A New Formula of Specific Rain Attenuation for Use in Prediction Methods

A new formula of specific rain attenuation aR ^b has been studied, the analytic expressions for a and b are regressed as function of operating frequency and polarization of microwave and millimeter wave system, which are based on the values given by International Telecommunication Union-Radio communication. The results of a and b calculated by this formula are in good agreement with that of tabulated by ITU-R for the power-law relationship of specific attenuation for rain for use in prediction methods.     

Analytic Specific Attenuation Model for Rain for Use in Prediction Methods

Based on the values of k and α given by ITU-R for the power-law relationship of specific rain attenuation γ _R=kR ^α, the analytic expressions for k and α are regressed as a function of frequency and are in high agreement with the values tabulated. The specific rain attenuation calculated by the analytic expressions are also in high agreement with those by the values of k and α tabulated. Comparisons with other analytic expressions show that the ones in this paper are more accuracy and simple.     

一种改进的Ka频段雨衰减预测模型

论述了Ka频段中雨衰减率和DAH雨衰减预测模型,为了建立适合我国Ka频段的雨衰减预测模型,对DAH雨衰减预测模型进行了改进.以西安和北京地区为例,通过和ITU-R频率比例关系进行仿真比较,结果表明,改进后的模型克服了DAH模型的缺陷,在理论上更适合我国的气候和地形.     

广州地区雨滴尺寸分布模型及雨衰减预报

本文利用广义ｇａｍｍａ分布模型处理分析了１９９２年夏季广州雨滴尺寸分布测量数据，得到了广州地区雨滴尺寸分布模型，并利用这一模型计算了３３．５ＧＨｚ和９３ＧＨｚ雨衰减，其计算值与同期测量结果之间有很好的一致性。     

A Stochastic Dynamic Model of Rain Attenuation

A dynamic mathematical model of rain attenuation has been developed and is presented in this paper. This model permits the expression of analytic relationships between parameters commonly used to describe the properties of interest for communication. The dynamic model is based on the lognormal distribution of rain attenuation and utilizes a memoryless nonlinear device to transform attenuation and rain intensity into a one-dimensional Gaussian stationary Markov process. Hence, only one parameter is required to introduce the dynamic properties of rain attenuation into the model. Experimental results and the known properties of rain have been used to derive and to verify the model; comparative results are presented and demonstrate good correspondence. The application of the model to the statistical analysis of the performance of communications systems is illustrated in the paper. The use of a dynamic rain attenuation model is necessary in order to analyze radio communication systems with transmit power control to offset the effects of rain attenuation, and where the finite response time of the control system affects the performance. An advantage of the model is the simplicity with which it allows simulation of communication link performance under the influence of rain attenuation. Such simulations are of great interest for complex models of adaptive networks where several deteriorating effects, including finite response times, are present.     

Empirical Rain Attenuation Model for Earth-Satellite Paths

A set of three simple empirical formulas is given for the calculation of long-term rain attenuation distributions on earth-satellite microwave radio paths from long-term (≥20 yr) distributions of 5-min point rain rates. The calculated results agree well with six sets of rain attenuation data on earth-satellite paths measured in Illinois, Georgia and New Jersey. This simple method, which is an extension of that obtained previously by the author for terrestrial radio application, is useful in the engineering of satellite communication systems at frequencies above 10 GHz.     

基于BP网络的卫星通信雨衰预测模型

电磁波的降雨衰减对卫星通信链路具有很大的影响。在分析基于BP算法的多层前馈网络具有逼近任意连续非线性函数的能力和降雨率与降雨衰减的非线性关系的基础上,提出并建立了基于BP神经网络的卫星通信降雨衰减预测模型,根据某地区的实测数据进行训练和预测,并与ITU-R模型进行了对比。结果显示神经网络模型具有较小的误差,为降雨衰减预测提供了一种更加准确有效的方法。     

