Feasibility of neural networks in modelling radio propagation for field strength prediction

A typical back-propagation neural network (BPN) model is developed for modelling radio propagation for field strength prediction based on data measurements of propagation loss (in decibels) with terrain information taken in an urban area (Athens region) in the 900 MHz band. The feasibility of the BPN model is checked against the performance of a conventional semiempirical reference model. The performance of both models is quantified by statistical methods. The evaluation is done by comparing their prediction error statistics of average absolute, standard deviation and root mean square and by comparing their percentage accuracy and correlation of predicted values relative to true data measurements. © 1998 John Wiley & Sons, Ltd.     

914 MHz path loss prediction models for indoor wirelesscommunications in multifloored buildings

Qualitative models are presented that predict the effects of walls, office partitions, floors, and building layout on the path loss at 914 MHz. The site-specific models have been developed based on the number of floors, partitions, and concrete walls between the transmitter and receiver, and provide simple prediction rules which relate signal strength to the log of distance. The standard deviation between measured and predicted path loss is 5.8 dB for the entire data set, and can be as small as 4 dB for specific areas within a building. Average floor attenuation factors, which describe the additional path loss (in decibels) caused by floors between transmitter and receiver, are found for as many as four floors in a typical office building. Path loss contour plots for measured data are presented. In addition, contour plots for the path loss prediction error indicate that the prediction models presented are accurate to within 6 dB for a majority of locations in a building     

蒸发波导模型与微波超视距传播试验对比

海洋蒸发波导是实现近海面超视距电波传播的重要环境,利用蒸发波导模型和电波传播数值算法是获取路径损耗的主要途径.基于海上平台约7个月测量的水文气象参数,对比了Paulus提出的PJ模型和美国海军研究生院(Naval Postgraduate School,NPS)提出的NPS模型,同时利用约1个月的海上超视距传播测试数据...     

基于多层感知器神经网络的路径损耗预测研究

为了更好地服务于5G及未来无线通信系统的网络规划与优化,开展了基于多层感知器(multi-layer perceptron, MLP)神经网络的路径损耗预测研究. 利用有限的地物类型,提出一种表征传播环境的简易方法,避免了繁琐的三维场景建模. 结合测量数据和由环境表征方法提取的环境特征,基于MLP神经网络建立了路径损耗模型. 数据实验的对比分析表明MLP神经网络能够实现路径损耗的准确预测,且环境特征的引入有助于提升模型性能. 为解决干扰地物影响路径损耗模型的准确性以及模型对环境变化的敏感性问题,根据视距(line-of-sight, LoS)和非视距(non-line-of-sight, NLoS)标签改进环境表征方法,进一步提升了模型的稳定性和泛化能力. 所做工作有助于了解无线电波传播特性,为无线网络优化和通信系统设计提供了理论依据.     

区域蒸发波导及微波路径损耗预报与验证

蒸发波导对近海面电磁波传播有重要影响,区域蒸发波导及微波路径损耗预报对评估海上雷达、通信、侦察等电磁系统的性能至关重要. 本文基于美国国家环境预报中心的GFS预报产品和NAVSLaM蒸发波导预测模型,对我国南海海域进行了大面积蒸发波导预报,利用欧洲中期天气预报中心发布的ERA5再分析数据进行了对比,并结合电磁波传播抛物方程模型开展了微波在蒸发波导信道中的路径损耗预报;然后利用在南海北部的路径损耗测试链路,对预报结果的准确性及时效性进行了验证. 再分析数据对比及海上试验验证结果表明,基于GFS数据开展的蒸发波导层中路径损耗预报,除个别异常点外,预报的路径损耗与实测值趋势相同,在前24 h结果与实测值较为吻合,误差在5~10 dB,可以用于大面积蒸发波导层中路径损耗的预报. 另外,试验发现,降雨会导致预报结果与实测数据有很大的误差,在进行电磁波传播计算时,应充分考虑雨衰、海面粗糙等海洋环境.     

