面向农业应用的433MHz无线信号传播特性研究

发布时间：2018-04-19 06:26

本文选题：精准农业 + 软件无线电　；参考：《北京邮电大学》2015年硕士论文

【摘要】：如何在有限的农业资源基础上,提高农业的生产效率、经济效益与环境效益已经成为我国农业精细化进程所必须要解决的问题。依托先进的信息技术成为实现这一目标的重要手段。在众多的信息化技术中无线传感器网络技术无疑是农业现代化研究最热门的方向之一。无线传感器网络技术包括了传感器技术、微机电系统技术、无线通信技术、嵌入式计算技术和分布式信息处理技术,它们具有功耗低的特点。也正是由于低功耗使得节点间的收发不像传统的无线通信一样可以覆盖较大的范围,当应用环境不一样时,无线传感器网络的覆盖特性会有很大的不同。农业环境具有地势多样、天气状况复杂、面积庞大、农作物生长周期长等特点,这些特点给无线传感器网络技术的应用带来了挑战。在实际环境下部署无线传感器网络前需要对信号的传播环境有细致的了解，，才能保证网络的覆盖性。基于这点,本文从两个角度来分析测量农田环境下信号的传播特性。第一,我们使用无线传感器节点和频谱仪测量冬小麦在三种典型的生长期下433MHz信号的路径损耗变化特性,整个测量工作在国家精准化农业基地完成,完成测量工作之后,利用matlab对所得数据进行曲线拟合和回归分析,得出农业环境下433MHz信号的大尺度传播模型,然后将所得模型与我们在室内和室外空旷环境测量总结的模型进行比较,分析麦田环境对信号传播特征的影响；第二,使用软件无线电平台GNU Radio和USRP设计多径时延特性测量系统,系统由两台USRP组成,发送端发送M序列,接收端利用相同的M序列对接收信号进行滑动相关处理,提取相关后信号的功率延迟分布,通过功率延迟分布得到信号的多径时延和多径强度。在完成系统设计后,在北京邮电大学校园内进行了室外LOS和NLOS测试,得到两种信道条件下433MHz无线信号的功率延迟分布,利用功率延迟分布得到该环境下信号的多径传播特性,验证了测量系统的有效性。
[Abstract]:How to improve agricultural production efficiency, economic benefit and environmental benefit on the basis of limited agricultural resources has become a problem that must be solved in the process of agricultural refinement in China.Relying on advanced information technology has become an important means to achieve this goal.Wireless sensor network (WSN) is one of the hottest research directions in agricultural modernization.Wireless sensor network technology includes sensor technology, MEMS technology, wireless communication technology, embedded computing technology and distributed information processing technology, which have the characteristics of low power consumption.Because of the low power consumption, the transceiver between nodes can not cover a large range like traditional wireless communication. When the application environment is different, the coverage characteristics of wireless sensor networks will be very different.The agricultural environment has the characteristics of diverse terrain, complex weather conditions, huge area and long crop growth cycle. These characteristics have brought challenges to the application of wireless sensor network (WSN) technology.In order to ensure the coverage of wireless sensor networks, it is necessary to have a detailed understanding of the signal propagation environment before deploying wireless sensor networks in the actual environment.Based on this, this paper analyzes the signal propagation characteristics in the field environment from two angles.First, we use wireless sensor nodes and spectrometers to measure the path loss characteristics of winter wheat 433MHz signals during three typical growth periods. The whole measurement was completed at the National Precision Agriculture Base.By using matlab curve fitting and regression analysis, the large scale propagation model of 433MHz signal in agricultural environment was obtained, and then the model was compared with the model that we summarized in indoor and outdoor open environment.The effects of wheat field environment on the signal propagation characteristics are analyzed. Secondly, a multi-path delay measurement system is designed using the software radio platforms GNU Radio and USRP. The system is composed of two USRP, and the transmitter transmits M sequence.The receiver uses the same M sequence to carry on the sliding correlation processing to the received signal, extracts the power delay distribution of the correlated signal, and obtains the multipath delay and the multipath intensity of the signal by the power delay distribution.After completing the system design, outdoor LOS and NLOS tests were carried out on the campus of Beijing University of posts and Telecommunications. The power delay distribution of 433MHz wireless signals was obtained under two channel conditions. The multipath propagation characteristics of the signals in this environment were obtained by using the power delay distribution.The validity of the measurement system is verified.
【学位授予单位】：北京邮电大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S126;TN92

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