mmWave on a Farm: Channel Modeling for Wireless Agricultural Networks at Broadband Millimeter-Wave Frequency

 Millimeter-wave (mmWave) spectrum with wide bandwidth provides a promising solution to enable high throughput in next-generation wireless agricultural networks, characterized by swarms of autonomous ground vehicles, unmanned aerial vehicles (UAVs), and connected agricultural machinery. However, channel models at mmWave frequencies in agricultural environments remain elusive. Moreover, agricultural field channels bear notable distinctions from urban and rural macrocellular network channels due to the dynamic crop growth behavior. In this work, a channel model is developed to characterize the large-scale path loss, coherence bandwidth, and link quality under the effect of various environmental factors based on data collected from extensive field experiments. In particular, the wind effect on signal-to-noise ratio is investigated, and the diffuse scattering of electromagnetic waves due to near-canopy propagation at different crop growth stages. Our analysis results demonstrate that (1) during the growing season, the crop canopy surface acts as a ``new ground'' that creates multipath components that result in a higher path loss exponent, which is correlated with the relative height between the crop canopy surface and the radio, (2) the wind results in a half-power drop (3-dB SNR degradation) for an increase of 4~m/s in gust speed due to beam misalignment and increasing scattering, (3) the channel coherence bandwidth increases as the water content in the crop decreases, and (4) the beam-level spatial consistency observed allows for micro-mobility support for agricultural robotic applications. It is also shown that the impacts of humidity and water vapor on the mmWave channel are insignificant in the absence of rain and irrigation. Such characteristics are fundamental for designing advanced channel estimation and signal processing algorithms in advanced agricultural Internet-of-Things solutions.具备大带宽的毫米波（mmWave）频谱为下一代以成群自主地面车辆、无人机（UAV）及联网农业机械为典型特征的无线农业网络实现高吞吐量提供了极具前景的解决方案。然而，农业环境下毫米波频段的信道模型仍尚未得到充分厘清，相关研究仍存在空白。此外，由于作物生长的动态特性，农田信道与城市、农村宏蜂窝网络信道存在显著差异。本研究基于大规模实地实验采集的数据，构建了一款信道模型，用以表征各类环境因素影响下的大尺度路径损耗、相干带宽与链路质量。具体而言，本研究探究了风速对信噪比的影响，以及不同作物生长阶段下电磁波在冠层附近传播时产生的漫散射特性。分析结果表明：（1）在作物生长期，作物冠层表面可等效为"新地面"，其会产生多径分量，进而导致更高的路径损耗指数，该指数与冠层表面与无线收发装置的相对高度呈正相关；（2）当阵风风速每提升4m/s时，由于波束对准偏差与散射加剧，信噪比会出现半功率衰减（即3dB信噪比恶化）；（3）信道相干带宽随作物含水量的降低而增大；（4）观测到的波束级空间一致性可为农业机器人应用的微移动性提供支撑。同时研究表明，在无降雨与灌溉的场景下，湿度与水蒸气对毫米波信道的影响可忽略不计。上述特性可为先进农业物联网（Agricultural Internet-of-Things）解决方案中的高阶信道估计与信号处理算法设计提供核心依据。

搜集汇总

背景与挑战

背景概述

该数据集基于实地实验，为农业环境中的毫米波无线网络提供了信道建模，重点关注大尺度路径损耗、相干带宽和链路质量等关键参数。数据集分析了风速、作物生长阶段和水分含量等环境因素对信道特性的影响，例如风速增加导致信噪比下降，作物冠层表面形成多径分量提高路径损耗指数。这些结果为农业物联网中的信道估计和信号处理算法设计提供了基础。