随机射线方法研究无线电波多径传播特性

把无线电波的物理传播环境建模为随机网格信道,使用最大熵原理得到发生k次反射随机射线在二维传播空间的概率分布.使用随机桥过程产生基本随机变量,以自由布朗桥过程和自由Langevin桥过程为例研究其统计特性,发现基本随机变量服从Rayleigh分布或者x分布随机变量之和的分布.由基本随机变量得到描述无线信道特征参量(包括多径分量的到达时延,幅度增益绝对值和相位等)的表达式.对一个障碍物完全随机分布的二维传播环境的信道特性使用随机射线方法进行仿真分析,得到无线信道的一些特征参量的统计规律,结果与经典的信道特性一致,验证了随机射线方法的有效性.     

无线电波传播中的随机射线及其应用

对建模无线电波传播的随机射线进行了详细的阐述,从随机网格信道引出随机射线的概念,介绍了随机射线的产生背景和分类,并给出一种产生随机射线的数学模型随机桥过程。使用最大熵原理得到发生后次反射随机射线的概率分布。最后介绍使用随机射线建模超宽带室内信道的多径传播轨,在此基础上可以得到信道特性建模的基本随机变量,以及无线电波传播的概率模型等应用。     

无线中继传感网络中异向散射信道的路径损耗特性

使用点渗流网格建模无线传播信道,使用酒徒行走模型建模电磁波在传感信道中的传播过程。酒徒经过k步后,得到某个扇区内取向角均匀分布的随机游走的平均行走距离。在此基础上,得到随机射线在传播空间给定位置的概率分布,最后使用随机射线方法得到了放大传送模式下传感网络的路径损耗模型。该模型中出现指数为1.75的距离r的对数函数形式,以及距离的线性项,该项作为新模型的修正项。     

随机桥方法产生相关时间序列及其应用研究

针对电磁波在无线信道中的传播特点,提出了使用随机桥过程产生具有相关特性的时间序列,由此可以构造出具有特殊概率密度函数,能够用来建模无线信道传播特性的基本随机变量。分别对自由布朗桥过程和有约束布朗桥过程,自由Langevin桥过程和有约束Langevin桥过程产生的随机样本进行研究,使用数值仿真方法分析了基本随机变量的统计特性。结果表明,有约束随机桥过程产生的低跳跃次数随机变量,在概率密度分布上显示出明显的局部偏好性。最后讨论了由时间序列构造的基本随机变量在无线信道建模中的应用。     

非波动方法建模5.3GHz移动通信系统的路径损耗

根据电磁波传播的随机射线理论和渗流网格理论,得到Euclid距离和Manhattan距离度量下的二维随机网格信道中的路径损耗模型,式中参数具有明确的物理意义.使用此模型分析了视距和非视距情况下5.3GHz移动通信系统的功率分布特征.与实测数据进行比较,结果发现使用Euclid距离度量和Manhattan距离度量进行建模,所得的数值解与实际测量结果的均方误差在可以接受的范围内,证明了此模型的准确性和有效性.     

随机桥过程分析街道拐角的无线传播特性

使用随机桥过程研究街道拐角的小尺度衰落和大尺度传播的特性.首先介绍模型,随机桥过程的理论基础,从随机桥过程引入随机射线的概念,利用随机射线建立无线信道分析街道拐角的多径传播特性和大尺度传播特性.然后给出信道的时延分布、多径分量的幅度特性、功率延迟分布,接收机接收波的到达角分布等多径特性参数,并给出路径损耗.仿真结果与参考文献中无线信道测量结果吻合较好,表明使用随机桥过程可以有效地分析街道拐角的无线传播特性.     

一种有多反射特性的超宽带信道建模方法

在几何单反射椭圆信道模型和几何随机信道模型基础上,针对电磁波传播过程中出现的多反射特性,提出一种多反射特性的无线信道建模方法。把该方法应用于超宽带信道研究,可以得到UWB信道的几何随机多反射模型(GSMB)。使用该方法对两个UWB信号传播环境进行仿真分析,仿真得到的UWB信道功率延迟分布与实验结果基本一致,同时也验证了其他研究者关于UWB信道中的成簇现象具有确定性的结论。     

随机桥过程研究短程无线信道的空时特性

使用随机桥过程的样本建模短程无线信道中多径分量的传播轨迹。由随机桥过程的样本构造出基本随机变量,在一定的映射规则下由基本随机变量的样本得到反映无线信道空时特性的多径时延、多径信号抽头增益、多径信号的波达方向等参量。使用随机桥过程的特例布朗桥过程,分别对散射体均匀分布的信道传播环境和有约束的无线信道传播环境的空时特性进行仿真分析。仿真结果表明,在这两种传播环境中,多径分量的波达方向在仰角和水平角维度上均存在一定的局部偏好性,不满足均匀分布的假设。在仰角-水平角-多径分量到达时延这3个自由度的空间中,多径分量的分布表现出一定的规律性。     