基于非平稳时序ARIMA模型的W频段雨衰预测

针对目前绝大多数雨衰预测模型仅验证到55 GHz,而经过验证的W频段预测模型相对较少,且存在模型表述复杂度高、计算量大的问题,该文提出一种结构简单、计算量小的实时预测方法。该方法基于ARIMA模型,利用非平稳雨衰时序中相邻时序间的相关性建立预测模型,对初始序列进行平稳性检验,通过差分变换将非平稳序列转化为平稳序列,并对平稳化后的时间序列进行参数估计及诊断检验,将传统非线性预测转化为线性预测。并先将该ARIMA(1,1,6)模型在不同极化方式、预测间隔和时序个数的条件下进行比较,然后分别与ITU-R, Silva Mello模型在垂直极化、预测间隔0.10 GHz,时序个数50的条件下进行比较,最后使用ARIMA(1,1,6)模型进行预测,并对照预测序列与仿真序列的吻合度。结果表明,ARIMA模型与ITU-R, Silva Mello模型所得结果预测误差不超过10-3 ,且衰减变化趋势基本相同,预测序列与仿真序列间吻合度较高,说明该方法可用于W频段雨衰预测,且预测精度高,模型表述简单。     

Statistical Prediction Modeling of Rain Induced Attenuation and Depolarization

Millimeter wave rain co-polarization attenuation, CPA, and cross polarization discrimination, XPD, measurements have been made at 35GHz and 94GHz over a line-of-sight link. On the basis of these experimental results, a study of this rain medium has been made with the method of link measurements. In this paper, we presented a statistical prediction modeling of rain-induced attenuation and depolarization from the statistical distribution of the rain intensity, and the size, and canting angle of raindrops. Our computational results are in good agreement with data of measurements.     

The Prediction of Rain-Induced Attenuation in MM Wave Band by Rain Medium System Model

While the millimeter radio wave propagates through rainfall, it will be attenuated heavily due to assimilation and scattering of rain. It is imperative to establish a simple and effective model to predict the rain-induced attenuation. In this paper, the rainfall is taken as a random system that can attenuate the radio wave. The transfer function matrix model is selected to be the random system model. Using experiment rain attenuation data at different rain rate, the correlation entropy and residue error of the system is obtained by system identification method. On the basis of correlation entropy and residue error, we can determine the order of the predication system. At last, the predication model that can forecast heavy rain attenuation by small rain attenuation is gotten by applying the least square method. The comparison shows that the discrepancy between the predication result of the obtained model and the experiment rain attenuation data is relatively minor.     

由实测小时雨量预报地星通信雨致衰减的方法研究

利用１９９１年中国３３３个地面雨量站的小时雨量数据，进行降雨率累积概率对数正态和伽玛分蝗计算比较，得出伽玛分布在较大的降雨范围内能更好地反映实际降雨率累积概率分布。     

In Search of a Location-Centric Rain Attenuation Model

Wireless Personal Communications - In search of an accurate location-centric rain-induced attenuation model, in this paper, the authors have investigated the measured attenuation and rainfall...     

基于随机微分的雨衰模型

本文利用随机微分理论研究了卫星通信中雨衰的统计特性,首先利用非线性变换得到了雨衰的随机微分方程,然后利用福克尔一普朗克（Fokker-Planck）方程给出了雨衰的概率密度函数,最后利用办6公式推导出了雨衰的功率谱密度函数,并通过实测数据验证了所提方法的准确性。     

基于灰色系统理论的雨衰减短期预报方法研究

雨衰减对10GHz以上频段的无线通信有很大的影响,在使用卫星通信系统时必须采取合理的策略以补偿降雨造成的衰减。为了给星地链路的自适应功率控制技术提供保障,首次将灰色系统理论应用在雨衰减短期预报中,分析给出了选择灰色系统模型和参数的原则。最后选取海口站Ka 频段地空链路的实测数据进行了验证,利用获得的雨衰减数据对未来间隔1s 和5s 的时刻进行预测,结果表明,基于灰色系统的雨衰减预测和实测数据吻合较好。     

General N-State Markov Model for Rain Attenuation Time Series Generation

Nowadays and mainly in the near future the wireless point-to-point or point-to-multipoint connections are operating in high frequency. These systems are applied in feeder network for future cellular mobile communication systems or BFWA (Broadband Fixed Wireless Access) networks. Besides the obvious benefits of the applied high carrier frequency there is a significant disadvantage, the considerable attenuation caused by precipitation, especially by rain. For accurate planning of the proposed microwave links the statistics of the expectable rain attenuation is highly important. Applying our previous research results the this work provides a general N-state Markov Chain model to generate rain attenuation time series on a proposed microwave link according to the link parameters. The first and second order rain attenuation statistics of the generated time series can be derived directly from the Markov model parameters, so the N-state Markov model can be applied for prediction of rain attenuation on the proposed link even in the early planning phase. With our proposed model very accurate realisation of the physical fade process can be achieved.     

