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[转载]【无人机】【2019.09】基于无人机的无线通信研究

已有 188 次阅读 2020-10-20 18:21 |系统分类:科研笔记|文章来源:转载


本文为比利时鲁汶大学(作者:M. Mahdi AZARI)的博士论文,共182页。

 

无人机(UAV)由于其快速和经济高效的部署,在许多应用中得到越来越多的应用。无人机可以作为辅助基础设施为地面用户提供无线服务,或者它们可能需要从地面进行无线连接以实现安全可靠的运行。对于这些需求,确实需要一个充分的无人机集成到地面的无线网络

 

本文以无人机辅助通信组网和网络辅助无人机通信两个主要内容来研究这种集成系统。前者的目标是为地面设备提供数据交换或定位服务。在后者中,蜂窝网络用于无人机连接的可能性受到质疑,现有的地面网络旨在帮助实现可靠的地对空或空对空连接。特别考虑了四种新的场景:无人机作为空中基站为地面用户服务,无人机作为空中锚来定位地面设备,无人机充当空中蜂窝用户,最后是蜂窝式无人机通信。通过这些场景,我们解决了无人机无线通信和联网中的几个重要问题,包括:地面无人机信道特性、设计自由度、无人机组网的独特限制、用户和网络级性能、无人机的优化部署以及重要的设计指南。在考虑无人机基站时,我们提供了一个统一的信道模型,该模型集成了地对地和空对地模型,使我们能够分析混合地面无人机网络的性能。我们开发了一个分析框架来研究无人机的覆盖和效率。研究了无人机高度、功率控制等系统参数对用户性能和覆盖范围的影响。为了提高链路可靠性、扩大地面覆盖范围,研究了无人机协同通信。

 

结果表明,加入地面中继不会改变无人机的最佳高度。然后研究了无人机地面节点定位问题。提出了一种新的基于接收信号强度的无人机高度和城市障碍物对定位误差影响的RSS方法。利用这个框架,我们可以优化无人机的高度轨迹和无人机的数量,以获得最优的定位性能。我们特别指出,与地面设备相比,空中设备能够提供显著更优的RSS定位精度。接下来,讨论了将地面蜂窝网络用于无人机超视距(LoS)连接的可行性。在下行链路中考虑蜂窝基站服务的无人机,分析了无人机与地面用户共存时的性能。我们推导了覆盖概率、可实现吞吐量和区域频谱效率等关键指标的精确表达式。无人机的主要性能限制因素得到了识别,并提供了基于用户和网络的解决方案,以便将无人机和谐地集成到此类网络中。我们进一步研究了添加无人机用户时网络异构性和密度的影响。最后,对蜂窝式无人机通信进行了研究,深入了解了无人机与地面用户在共享上行频谱时的相互作用。我们的分析框架包括一个三维基站天线方向图和与距离相关的功率控制策略。推导了地面用户和无人机对无人机链路性能的精确表达式。我们的研究结果表明,与地面效应相比,无人机干扰对地面用户的影响是有限的。

 

Unmanned aerial vehicles (UAVs) or theso-called drones are increasingly used in many applications thanks to theirrapid and cost-effective deployments. UAVs can be used as complementaryinfrastructure to provide wireless services for the ground users or they mayrequire wireless connectivity from the ground for a safe and reliableoperation. For these, indeed, an adequate UAVs integration into ground wirelessnetworks is required. In this thesis, we investigate such integrated system byaddressing several important research problems through two main paradigmsnamely UAV-assisted communication networking and network-assisted UAVcommunication. In the former, UAVs aim to serve ground devices for dataexchange or localization services. In the latter, the potential use of cellularnetworks for UAVs connectivity is questioned, where the existing groundnetworks aim to assist a reliable ground-to-air or air-to-air connectivity. Inparticular, four emerging scenarios are considered: UAV acting as aerial basestation to serve ground users, UAV acting as aerial anchor to localize grounddevices, UAV acting as aerial cellular user, and finally cellular UAV-to-UAVcommunication. Through these scenarios we address several of important concernsin UAVs wireless communication and networking including: ground UAV channelcharacteristics, design degrees of freedom, unique constraints in UAVsnetworking, user and network level performance, optimal deployments of UAVs andimportant design guidelines. When considering UAV base stations, we provide aunified channel model that integrates ground-to-ground and air-to-groundmodels, enabling us to analyze the performance of hybrid ground-UAV networks.We develop an anlytical framework for the study of UAV’s coverage andefficiency. The impacts of various system parameters such as UAV altitude andpower control on the user performance and coverage area are investigated.Cooperative communication is investigated for the link reliability enhancementand ground coverage extension.

It is shown that the inclusion of groundrelays does not change the optimal UAV’s altitude. We then study the case ofground node localization using UAVs. A novel framework that takes into accountthe impact of UAV’s altitude and urban blockages in localization error usingreceived signal strength–RSS method is proposed. Using this framework we areable to optimize the UAV’s altitude trajectory and the number of UAVs for thehighest localization performance. We particularly show that aerial anchors arecapable of providing significantly higher RSS-localization accuracy compared toground anchors. Next, the feasibility of using ground cellular networks forUAVs beyond visual line-of-sight (LoS) connectivity is addressed. We considerUAVs served by cellular base stations in downlink and analyze the UAVperformance coexisting with the ground users. We derive exact expressions forthe key metrics named coverage probability, achievable throughput and areaspectral efficiency. The major UAVs performance limiting factors are recognizedand user and network based solutions are provided for a harmonic integration ofUAVs into such networks. We further investigate the impact of networkheterogeneity and densification when adding UAV users. Finally, cellularUAV-to-UAV communication is studied which provides an in-depth insight into theinterplay between UAVs and ground users when sharing uplink spectrum. Ouranalytical framework includes a 3D base station antenna pattern and distancedependent power control policy. We derive exact expressions for the groundusers and UAV-to-UAV link performance. Our results show that for the examinedcases of study the impact of UAVs interference on the ground users is limitedas opposed to ground effects on the UAVs.

 

1. 引言

2. 建模基础

3. 服务地面用户的无人机空中基站

4. 定位地面节点的无人机

5. 蜂窝网络中的空中无人机用户

6. 蜂窝网络中的UAV-to-UAV通信

7. 结论与展望


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