【作者】 刘忠玉；

【导师】 郭立新；

【作者基本信息】 西安电子科技大学 ， 无线电物理， 2013， 博士

【摘要】 室内外无线网络设备市场不论是在商用方面还是在民用方面的发展都被寄予厚望室内外传播信道特性的全面调查研究是设计和实现这种应用的一个基本步骤，这使得使用能精确预测室内外环境下的传播信道特性的传播模型成为必要传统的传播模型适用于较大场景，该模型一般基于经验模型和半经验模型然而，随着通信量的稳定增长，蜂窝小区也越来越小，传统的传播模型已经不能提供准确的传播预测作为确定性算法的射线跟踪成为了传统模型的合适替代工具，并被广泛地使用射线跟踪一般用于对无线通信系统信道特性的定点预测的计算，该技术能提供多径接收情况时的时延和到达角信息因此，射线跟踪能为无线电波传播预测和网络规划提供可靠的理论依据本文针对室内微微小区和街道微小区环境的几何信息存储格式，进行合理的场景建模，在此基础上基于射线跟踪技术实现对这两种场景下的无线信道预测，并系统地研究了覆盖预测的加速技术主要的研究内容及取得的研究成果如下：1.介绍了射线跟踪算法的理论基础：几何光学和一致性绕射理论；详细给出了室内微微小区和街道微小区环境下射线跟踪算法中牵涉到的主要概念和基本定义，在此基础上，提出了一种新型虚拟源树理论；详细地给出了射线跟踪能预测的无线信道参数及其对应的计算公式2.提出了针对复杂典型室内场景的环境建模方法，并设计出了一种能用于室内三维射线跟踪算法的新型标准环境信息格式；系统阐述了针对室内所有传播路径的射线分类技术，并详细描述了实现三维室内射线跟踪覆盖预测的操作步骤；实现了室内微微小区环境下对于窄带和宽带结果的准确预测3.基于对三维极面扫描方法的基本思想的分析，避免了在极面扫描算法中出现的不必要的重复计算；通过仿真计算分析了构建虚拟源树的效率，提出了使用功率阈值结合限制数方法来提高构建虚拟源树的效率，以此来避免对无效射线路径的跟踪；针对绕射的特殊传播机制和接收点与周围环境几何信息间的关系，设计了对应的数据结构，来提高建立虚拟源树过程中的遮挡判断效率4.给出了典型街道微小区场景下的几何环境信息的建模方法，介绍了环境信息的主要来源；针对存储街道微小区环境信息的数字地图，描述了新型室外射线跟踪模型的主要思路，概述了基于该新型射线跟踪技术的室外预测的操作流程，详细描述了构建虚拟源树的具体实现步骤以及如何在建立虚拟源树的过程中避免不必要的遮挡判断；实现了街道微小区环境下对于窄带结果的准确预测5.根据准三维射线跟踪算法的特性，提出了建筑物几何信息的智能预处理技术；研究了建立虚拟源树过程中与反射源相关的加速技术，使用了新的朝向面集合概念和改进的二维极面扫描算法，解决了已有射线跟踪算法中构建虚拟源树效率不高的问题；提出了反射源和绕射源可见接收位置的加速方法和单射线的阈值控制技术，提高了室外大区域覆盖预测时的预测效率更多还原

【Abstract】 In the forthcoming years, the market for indoor and outdoor wireless networkingfacilities is expected to grow considerably in both commercial and domestic sectors.Thus, a thorough investigation of indoor and outdoor propagation channelcharacteristics represents a fundamental step toward the design and the implementationof such applications. This makes it necessary to have an accurate propagation model topredict propagation channel characteristics in indoor and outdoor environment.Traditionally, propagation models based on empirical and semi-empirical models havebeen used for large scenarios. However, as the traffic is constantly growing, the cellssize has decreased and current models cannot provide good predictions. As aconsequence, deterministic methods as ray tracing are a good alternative to be used. Raytracing is a commonly used computational method for site-specific prediction of theradio channel characteristics of wireless communication systems. The ray tracingtechnique inherently provides time delay and angle of arrival information for multipathreception conditions. So, the ray tracing can provide the reliable theory basis forradio-wave propagation prediction and network planning.According to the format storage of geometric information for both indoor picocellenvironment and street microcell environment, this dissertation presents a appropriatemodeling approach. On this basis, the successful prediction of radio channel is achievedthrough using the ray tracing technique in the two environment, then the acceleration ofcoverage prediction is systematically studied. The main contents and innovations are asfollows:1. Two theoretical foundations of ray tracing are introduced at first: geometricaloptics and uniform theory of diffraction. The main concepts and basic definitionsinvolved in the ray tracing algorithm in indoor picocell and street microcell aredescribed in detail. Then, the new virtual source tree is proposed. Moreover, all the adiochannel parameters predicted by ray tracing and the corresponding computationalformulas are also shown.2. A modeling approach in typical complex indoor environments is presented. And,a new storage format of environment information used in three-dimensional ray tracingmethod is designed. The ray-path classification technique for all the indoor propagationpaths is elaborated. Then, the operation procedure of coverage predition based on theproposed threed-dimensional ray tracing is represented in detail. The results indicatethat the proposed prediction model works well for both narrowband and wideband prediction for indoor picocell applications.3. Based on the study of the main idea of the three-demensional polar sweepalgorithm, some repeated judgments can be avoided. Through the analysis of theefficiency of virtual source tree creation, the method using power threshold control andlimit number is proposed to improve the efficiency of virtual source tree creation andavoid tracing the void ray paths. Considering the particularity of the propagationmechanism for diffraction and the relationship between receiver points and geometricinformation of surroundings, the corresponding data structure is designed, resulting inan improvement of the efficiency of intersection tests.4. A modeling approach for the geometric information in typical street microcellenvironments is presented. Also, the source of these environment information isintroduced. Utilizing the digital map to store the environment information of streetmicrocell, the main idea of the novel outdoor ray tracing model and the correspondingoperation procedure are described in detail. Furthermore, the implementation procedureof creating virtual source tree and the avoidance of unnecessary intersection tests aregiven. The results indicate that a good prediction accuracy for both narrowband andwideband prediction for indoor picocell applications is achieved.5. According to the characteristic of the quasi three-dimensional ray tracingalgorithm, intelligent preprocessing techniques for the geometric information ofbuildings are improved. During the process of creating the virtual source tree, someacceleration techniques in regard to reflection source are investigated. A very importantconcept orientation face set and improved polar sweep algorithm are used, solvingthe problem that the efficiency of creating the virtual source tree is not high in theoriginal ray tracing method. The handling of visible receivers for both reflection anddiffraction sources and the threshold control of each ray path are proposed. On this basis,the efficiency of coverage prediction over a large area is well improved.更多还原