The Study of Rain Specific Attenuation for the Prediction of Satellite Propagation in Malaysia

Specific attenuation is the fundamental quantity in the calculation of rain attenuation for terrestrial path and slant paths representing as rain attenuation per unit distance (dB/km). Specific attenuation is an important element in developing the predicted rain attenuation model. This paper deals with the empirical determination of the power law coefficients which allow calculating the specific attenuation in dB/km from the knowledge of the rain rate in mm/h. The main purpose of the paper is to obtain the coefficients of k and α of power law relationship between specific attenuation. Three years (from 1st January 2006 until 31st December 2008) rain gauge and beacon data taken from USM, Nibong Tebal have been used to do the empirical procedure analysis of rain specific attenuation. The data presented are semi-empirical in nature. A year-to-year variation of the coefficients has been indicated and the empirical measured data was compared with ITU-R provided regression coefficient. The result indicated that the USM empirical measured data was significantly vary from ITU-R predicted value. Hence, ITU-R recommendation for regression coefficients of rain specific attenuation is not suitable for predicting rain attenuation at Malaysia.     

Electromagnetic Waves Attenuation due to Rain: A Prediction Model for Terrestrial or L.O.S SHF and EHF Radio Communication Links

Because of the interest raised for SHF and EHF radio communications, the attenuation of electromagnetic waves by rain will always constitute a major concern for telecommunication engineers and scientists. The rain attenuation prediction models exposed in literature calculate the attenuation related to a given rain rate or else to a given percentage of time. The new model proposed in this paper, predicts with a good accuracy the percentage of time for which any given rain attenuation will be exceeded on terrestrial SHF, EHF radiowaves links, provided the rain rate R₀₀₁ (mm/h) that represents rain rate value exceeded for 0.01% of time in the locality of interest is available. R₀₀₁ (mm/h) data being available for most of the localities across the world in ITU-R data base, we may conclude that this new model proposed here, can be broadly and successfully used.     

Proposed Model for Radio Wave Attenuation due to Rain (RWAR)

Radio wave attenuation is primarily caused by the absorption of a radio signals by some atmospheric phenomenon like rain, snow or ice, clouds, dust etc. These losses are more prevalent in the frequency ranges above 10 GHz. Attenuation caused by rain is not only limited to satellite up-link and down-link but it can also affect the point-to-point terrestrial microwave links above 10 GHz. This paper briefly discussed about the work done by researchers at different parts of the world regarding the attenuation caused by the rain for higher frequencies. It then proposes a mathematical model for prediction of radio wave attenuation due to rain. The implementation results of proposed model were also compared with the ITU-R model.

     

An Empirical Model for Prediction of Environmental Attenuation of Millimeter Waves

The latest trends in mobile technology have increased the need for higher spectrum bands from every sector of using wireless applications. As the internet is growing rapidly it has increased the need for wireless services, which require radio spectrum and thus becoming more congested. Engineers show that due to high demand for spectrum, government authorities are regularly introducing schemes to regulate the use of spectrum. New researches are enhancing to resolve the crisis. In order to fix the spectrum for future technologies, propagation studies are required. In this paper an empirical model is proposed for prediction of attenuation due to clouds and fog based on the Rayleigh approximation model. In this model a new concept of calculating dielectric constants of water are also introduced. The implementation results of the proposed model are compared with the other cloud attenuation models. The proposed model proved to be better than the ITU-R model.

     

Rain Attenuation and Doppler Shift Compensation for Satellite Communications

In high‐speed multimedia satellite communication systems, it is essential to provide high‐quality, economical services by using efficient transmission schemes which can overcome channel impairments appearing in the satellite link. This paper introduces techniques to compensate for rain attenuation and the Doppler shift in the satellite communication link. An adaptive transmission technique with a control algorithm to adaptively allocate transmission schemes is used as a countermeasure to rain attenuation. We introduce a new rain attenuation modeling technique for estimating system performance and propose a novel Doppler shift compensation algorithm with reduced hardware complexity. Extensive simulation results show that the proposed algorithm can provide greatly enhanced performance compared to conventional algorithms. Simulation software and hardware which incorporate the proposed techniques are also demonstrated.