SBR image approach for radio wave propagation in tunnels with andwithout traffic

We propose a deterministic approach to model the radio propagation channels in tunnels with and without traffic. This technique applies the modified shooting and bouncing ray (SBR) method to find equivalent sources (images) in each launched ray tube and sums the receiving complex amplitude contributed by all images coherently. In addition, the vector effective antenna height (VEH) is introduced to consider the polarization-coupling effect resulting from the shape of the tunnels. We verify this approach by comparing the numerical results in two canonical examples where closed-form solutions exist. The good agreement indicates that our method can provide a good approximation of high-frequency radio propagation inside tunnels where reflection is dominant. We show that the propagation loss in tunnels can vary considerably according to the tunnel shapes and the traffic inside them. From the results we also find a “focusing” effect, which makes the power received in an arched tunnel higher than that in a rectangular tunnel. Besides, the deep fading that appears in a rectangular tunnel is absent in an arched tunnel. The major effect of the traffic is observed to be the fast fading due to the reflection/obstruction of vehicles. Additional considerations, such as time delay, wall roughness, and wedge diffraction of radio wave propagation in tunnels are left for future studies     

Modeling radio wave propagation in tunnels with a vectorialparabolic equation

To study radio wave propagation in tunnels, we present a vectorial parabolic equation (PE) taking into account the cross-section shape, wall impedances, slowly varying curvature, and torsion of the tunnel axis. For rectangular cross section, two polarizations are decoupled and two families of adiabatic modes can be found explicitly, giving a generalization of the known results for a uniform tunnel. In the general case, a boundary value problem arises to be solved by using finite-difference/finite-element (FD/FE) techniques. Numerical examples demonstrate the computational efficiency of the proposed method     

多刃峰环境无线电波传播预测的双向抛物方程法

基于迭代双向抛物方程法求解了单刃峰和多刃峰环境下的前向和后向电波传播。对单刃峰,将双向与单向抛物方程法的数值结果做了比较,并分析了刃峰的位置和高度对后向反射场的影响。对多刃峰,采用迭代步进的双向抛物方程法计算相邻刃峰间的电波传播,并将数值结果与单向抛物方程法的结果进行对比。双向抛物方程法能计算出无线电波的前向传播场和后向传播场叠加的总场,比单向抛物方程法的预测结果更准确。     

Experimental characterization of radio wave propagation in hospitals

This paper reports the characterization of radio wave propagation in hospitals. In contrast to other buildings with usual walls, some rooms within hospitals are constructed with special walls that include metallic layers. The structure of the walls depends on the purpose of each hospital room. To consider all the different wall types, measurements were performed in all relevant areas of four hospitals. Rooms, such as operating rooms, X-ray and magnetic resonance tomography (MRT) rooms were taken into account. The measurements were performed at eight discrete frequencies ranging from 42.6 MHz up to 5.2 GHz. In order to investigate accurately the wave propagation properties, several antennas and measurement systems were used. Results show that radio wave propagation characteristics vary from room-to-room. It turned out that it is important to consider the room as a whole when determining the attenuation between adjacent rooms, because a small part of the wall is not enough. In addition to usual wave propagation phenomena such as reflection and transmission, slots and openings give rise to coupling effects through walls containing metallic layers in their structure. The measurement data is useful for hospital designers and hospital engineers.     

电波传播模型的本地化研究

根据目前常用的电波传播模型，研究并提出了对本地化传播模型进行验证评估的方法，使本地化传播模型能更加适合无线电管理工作的需要。     

Hybrid image/ray-shooting UHF radio propagation predictor forpopulated indoor environments

A novel model for indoor wireless communication, based on a dual image and ray-shooting approach, is presented. The model, capable of improved site-specific indoor propagation prediction, considers multiple human bodies moving within the environment. In a modern office at 2.45 GHz, the combined effect of pedestrian traffic and a moving receiver causes rapid temporal fading of up to 30 dB     

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。     

STUDY ON GIS BASED PREDICTION SYSTEM FOR RADIO WAVE PROPAGATION IN UBAN REGION

In this letter, an integrated application of the prediction for radio wave propagation with the Geographic Information System (GIS) is presented and a real prediction system based on GIS is implemented.     

1.2 GHz band wave propagation measurements in concrete building for indoor radio communications

For the design of indoor radio communication or a portable radio telephone system, 1.2 GHz band radio wave propagation characteristics are investigated in a concrete building. Penetration loss through a window, local median variations, and cumulative distributions of received signal levels in a room, reflection coefficient or equivalent dielectric constant and transmission loss of a wall/floor are discussed.     

An indoor radio propagation model considering angles for WLAN infrastructures

Wireless local area network fingerprint‐based indoor location system is a hot topic these years because it needs no extra hardware and is very easy to deploy. However, it demands a database containing the distribution of received signal strength (RSS) of the area of interest,called radio map. Conventionally, we need to grid the area densely and manually measure RSS values on intersections, which will consume a lot of time and human resources. What is worse, change of the environment may render this database totally useless. Our consideration is to measure RSS on a small amount of these intersections and use them to build a radio propagation model. Then, this model can be deployed to predict RSS values of other intersections and reconstruct the radio map. In other words, we only need to collect a very small part the radio map and utilize the radio propagation model to recover the whole one. So far, many models have been proposed, among which the one suggested by Seidel, named floor attenuation factor propagation model, achieves great balance between computational request and accuracy. But it is not compatible with environments in some scenarios. So as to compensate for this deficiency, we take into account the angles formed by signal and surfaces of obstacles, and the results show better compatibility. The proposed model has four parameters that are related to the environments, and our second contribution in this paper is to propose a method to determine them. In fact, after collecting a small part of the radio map, we can estimate these parameters with least square method. Then, these parameters can be used to predict the signal strength at any other points in the same environment, and the whole radio map is rebuilt. According to practical experiments, performance of the radio map built by the proposed model is not as good as the manually collected one, but 80% of collecting labor is saved. Copyright © 2015 John Wiley & Sons, Ltd.     

