射线跟踪模型在LTE无线网络规划中的应用

随着LTE的部署与发展,传统的无线传播模型已无法满足LTE实际规划的需要。文章首先分析了射线跟踪模型在LTE无线仿真的准确性,并在实际网络规划中加以应用。测试结果证明,基于射线跟踪模型的仿真对LTE试验网基站布局的影响及其指导意义。     

室内射线跟踪关于反射次数的收敛性分析

由于射线跟踪所需时间随着反射次数增加而迅速增加,反射次数的上限值对于室内射线跟踪的精确度和效率至关重要。因此,本文开展了一个基于统计分析室内场景数据的射线跟踪收敛性研究。通过统计场景中的分布特征,分析射线跟踪不同反射路径的概率,研究接收功率关于射线跟踪最大允许反射次数的收敛关系,得出最优的反射次数上限值,实现优化室内射线跟踪的效率和精确度。将本文模型收敛性与射线跟踪仿真结果的收敛性参数进行对比,在同样计算精确度下,本文模型的收敛结果与射线跟踪仿真收敛结果一致,验证了本文模型的准确性。     

基于射线跟踪的小区信号强度估计

基于经验模型的无线信号强度估计方法无法针对具体物理场景,估计结果精度低,无法满足移动通信网络规划和优化的需要。射线跟踪技术能依据场景信息跟踪电波传播路径,但现有的反向跟踪方法在进行室外成片区域信号强度估计时复杂度高,无法实用。为提高估计结果的精度,降低估计方法的复杂度,提出了一种正向跟踪信号强度估计方法,将基站天线处发射的电磁波模拟成离散的射线,在考虑建筑物形状、分布信息的基础上采用基于网格的搜索算法跟踪射线路径,在接收点处对反射、绕射射线接收合并,最终得到基站覆盖区域的信号强度分布。仿真结果表明该方法的场强估计结果和实测数据吻合程度远大于经验模型估计方法,并且80%左右的估计结果和实测数据的误差在12 dBm以内,可应用于移动通信网络规划和优化。     

一种无线网络规划中的室外射线跟踪模型

针对射线跟踪技术在无线网络规划中实现的困难,提出了一种基于射线跟踪技术的室外传播模型。模型在地理建模部分吸取了数字图像处理学的方法,并采用了高效的射线发射、加速及跟踪算法,通过合理的结果收集设计,有效地降低了射线跟踪技术的复杂度,提高了计算速度。通过仿真证明了模型的准确性和有效性,为射线跟踪技术在无线网络规划工程中的实际应用提供了借鉴。     

基于三维射线跟踪模型的无线网络仿真研究

无线电磁传播模型是无线网络仿真的基础,传播模型的优劣直接决定着无线网络仿真对网络规划方案、评估等方面的作用。而三维射线跟踪模型则被认为是当今无线网络仿真向精细化、准确化、科学化发展方向的主流趋势,它的引入将对无线网络仿真带来革命性变革。基于此,对三维射线跟踪模型原理、技术特征、适用环境及其对地图的要求、对地图结果的影响等方面做了详细论述,并通过CW发射方式及DT实地试验测试对提升结果进行了认真分析对比,还对其引入所带来的有关问题进行了详细分析。     

通信基站电磁辐射场强的系统建模与数值仿真

基于数字城市管理和射线跟踪算法的基本原理,采用三维实体环境建模、反向射线跟踪路径搜索和辐射场源射线多途径传播的场强合成算法,建立了一种对城市小区移动通信基站附近的电磁辐射场强进行系统建模与数值仿真的新方法.该方法有效克服了传统电波传播预测模型不能适应不同小区环境下的复杂建筑模型以及其他确定性方法不能精确找到电波传播路径的局限性.在城市小区的不同空间分布区域,本算法的计算机软件数值仿真结果与实地测量结果的良好一致性验证了该方法的实用性、有效性和正确性.     