800 MHz mobile radio propagation prediction using Kalman filteringtechniques

A method is presented to derive a propagation model to predict the received median signal voltage for an 800-MHz mobile radio system. Results are given of an investigation into the performance of a particular model that was derived using this method. The method uses a Kalman filter that uses propagation measurements to derive a best fit for a particular propagation model to the measured data. The model that was derived is based on propagation measurements made in the State of Florida. The new propagation model uses a plane-Earth propagation model that is corrected with an environmental propagation loss term that takes into account the various environmental effects near the mobile unit. The parameters in the environmental propagation loss model were determined using a Kalman filter that computes minimum mean square estimates of the parameters using measured propagation data. The environmental propagation loss term accounts for the effects of Earth diffraction, hills, valleys, urban and suburban areas, bare and grass-covered ground, bushes, trees, swamps, and propagation over fresh and salt water. It was found that, with the 800-MHz propagation model derived with this method, the prediction error for the received median signal voltage had a standard deviation of 5.08 dB     

基于机器学习和卫星图像的路径损耗预测

基于反向传播神经网络（back propagation neural network,BPNN）构建了一种路径损耗预测模型.通过卫星图像的红、绿、蓝（red, green and blue,RGB）通道的颜色信息来表征无线通信电波传播路径的环境特征,结合路测点与基站的距离特征构建数据集,迭代训练网络参数,以预测传播路径损耗.结果表明,对跨基站路测点的预测结果与实测数据之间的相关系数达到0.83,绝对平均误差控制在0.66 dB,标准差控制在6.65 dB,说明在缺乏某一场景的详细模型和材质参数时,本文模型也能可靠预测无线通信电波的传播路径损耗.此外,本文信道模型与传统信道建模方法多方面的对比与分析表明,本文模型在相同计算资源下可以提供和传统信道建模方法相差很小的预测结果,同时大大缩短预测所需的时间,说明本文模型对传播路径损耗做出快速预测的能力可以用于无线通信网络系统的优化.     

Prediction of Battery Behavior Subject to High-Rate Partial State of Charge

An online optimization procedure provides the parameters of a nonlinear battery model by taking into account a few minutes of measured current–voltage data. Within a defined range in terms of charge current, state of charge (SOC), and duration of charge and discharge events, the model is able to capture the relevant battery dynamics and predict the behavior for the next few minutes. From the battery behavior during specific events, the state of the battery can be revealed, which is defined as the state of function. Validation, which is carried out on measured current–voltage profiles, shows the accuracy of prediction during the high-rate partial SOC operation. Even with the data measured during a city drive within a microhybrid electrical vehicle, the method is able to predict the voltage level during high-rate discharge pulses (cranking).      

Effect of obstacles on VHF TV signal propagation

Field strength data from 13 single-knife-edge diffraction propagation paths were collected over the Indian subcontinent. The suitability of different prediction methods is compared. It is concluded that in urban regions, urban loss should be added to the predicted path loss to explain the observed loss, whereas in the rural/semiurban areas, Epstein-Peterson, Deygout, and CCIR methods predict path losses, which are in close agreement with the observed values     

Measurements and models for radio path loss and penetration loss inand around homes and trees at 5.85 GHz

This paper contains measured data and empirical models for 5.85-GHz radio propagation path loss in and around residential areas for the newly allocated U.S. National Information Infrastructure (NII) band. Three homes and two stands of trees were studied for outdoor path loss, tree loss, and house penetration loss in a narrow-band measurement campaign that included 270 local area path loss measurements and over 276000 instantaneous power measurements. Outdoor transmitters at a height of 5.5 m were placed at distances between 30 and 210 m from the homes, to simulate typical neighborhood base stations mounted atop utility poles. All path loss data are presented graphically and coupled with site-specific information. We develop measurement-based path loss models for propagation prediction. The measurements and models may aid the development of futuristic outdoor-to-indoor residential communication systems for wireless Internet access, wireless cable distribution, and wireless local loops     

室内无线电波传播实验研究

基于对数距离损耗模型,实验研究了普通会议室这一典型室内环境的电波传播特性。通过对传播损耗的测量数据的分析,给出了普通会议室环境下的路径损耗因子和相应的阴影衰落标准差,为室内无线通信系统设计提供了依据。     