城市地形对电波传播的影响研究

随着科技的日新月异,我国通信技术得到飞速的发展,无线电波在人们的工作和生活中发挥越来越重要的作用。怎样提升无线电波的应用质量,是相关部门一直探索的课题。为了掌握无线电波在移动通信中的传播规律以及无线信道的特征,文章进行了城市地形对电波传播影响的试验,测量的对象是距离基站2.5 km处8个不同的测量点,测量目的是研究接收的信号电平状态和规律,并对城市地形对电波传播的影响进行研究。     

部分森林覆盖山区电波传播特性预测的快速算法

为提高部分森林覆盖山区电波传播特性预测的时效性,提出了一种基于宽角抛物方程(PE)的快速预测算法。采用PE通过分步傅里叶变换(SSFT)求解;在SSFT步进迭代过程中,根据传播路径上森林的等效介电常数、地形的起伏情况,动态选择PE的水平步长。通过对部分森林覆盖的不规则地形条件下的电波传播特性进行仿真,探讨了该方法的可行性和有效性。结果表明：相比于均匀大步长算法,该方法更准确;而相比于均匀小步长算法,该方法能够保证抛物方程的计算精确度,同时极大地提高计算效率。     

战场环境中的电波传播模型优化选择方法

针对战场级的复杂电磁环境仿真过程中涉及到全频段覆盖、环境影响、仿真速度要求高等问题,提出了一种综合考虑用频装备、环境信息和模型自身特点的电波传播模型选择方法。该方法首先通过频段对用频装备及电波传播模型进行划分,再结合环境信息中降雨量、海拔、植被覆盖率、气候类型、导电特性等参数进行综合分析,最终得到传播模型的优化选择方案。在典型作战场景仿真应用中,该方法为传播模型的合理选择提供了思路,保证了仿真的精度,同时也为电磁环境仿真中传播模型本地化提供了依据。     

An approach to include stochastic rough surface scattering into deterministic ray-optical wave propagation modeling

A new method to include stochastic rough surface scattering into deterministic ray-optical wave propagation modeling is derived. It can be utilized in conjunction with the concept of ray launching. Similar to the Kirchoff formulations, the approach is based on a tangential plane approximation, i.e., it is applicable to surfaces with gentle undulations, whose horizontal dimensions are large compared to the incident wavelength. However, in contrast to the Kirchoff models, which are only valid for either slightly rough or very rough surfaces, the proposed stochastic scattering approach includes both the coherent and incoherent components at the same time. The purely deterministic ray-based modeling is expanded by a "stochastic" component, allowing, for the first time, to account for nondeterministic scattering in ray-optical wave propagation modeling.     

Prediction of mobile radio wave propagation over buildings ofirregular heights and spacings

Two models of mobile radio wave propagation over buildings are presented. The first, the flat edge model, provides a simple yet accurate representation when buildings are assumed to be of constant height and spacing. The second model combines the first with a rapid new method of calculating multiple edge diffraction to allow deterministic predictions with arbitrary buildings and spacings. This allows predictions to be made with real building data, and the effect of building variations on location variability of the received signal to be assessed. Both models are compared with measurements made in suburban areas in the 900 and 1800 MHz bands and excellent agreement is obtained     

Fractional calculus approach to the acoustic wave propagation with space-dependent sound speed

In this note we study the space-fractional wave equation in relation to the propagation of acoustic waves with space-dependent sound speed. We take into account this variability, by using the space-fractional derivative in the classical wave equation. In order to give a clear comprehension of this mathematical formulation, we discuss the analytic solution of a simple boundary value problem (BVP) by an operational method, finding a fractional oscillating spatial profile.     

基于PETOOL的大气波导环境下舰艇通信电波传播仿真分析

针对面向大气波导环境下的舰艇超视距大容量通信以及通信盲区、通信隐蔽性研究需求,在分析大气波导抛物方程模型的基础上,利用首次同时实现单向和双向抛物方程算法的PETOOL电波传播的天线高度、频率等影响因素进行仿真研究,仿真结果可为设计海上大容量超视距通信系统和科学运用舰艇通信设备提供参考依据。     

基于抛物方程法的部分森林覆盖山区电波传播分析

基于Fourier分步步进法的抛物方程模型求解了山区不规则地形部分森林覆盖环境的电波传播,并分析了森林对电波传播的影响.模型中为了简化边界条件,地形用分段线性函数来近似.然后预测了一个山区部分针叶林覆盖环境的电波传播,得到的结果与实测数据进行对比,二者吻合很好.最后对算法的稳定性与误差进行了分析,本文的模型能处理不规则地形、森林等复杂环境且算法效率高.