Total CNIDR degradation during rain fade conditions of a dual polarized satellite link suffering from double adjacent satellite interference

Atmospheric impairments have a significant influence on the performance of modern satellite communication networks, working at Ku, Ka and potentially Q/V frequency bands. Both differential rain attenuation from an adjacent satellite system, operating at the same frequency range, and cross‐polarization phenomena on dual polarized satellite systems due to rain and ice crystals, induce a further aggravation on the already limited signal‐to‐noise‐plus‐total‐interference ratio (CNIDR), due to the frequency and orbital congestion of today's global communication satellite constellation. In the present paper, a new statistical methodology, towards the modelling of CNIDR under rain fade conditions, is proposed to include interference effects by two adjacent satellites, incorporating the impact of correlated fading channels (spatial rainfall inhomogeneity) of multiple slant paths. The method is based on a convective raincell model and the lognormal assumption for both the point rain‐rate statistics and the slant‐path rain attenuation. The obtained numerical results indicate the significant impact of the second interfering satellite on the aggravation of total interference effects. Some simple mathematical formulas for the prediction of the CNIDR, based on the derived theoretical results, and demonstrating the influence of various link parameters on the total link availability statistics, are also presented. Copyright © 2009 John Wiley & Sons, Ltd.     

Adjacent Satellite Interference Effects on the Outage Performance of a Dual Polarized Triple Site Diversity Scheme

The design of reliable, modern satellite communication networks, in which both frequency and orbital congestion are increasing, requires modeling of interference effects. The dominant sources of aggravation of nominal interference due to propagation phenomena are assumed to be differential rain attenuation from an adjacent satellite communication network operating at the same frequency and cross polarization due to rain and ice-crystals. A physical methodology to predict the statistics of the carrier-to-noise-plus-total-interference (CNIDR), which has already been applied to single and double-site systems, is extended to include triple-site diversity reception schemes. This method is based on a model of convective raincells model and the lognormal assumption for both the point rainfall statistics and slant path rain attenuation. The statistical properties of spatial inhomogeneity of rain attenuation over six satellite slant paths is firstly here presented. A set of simple, approximate formulas are presented which follow from a regression analysis on the previous theoretical results. The results serve to examine the influence of various parameters upon the total availability performance.     

Rainfall propagation impairments for medium elevation angle satellite‐to‐earth 12 GHz in the tropics

Rain attenuation is the dominant propagation impairment for satellite communication systems operating at frequencies above about 10 GHz. The rainfall path attenuation at 12.255 GHz measured at Universiti Sains Malaysia (USM) for 4 years (2 January to 5 December) is presented. This paper presents an empirical analysis of rain rate and rain attenuation cumulative distribution functions obtained using 1‐min integrated rainfall data and comparison of the measured data with data obtained from well‐established rain model attenuation predictions. Copyright © 2008 John Wiley & Sons, Ltd.     

A model for the estimation of the carrier‐to‐noise plus total interference ratio between two adjacent dual polarized satellite links sharing the same frequency band

In modern satellite communications, matters such as frequency congestion, transmission of dual polarized carriers and increase of the number of geostationary satellites in use, necessitate the implementation of interference analysis in neighbouring networks so as to ensure satisfactory quality of service. In this paper, a recently proposed model for the prediction of the degradation of the carrier‐to‐interference ratio due to differential rain attenuation and cross‐polarization, which is applicable only for the noise‐dominant case, has been properly modified to include the general case. The proposed model is based on the lognormal assumption for the point rainfall rate statistics and the convective raincell model. Due to complexity of the proposed analysis, some simple regression‐derived formulas have been generated forming a very useful tool for the system engineer. The elaborations of numerical results examine the influence of various parameters upon the total availability performance and the optimum utilization of the geostationary orbit. Copyright © 2005 John Wiley & Sons, Ltd.     

