无人机自组织网络窄波束定向接入理论与技术研究

The UAV (Unmanned Aerial Vehicle) ad hoc networks can provide wireless connections for the combat units in the beyond-visual-range combat through the manner of “hot area cover”. To meet the emerging demand for improving the stealth performance of the UAV in the beyond-visual-range fighting, there is a clear trend towards the use of narrow-beam directional communication mode in the next generation advanced UAV data link system, which will has the good RF stealth performance and a strong anti-interference ability. According to the features and advantages of the narrow-beam directional communication mode, this project proposes an over all design of the narrow-beam directional medium access control (MAC) protocol for UAV ad hoc networks based on the synchronization of all the nodes in the network. The main contents of this project include three parts. First, this project is going to propose a master-slave synchronization protocol based on the narrow-beam directional communications of the nodes. This protocol can be used to provide time synchronization for all the nodes in the multi-hop network. Second, this project divides the neighbor discovery process into two phases: neighbor beam alignment and neighbor beam tracking. Then this project will propose a high efficient neighbor discovery method based on the analyzing of the beam alignment probability and the estimation of the beam alignment duration of the two neighboring nodes. Finally, this project will propose the concept of the directional link concurrent graph and accordingly to explore the new ideas for modeling and analyzing the MAC layer throughput of the narrow-beam directional MAC protocol. This project aims at providing the theory foundation and design methodology for the narrow-beam directional MAC protocol of the UAV ad hoc networks. The outcomes of the project are expected to significantly promote the future development of the stealthy data link system and the space-sky-land incorporated information combat system.

无人机自组织网络通过空中无线“热区”覆盖的方式，为信息化条件下的超视距战争提供通信保障。为了提升超视距对抗环境中无人机的隐身性能，下一代先进的无人机数据链系统采用射频隐身性能好、抗干扰能力强的窄波束定向通信方式已成为必然。本项目紧密结合窄波束定向通信方式的特点，充分发挥其优势，提出了基于全网同步的窄波束定向接入协议设计总体方案。主要研究工作包括：①在节点窄波束定向侦听和收/发的条件下，设计多跳主从同步协议，支持全网节点逐级完成精同步；②将邻居发现过程分为波束对准和波束跟踪两个阶段，提出基于波束对准概率分析和对准持续时间估计的邻居发现方法；③采用定向链路并发图描述实现定向并发传输的约束条件，探索窄波束定向接入协议MAC吞吐量建模分析的新思路。本项目旨在为无人机自组织网络窄波束定向接入协议设计提供基础理论和方法，为我国未来隐身数据链系统研制、天空地一体信息化作战体系构建提供技术支持和储备。

本项目针对无人机自组织网络窄波束定向接入理论与技术展开研究，取得了一系列原创成果：（1）设计了无人机自组织网络窄波束定向主从同步协议。同步过程分为粗同步和精同步两个阶段。粗同步阶段，主节点通过定向持续广播粗同步帧发起同步过程；精同步阶段，从节点与主节点通过精同步请求帧和精同步应答帧的定向交互，消除时钟偏移和时钟漂移，实现网络时间同步。同时，针对从节点竞争发送精同步请求帧的过程进行数学建模，得到了精同步竞争参数最优取值，为同步效率优化提供了理论支撑。（2）针对窄波束定向天线的特性，提出了基于随机退避与三次握手策略的邻居发现机制。结合无人机节点运动模型，提出了基于链路持续时间预测的邻居波束跟踪机制。该机制保证邻居节点在一定波束偏差范围之内发起控制帧交互，从而通过DOA估计自动调整天线波束的方向，实现波束跟踪。根据节点间链路持续时间的分布函数，确定了跟踪周期长度、邻居发阶段的子时隙数量与网络连通状况、网络传输效率之间的关系，为邻居发现参数设置提供了依据。（3）针对窄波束定向接入条件下的MAC吞吐量建模展开研究。提出了定向链路并发图的方法描述定向并发传输的约束条件，并将MAC吞吐量最大化的问题描述成带约束的多商品流问题。分析了不同网络拓扑条件下，天线波束宽度与MAC吞吐量理想上界之间的关系。进一步提出了基于定长时隙的随机定向接入协议四维马尔可夫链模型，对随机定向接入条件下的MAC吞吐量进行建模与分析。通过与定向并发传输条件下的MAC吞吐量理想上界的对比，揭示了全网同步定向接入方式在窄波束条件下应用的优势。（4）研发了具有自主知识产权的无人机自组织网络半实物仿真平台，对协议性能进行测试。项目组在IEEE CL，IEEE TWC，IEEE MSN等期刊和会议发表学术论文25篇；申请国家发明专利25项，已获授权11项，向企业转让发明专利3项；培养硕士20人；获国防技术发明三等奖，南京市优秀发明专利奖各1项。项目研究工作已达到了计划书中的预期目标。