Estimating position of mobile terminals from path loss measurements with survey data

Estimating the position of mobile terminals is an important problem for cellular networks. A low cost method of locating the mobile terminal is to use measurements of the radio path loss. The distribution of radio path loss is, unfortunately, a non‐linear function of the mobile terminal location. The non‐linearity results from large obstacles to radio‐wave propagation such as buildings or hills. This paper demonstrates how the conditional density of the location given measured path loss can be approximated as a sum of kernel density functions based on radio propagation data collected from propagation surveys or estimated from computer models. Using these approximate density functions an accurate location estimate of a mobile terminal can be estimated from measured path loss values contaminated by measurement noise. Copyright © 2002 John Wiley & Sons, Ltd.     

蒸发波导微波超视距信道衰落特性研究

针对利用海上蒸发波导效应的微波超视距通信,在三条不同距离跨海电路上开展了外场试验。基于测试数据,统计L、S、C和X频段超视距信道的衰落幅度、深度和速率,对比分析了蒸发波导和对流层散射信道的快衰落特性。并根据大气波导和对流层散射传播预测模型,统计比较了实测和模型预测路径传播损耗。结果表明与对流层散射信道相比,蒸发波导信道衰落幅度、衰落深度和衰落速率均较小,传播预测模型可有效的预测蒸发波导的慢衰落特性。     

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。     

C波段蒸发波导传播衰落特征的试验研究

海洋蒸发波导是海上超视距传播的主要机制，对于海上无线电系统的设计和运行具有重要影响.利用在我国南海开展的蒸发波导环境下的C波段微波超视距传播试验数据，对比分析了不同传播距离下的路径损耗和信号快衰落分布特征.试验结果表明:随着传播距离的增大，路径损耗逐渐接近对流层散射传播损耗，主要传播机制也逐渐从蒸发波导传播向对流层散射传播过渡；5 min采样的接收信号电平快衰落分布接近为广义瑞利分布，衰落深度和衰落幅度均小于瑞利分布.所得结果对利用蒸发波导的通信系统设计具有参考价值.     

Basic transmission loss and delay spread measurements for frequencies between 430 and 5750 MHz

Impulse response radiowave propagation measurements from an urban area of Denver, CO, are described. The basic transmission loss and delay spread are used to characterize the mobile communications environment. These metrics are quantified using path loss slope and delay spread statistics. By analyzing the results versus carrier frequency, the relative propagation impairments at 430, 1350, 2260, and 5750 MHz are compared. It was found that the path loss slope increased on average by 11 dB/dec and the median delay spread decreased from 0.7 to 0.3 /spl mu/s over the decade of frequencies measured.     

Frequency diversity effects of evaporation duct propagation

A comparison of 3, 9.6, and 18-GHz low-altitude over-the-horizon propagation (as influenced by the evaporation duct) is presented. Theoretical and experimental results are given for a 35-km over-water path, where the transmitters were located about 5 m above mean sea level and the receivers were located either 4-5 m or 18-19 m above sea level. Results are presented in terms of the one-way propagation factor in decibels at each frequency. Long-term cumulative frequency distributions of calculated and observed propagation factors are presented. Particular attention is given to the relative performance of each radio frequency to investigate frequency-diversity improvements that may be available on such paths. In most cases presented, there is a close agreement between theory and observations. It is concluded that substantial improvements in received signal levels are likely to be achieved in most areas of the world by a suitable choice of two frequencies in the 10-20-GHz range     

Single knife edge diffraction propagation studies over a hillyterrain

Field strength measurements are made to study the single knife edge diffraction propagation in the hilly terrain of Tirupati, southern India. TV signals originating from Narayana Giri Hill in the VHF band are monitored at 4 different locations of Tirupati for this purpose. The observed values are converted into path loss values and are compared with prediction techniques. An attempt is made to study the adaptability of these techniques and it was found that the ITU-R, Epstein-Peterson (1953), Deygout (1966) and Edward-Durkins (1969) methods are in closer agreement with the observed path loss where as Blomquist-Ladell (1974) over estimates the observed path loss