移动网络接入的无人机通信系统建模与干扰管理

Connecting unmanned aerial vehicles (UAVs) to cellular networks can reuse existing base stations (BSs) and communication protocols, and thus effectively improve communication performance and remote control distance of the UAV. High UAV altitude results in high probability of line-of-sight (LOS) link to the ground, and hence likely to communicate/interfere with a large number of nearby BSs. Therefore, it is necessary to re-evaluate the UAV’s performance when connecting to existing cellular networks whose design is mainly for terrestrial communications, including network planning, frequency reuse pattern, BS antenna pattern, etc.; and further devise effective techniques to manage the severe aerial-ground interference in order to provide 3-dimensional (3D) coverage. This project targets at system modeling and interference management from network design perspective, and investigates the following three sub-projects. 1) To evaluate system overall performance, generalized Poisson binomial (GPB) distribution and the new “generalized Poisson multinomial (GPM) distribution” are studied and leveraged to characterize the interference distribution and further reveal fundamental performance trade-off with key system parameters. 2) For a deployed UAV, model-based and model-free methods are investigated to construct 3D Channel Gain Map (CGM), based on which the UAV’s position and configuration are optimized using optimization theory to improve the communication quality and reduce interference. 3) For multi-UAV systems, we propose to equip the UAVs with directional antennas to confine the interference range, and apply stochastic geometry to characterize the system throughput; distributed optimization and game theory are further leveraged to design distributed interference management mechanism, in order to reduce network control overhead and increase system capacity. Our research results will provide theoretical basis and technical support for the next generation heterogeneous network with hybrid aerial-ground users, and promote the development of related standards and industry.

无人机接入移动网络可以复用现有基站和通信协议，提升对地通信性能和操控距离。无人机高度造成较大概率的视距链路，使其可能接入/干扰大范围基站；现有基站天线和网络规划等为陆基通信设计，需重新评估并有效管理空中-地面干扰，以提供三维空间覆盖。本项目针对系统建模与干扰管理，从网络设计层面重点研究三个内容1)针对整体性能，研究和利用广义泊松二项分布和新的“广义泊松多项分布”，分析干扰分布、系统性能与主要参数的本质关系2)针对现场的无人机，采用建模、非建模方法构建三维信道增益地图，挖掘其结构特征并结合优化理论，优化无人机部署与配置，提升性能降低干扰3)针对多无人机系统，提出无人机配置定向天线以缩小干扰范围，运用随机几何分析通信容量，进一步用分布式优化、博弈论等设计分布式干扰管理机制，简化网络控制，提升通信容量。研究成果将为下一代三维空间混合用户的异构网络提供理论依据与技术支撑，推动相关标准及产业化发展。

针对新兴的网联无人机通信系统，本项目研究的核心问题是如何建立三维通信系统模型，研究并刻画系统整体性能以及关键参数的作用，进而指导网联无人机通信系统的优化部署。首先，我们考虑了基站天线的三维增益模式、无人机-基站三维信道特性、大范围临近基站的通信负载情况等，研究和利用了广义泊松二项分布以及新的“广义泊松多项分布”，建立了网联无人机三维系统模型并分析系统性能与主要设计变量与系统参数的关系，能够从整体上优化系统参数、指导系统升级与再设计。接着，我们提出了无线电地图的构建方法和应用框架，并针对网联无人机三维信道特点以及地面基站实际天线模式和通信负载情况，构建了三维无线电地图并辅助无人机优化部署，以此提升性能降低干扰。进一步地，针对多无人机通信系统，我们提炼了新的设计考量和赋能技术，包括利用现有传统基站的固定天线模式来直接服务空中-地面混合用户，以及基站升级后利用三维波束成形来针对服务特定用户并降低相互干扰。另外，我们还针对具体城市三维地形图，提出深度强化学习方案实现对多无人机空中平台的联合优化部署。最后，在完成预定计划的基础上，我们拓展研究了广域物联网的系统分析与优化部署、智能反射面辅助立体通信与优化部署等，将本项目探索形成的系统建模、信道统计分析、优化部署策略等一整套研究思路与方法进行了延伸，力求在无人机空中物联网、智能反射面辅助立体通信等方向上实现创新与融合应用。本项目的研究有助于丰富三维空间混合异构网络的理论与技术，提供基础的系统建模与分析框架、解决关键干扰问题的新角度与新方法，以及拓展应用的思路与方向。研究成果对无人机通信、立体通信、空中-地面混合物联网的性能分析与优化部署具有积极的理论指导意义和实用价值，同时将推动相关标准、技术及产业化的发展。