基于射线跟踪法的粮仓无线信道特性研究

发布时间：2018-04-29 16:04

本文选题：射线跟踪 + 路径损耗　；参考：《河南工业大学》2017年硕士论文

【摘要】：2016年粮食安全成为国家“一号战略”。粮情检测能够及时发现仓储粮堆内出现的温度热点、霉变、异物等异常粮情信息,提前做好粮食安全预警和政策调控。现有的有线传感器粮情检测存在难于布设、监测参数单一、覆盖范围小、难升级等问题。因此,必须尽快研发快速有效的非入侵无损检测方法,提高粮情检测效率,节约检测成本。粮堆是一种与仓型和粮食种类密切相关的散粒体多层结构,大型粮堆储粮高度较高,粮堆各层密度、湿度、温度等分布呈现非均匀性,这导致粮情无线探测技术应用于非均匀粮食介质中时首先要准确估计射频探测信号传输链路的特性,这也是粮堆介质无线数据传输的物理层经典问题。针对此问题,本文深入研究了粮仓信道的电磁特性、粮堆信道的仿真平台的搭建以及粮堆信道的确定性建模等关键技术。主要成果和创新包括如下几个方面:1.从无线信道相关理论出发研究粮堆介质中电波传播的特殊性。根据粮堆温度、湿度和密度与粮食介质介电特性的关系,深入分析电波频率和介质介电特性对粮堆电波传播衰减的影响。通过实测数据和理论分析表明了粮堆湿度和频率是影响电波传播路径损耗的主要因素。2.对比分析统计性、确定性以及半确定性信道建模理论,采用确定性方法中高效精确的射线跟踪算法作为粮仓无线信道的研究方法。提出正向和反向两种射线跟踪信道建模方法,并对粮食介质中各条传输路径上的接收功率、路径损耗、时延和到达角进行定量计算。结果表明两种算法都能较好的反映粮堆中电波的衰减特性,误差范围基本相同。相比复杂度较低效率较高的正向算法,反向算法不仅能得到路径损耗特性,且能获取不同传输路径的相位、时延和极化等信息。3.建立了两种粮仓无线信道仿真平台,能够实现粮仓模型和仿真参数的灵活设置。基于MATLAB反向射线跟踪信道建模平台,研究了粮堆频率、湿度和收发距离对射线幅度分布的影响,并得到平房仓粮堆介质中只需考虑直射径和一次反射径的重要结论。基于电磁仿真软件Wireless InSite正向射线跟踪信道建模平台,得到了与反向射线跟踪算法一致的粮堆介质路径损耗模型。
[Abstract]:Food security in 2016 became a national "strategy number one." The detection of grain condition can detect the abnormal grain information such as temperature hot spot, mildew, foreign body and so on in the storage grain pile in time, and make the food security early warning and policy control well in advance. The existing wired sensors are difficult to set up, single monitoring parameters, small coverage, difficult to upgrade and so on. Therefore, it is necessary to develop a fast and effective noninvasive nondestructive testing method as soon as possible to improve the efficiency of grain condition detection and save the testing cost. The grain heap is a multilayer structure of bulk grain which is closely related to the type and type of grain. The grain storage height of large grain heap is relatively high, and the distribution of density, humidity and temperature in each layer of grain heap is non-uniform. This leads to the accurate estimation of the characteristics of the radio frequency detection signal transmission link when the grain condition wireless detection technology is applied to the non-uniform grain medium, which is also a classical problem in the physical layer of the wireless data transmission in the grain heap medium. In order to solve this problem, the electromagnetic characteristics of granary channel, the construction of simulation platform and the deterministic modeling of grain stack channel are studied in this paper. Major achievements and innovations include the following: 1. Based on the theory of radio channel correlation, the particularity of radio wave propagation in the medium of grain heap is studied. According to the relationship between the temperature, humidity and density of grain stacks and the dielectric properties of grain media, the effects of wave frequency and dielectric properties on the attenuation of electric wave propagation in grain heaps are analyzed in depth. Based on the measured data and theoretical analysis, it is shown that the humidity and frequency are the main factors affecting the propagation path loss of the electric wave. Compared with the statistical, deterministic and semi-deterministic channel modeling theory, the high-efficient and accurate ray tracking algorithm in deterministic method is used as the research method of granary wireless channel. In this paper, forward and reverse ray tracing channel modeling methods are proposed, and the received power, path loss, delay and arrival angle of each transmission path in grain medium are calculated quantitatively. The results show that the two algorithms can well reflect the attenuation characteristics of the electric wave in the grain heap, and the error range is basically the same. Compared with the forward algorithm with lower complexity and higher efficiency, the reverse algorithm can not only obtain the path loss characteristics, but also obtain the phase, delay and polarization information of different transmission paths. Two kinds of silo wireless channel simulation platform are established, which can realize the flexible setting of granary model and simulation parameters. Based on the MATLAB reverse ray tracking channel modeling platform, the effects of grain stack frequency, humidity and receiving distance on the ray amplitude distribution are studied. The important conclusions are obtained that only direct and primary reflection diameters should be considered in the medium of grain bunker. Based on the electromagnetic simulation software Wireless InSite forward ray tracking channel modeling platform, a grain stack dielectric path loss model is obtained, which is consistent with the reverse ray tracing algorithm.
【学位授予单位】：河南工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN92

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