四旋翼无人机的轨迹规划跟踪控制研究

针对四旋翼无人机的实际应用需求，开展轨迹跟踪控制研究。提出了一种基于快速扩展随机树（RRT）算法的Dubins航迹规划方法，同时搭建了四旋翼模型，并设计了轨迹跟踪控制方案对所提出的规划路径进行了轨迹跟踪仿真。该RRT-Dubins算法采用RRT算法对有障碍区域的无人机路径进行有效规划，然后利用Dubins路径对规划出的轨迹进行平滑处理，以形成一条无人机可飞行路径。仿真实验表明，采用所提出的轨迹规划方法及路径可以较好地规避障碍区域，且轨迹平滑更适合无人机飞行，同时验证了所提轨迹跟踪控制方案的有效性。     

基于Crosswave射线追踪模型的TD-LTE规划仿真

首先介绍无线电波的传播特性以及传播模型的分类;然后对Crosswave射线追踪模型进行详细分析;最后结合某区域的TD-LTE网络规划仿真案例,论证Crosswave射线追踪模型在TD-LTE网络规划中的可行性和准确性。     

射线跟踪模型在WCDMA无线网络规划中的应用分析

文章分析了三种常用的射线跟踪模型的特点和适用场景。通过WCDMA无线网规的实例，分别以覆盖空洞、导频污染、弱覆盖和越区覆盖等问题区域的优化为例，采用Volcano三维射线跟踪模型进行仿真优化及调整，并给出了相关分析。     

射线追踪模型在无线城市网络规划中的应用

为满足无线城市数据业务需求而导致无线网络密度的增加,以及由于城市中基站周边高层建筑较多,使得传统传播模型在规划仿真中偏差较大而仿真的准确程度影响着整个规划过程的准确性和合理性的验证。本文介绍采用射线追踪模型解决城市无线网络规划中仿真精度的难题,并使用特定射线追踪模型分析其在无线城市网络规划中的应用。     

基于三维的射线跟踪八叉树算法的城市微区电波传播预测算法模型

本文建立了一种有效的基于射线跟踪技术的三维城市微区电波传播预测的计算模型.该模型将计算机图形学中的八叉树分区技术扩展至射线跟踪技术,并由此提出了一种新的有效的射线跟踪算法,射线跟踪八叉树算法.并基于几何光学、一致性绕射(UTD)对场强进行计算,所得结果与实测值及FDTD的结果进行了比较.     

A ray-tracing approach for indoor/outdoor propagation throughwindow structures

A ray-tracing approach for indoor/outdoor propagation through windows is proposed. Using both the finite-difference time-domain (FDTD) method and a ray-tracing algorithm, several cases of indoor/outdoor propagation through windows were investigated. It is shown that wave transmission through windows cannot generally be accounted for through a single transmission coefficient parameter. Instead, a full diffraction pattern needs to be accounted for and multiple-ray representation is therefore required. It is also shown that a single window model may be used to calculate transmission through set of windows in a typical building structure as a building block. Results from the implementation of a multiple-ray representation and FDTD simulations showed good agreement. Results were validated for both normal and oblique incident cases. The developed ray-tracing approach, therefore, facilitates the use of the developed window model in available ray-tracing algorithms often used for propagation characterization of urban environments. Simulation results were further validated by conducting measurements on scaled models at 30 GHz. The experimental results agreed well with the simulation data, thus validating the accuracy of the developed ray-tracing model for transmission through windows     

面向密集城区网络的覆盖预测模型的应用研究

在目前密集城区CDMA无线网络日趋复杂的情况下,如何使覆盖预测与网络实际充分拟合,发挥射频仿真工具在网络优化中的作用,是一个十分值得探讨的课题。本文从密集城区的CDMA无线网络入手,分别选取了统计型模型的Okumura-Hata模型和确定性模型的3D射线跟踪模型进行研究,分析了两种模型在密集城区场景下的差异,最终在实践的基础上提出了面向密集城区的覆盖预测模型的选取方案。     

Efficient ray-tracing methods for propagation prediction for indoorwireless communications

The application of several ray-tracing techniques, in combination with the uniform theory of diffraction, is presented for efficient prediction of propagation in the UHF (communication) band in an indoor environment. First, we improve the computational efficiency of the two-dimensional (2D) ray-tracing method by reorganizing the objects in an indoor environment into irregular cells. Second, by making use of the two-dimensional ray-tracing results, a new three-dimensional (3D) propagation-prediction model is developed, which can save 99% of the computation time of a traditional three-dimensional model. This new hybrid model is more accurate than two-dimensional models, and more efficient in computing the path loss to any point in the building than traditional three-dimensional models. In this model, reflection and refraction by layered materials, and diffraction for the corners of the walls, are considered. A patched-wall model is used to improve the accuracy of prediction in the method. Finally, a comparison between simulation and measurements shows good agreement     

