly promising solution to the problem how to temporarily restore communication services in disaster areas,can effectively tackle with troubles such as high cost of building traditional mobile communication base stations and the awful post-disaster traffic conditions under emergency communication scenarios.Meanwhile,the mobility of UAV greatly facilitates the broad application of UAV in emergency communication scenarios.However,there are still two problems in existing relevant research works: neither the height of UAV nor the procedure of the backhaul transmission of UAV is considered.Therefore,an energy-efficient UAV-assisted communication strategy in emergency communication scenarios is studied in this dissertation with consideration of both uplink access of user and backhaul transmission of UAV.Firstly,an Air-to-Ground(A2G)channel model for UAV-assisted communication is introduced in this dissertation.For this model,the impact of the height of UAV and the horizontal distance between UAV and the ground user on the path loss of A2 G channel is analyzed.Based on this,an optimization model of minimizing the path loss of A2 G channel is formulated.With combination of number and shape,the relationship between the optimal deployment height of UAV and its horizontal distance from the ground user is obtained.Secondly,single UAV-assisted communication strategy in emergency scenarios is designed.A system model where the UAV cruises along a closed path is presented.To describe the trajectory of the UAV,a quasi-static hypothesis that takes into account both the modeling complexity and the time-varying characteristics of the motion of the UAV is presented.To compute energy consumption due to the motion of the UAV,a flight power consumption model is introduced.To ensure that the energy efficiency(EE)of backhaul transmission of UAV is high enough when the EE of the system is maximized,a new metric for the EE of the system is proposed in this dissertation,following which an EE optimization problem in the single UAV scenario is formulated.an iteration-based solution algorithm is further proposed to solve this problem.Simulation results verify the convergence and effectiveness of the proposed algorithm.Finally,multiple UAVs-assisted communication strategy in emergency scenarios is designed.A system model where different UAVs serve different ground users at different position over disaster area is presented.Along with the aforementioned proposed metric,an EE optimization problem in the multiple UAVs scenario is formulated followed by an iteration-based solution algorithm to solve it.Simulation results verify the convergence and effectiveness of the proposed algorithm.更多还原