用射线跟踪法对室内电波传播进行预测

根据室内电波传播的特点，对室内电波的反射，透射和绕射等传播路径进行了分析，首次考虑了多层介质的反射，透射以及棱角边缘的绕射，建立了基于射线跟踪法的二维和三维传播预测模型，根据这些模型能够计算出室内各处电波传播的路径损耗。计算结果与测量结果符合很好。同时，将二维和三信跟踪预测结果作了比较，结果表明在有些情况下二维跟踪更经济实用。     

矩阵随机过程在短程无线信道空时特性建模中的应用

使用矩阵随机过程对短程无线信道的空时特性进行研究。以随机矩阵的列向量描述信道的仰角自由度,行向量描述信道的水平角自由度。使用自由布朗桥过程产生的样本描述无线信道中的多径分量的传播轨迹,在一定的映射规则下可以得到反映无线信道空时特性冲激响应的传统模型和矩阵随机过程模型。对无线信道的空时特性进行了仿真分析,仿真结果表明,自由布朗桥过程所描述的完全随机的约束环境中,多径分量的波达方向在仰角和水平角维度上显示出一定的局部偏好性。     

On geometric statistics with diversity in multipath scattering channels

This paper studies four aspects of multipath propagation with randomly distributed scatterers: (i) Gaussian and hyperbolic time‐of‐arrival (ToA) probability density functions (pdfs); (ii) theoretical bounds on the ToA pdfs; (iii) geometric pdfs in multipath propagation via Gaussian and hyperbolic scattering channels; and (iv) implementation of selective combining diversity as a method to decrease propagation delay, thus improving transmission performance. The Gaussian and hyperbolic scattering channels are employed to model random scatterers between a base station and a user equipment. One‐dimensional and three‐dimensional results of Gaussian and hyperbolic ToA pdfs are reported. Detailed discussions are given. Copyright © 2012 John Wiley & Sons, Ltd.     

A comparison of two radio propagation channel impulse responsedetermination techniques

A comparison of two radio propagation channel impulse response determination techniques is described. Presented are typical impulse response and transfer functions obtained from each measurement system. Also included for comparison are average impulse response envelopes and cumulative probability distributions for the RMS delay spread of static indoor radio channels calculated from 120 measurements using each system. The comparisons show good agreement between results     

Millimetric wavelengths radiowave propagation for line-of-sightindoor microcellular mobile communications

Discusses millimeter waves for indoor microcellular communications. The results of propagation experiments conducted at 60.4 GHz (the oxygen absorption band) and 38.25 GHz to determine multipath characteristics in a number of indoor microcell channels employing omnidirectional antennas are presented. Cumulative distribution functions for received signal envelope, as well as corresponding power spectra are given. In addition, a comparison between the fading statistics measured at 60.4 GHz and 38.25 GHz under similar conditions is made. The change in multipath characteristics due to the presence of different building materials is also illustrated. A ray model is developed to represent indoor microcell propagation by considering a direct ray plus rays which have undergone single and double reflections from the walls. Specular floor-reflected and ceiling-reflected rays are included when the antennas radiation pattern does not preclude them. Using this simple model, the signal variations and the amplitude of reflected rays with respect to the line of sight (LOS) ray as functions of mobile receiver position are predicted and used to assist in interpreting experimental results. Theoretical results are found to be in good agreement with measured ones, with the model also being used to predict structure-induced root mean square (rms) delay spread along receiver routes in an indoor microcell environment. This parameter is a measure of multipath conditions in a mobile radio channel and is inversely proportional to the maximum usable data signalling rate of a channel     

A new stochastic spatio-temporal propagation model (SSTPM) formobile communications with antenna arrays

In order to evaluate the performance of third-generation mobile communication systems, radio channel models are required. The models should be capable of handling nonstationary scenarios with dynamic evolution of multipath. In this context and due to the introduction of advanced antenna systems to exploit the spatial domain, a further expansion is needed in order to include the nonstationary characteristics of the channel. In an attempt to solve these problems, this paper presents a new stochastic spatio-temporal propagation model. The model is a combination of the geometrically-based single reflection and the Gaussian wide-sense stationary uncorrelated scattering models, and is further enhanced in order to be able to handle nonstationary scenarios. The probability density functions of the number of multipath components, the scatterers' lifetime, and the angle of arrival are calculated to support these features. The input parameters of the model are based on results from measurement campaigns published in the open literature