Spatio-temporal channel characterization in a suburban nonline-of-sight microcellular environment

This paper reports a spatio-temporal channel characterization of a suburban non-line-of-sight microcellular environment in which azimuth-delay profiles obtained by an experiment are compared with ray-tracing simulation. The results are statistically treated step by step to extract model parameters in order to characterize the spatio-temporal channel. The experimental results we obtain are used to improve the accuracy of the simulation process. We are able to obtain a very good agreement between the simulation and the experiment, with the exception of the exponential decay of the delay profile. The results presented can be directly used to implement the stochastic spatio-temporal channel model, based on the deterministic ray-tracing simulations     

A ray-tracing method for modeling indoor wave propagation andpenetration

A ray-tracing method for waves inside buildings is presented. Ray tubes are used to model the wave propagation and penetration and all the significantly reflected and transmitted ray tubes from interfaces are included. Also, the cross sections of the ray tubes at the field points are evaluated to find the spreading factors of the waves and then the geometrical optics (GO) contributions at the locations of the receiving antenna. A program has been developed according to this ray-tracing technique that can be applied to simulate waves transmitted through and reflected from electrically large complex 2D and 3D bodies. To verify this ray-tracing program, 2D moment method (MM) solutions for wave propagating in a two-room structure and also through a stair-shaped wall above a lossy ground are used to compare with those obtained from the ray tracing. Besides, comparisons of field measurements and ray-tracing simulations at 900 and 1800 MHz performed in a corridor on different floors and inside a staircase are shown. The effective complex dielectric constants of the buildings determined from a free-space method are employed in the simulations and a vector network analyzer is used for the field measurements. Good agreements are obtained. In addition, measured results for waves penetrating an exterior wall with metal-framed windows at 1290 MHz are employed to test the ray-tracing solutions, which indicate that scattering from the metal frames may be significant for field points near the windows. This ray-tracing program can be applied to evaluate the channel characteristics for the indoor wireless communications     

Indoor MIMO Channel Modeling by Rigorous GO/UTD-Based Ray Tracing

This paper presents a multiple-input-multiple- output (MIMO) channel model based on rigorous ray-tracing techniques, which is based on a full 3-D implementation of geometric optics and the uniform theory of diffraction (3-D GO/ UTD). Results obtained from measurements and simulations of the correlation matrix and capacity of a 2 times 2 MIMO system in specific indoor environments at a frequency of 2 GHz are presented. The channel capacity has been calculated for the different local areas considered in open- and office-area scenarios, starting from the measurements carried out there, as well as from the ray-tracing simulated channels. The rigorous and quantitative comparison between measurements and simulations shows that the model accuracy is sufficient for the analysis and design of the different aspects of the full MIMO system. The results from the ray-tracing model can also be used to extract general statistical characteristics and parameterize statistical models for different types of environments, without the need to carry out large and costly measurement campaigns. In addition, the measured data are used to study the impact of the channel on the achievable capacity of a 2 times 2 MIMO system in typical indoor scenarios at 2 GHz.     

Measurements on scaled models of urban environments and comparisonswith ray-tracing propagation simulation

Scaled models of simple two-dimensional (2-D) urban environments are considered in order to investigate propagation along a vertical plane. Specifically, path loss measurements are taken for different positions of the transmitting and receiving antennas at 25 GHz. Then measurement results are compared with theoretical predictions computed by a ray-tracing polygonal line simulator. The measurements indicate a very good agreement between the ray-tracing model and the experiments     

基于射线追踪法的移动通信信道建模分析

移动通信信道的研究一直是通信系统的难点,传统上的研究方法都有很明显的缺陷,而近年来,随着射线追踪法的发展,运用射线追踪法研究移动通信信道成为现实,而且基于射线追踪法的移动通信信道建模分析方法相对传统方法也具有很多优势。运用射线追踪法,建立了城市环境下移动通信信道的射线追踪模型,并对其性能进行了仿真分析。