Microwave depolarization versus rain attenuation on earth space in Malaysia

The wave propagation experiments using Japanese geostationary satellite Superbird‐C have been performed at the Universiti Sains Malaysia earth station. A relationship between rain depolarization and attenuation, valid for earth‐space path at microwave wavelengths, is presented. Cumulative rain attenuation and cross‐polarization discrimination (XPD) statistics are given for the period of 4 years (2002–2005) at 12.255 GHz. XPD varied from 44 dB at 1% to 16 dB at 0.001% of time the abscissa is exceeded. Comparisons were made with available data sets and with five simple XPD models and the results indicate a good performance by the simple isolation model and the CHU model compared with the others. These results serve as checks on the theoretical models needed for predicting communication system performance in geographical regions especially for equatorial climate where measurements are not available. Copyright © 2008 John Wiley & Sons, Ltd.     

Experimental assessment of slant‐path rain attenuation variability in the Ka‐band

This study is based on the results of a slant‐path Ka‐band propagation experiment carried out in Madrid, Spain, regarding rain attenuation, which is the main propagation impairment in this frequency band. The experimental and statistical results correspond to seven complete years of measurements, a period large enough to accomplish a comprehensive analysis in order to characterize the variability of rain rate and attenuation. It is shown that year‐to‐year variability is significant in temperate climates as Madrid's. The aforementioned significance is also apparent with regards to seasonal, monthly, worst‐month and hourly variability concerning rain attenuation, which are also discussed and related when possible to the variability of the rain phenomena, either represented by the total amounts of rainfall in the different periods or by rain rate statistics. Copyright © 2015 John Wiley & Sons, Ltd.     

Prediction model of time diversity using Japan rain radar data

The effects of rain attenuation on communication systems will become more pronounced in future satellite communication systems, especially with the planned use of the 21‐GHz band or higher‐frequency bands. Diversity techniques provide a solution to mitigate rain attenuation effects. This study proposes a time diversity technique, one such technique that is likely to demonstrate high effectiveness. To model the system, rainfall rate statistics are necessary, and reliability is improved as the amount of statistical data increases. This paper derives the cumulative distribution of the rainfall rate across Japan over 4 years using rain radar data from the automated meteorological data acquisition system and ground‐based rain radar network and evaluates the rainfall rate at 23 observation points across Japan. We carry out a performance evaluation for all locations within Japan to confirm the efficiency of the time diversity method. Finally, we propose prediction model of the time diversity gain for Japan and other significant parameter which is time correlation of rainfall rate that was found from the time diversity results for further investigation. Copyright © 2016 John Wiley & Sons, Ltd.     

Interference Studies Between Adjacent Satellite Communications Systems operating Above 10 GHz and Using Power Control as Fade Mitigation Technique

Interference problems are arising from the spectral coexistence between satellite communication networks that operate at frequencies above 10 GHz and particularly when they employ power control as fade mitigation technique. This situation is aggravated due to tropospheric propagation phenomena. In this frequency range, rain attenuation is considered to be the dominant tropospheric fading mechanism. The conditional acceptable intersystem interference probability of the Carrier-to-Interference Ratio of a satellite terminal interfered by an adjacent satellite network is defined as a figure of merit and analytically calculated taking into account a physical-mathematical model for the rainfall medium. The correlated propagation fading phenomena over multiple slant paths are accurately incorporated. The proposed model is flexible and can be applied on a global scale since it incorporates the local climatic conditions concerning the point rainfall rate and the spatial rainfall inhomogeneity. Useful numerical results of the proposed model are obtained and the impact of various crucial operational and geometrical parameters of satellite networks’ coexistence is examined. The numerical results have been also verified through simulations using a multi-dimensional rain attenuation synthesizer. Finally, simple and easy-calculated formulas for the satellite communication designers for back of the envelope computations are given.     

Inter‐annual variability,risk and confidence intervals associated with propagation statistics. Part I: theory of estimation

This set of two companion papers aims at providing a statistical framework to quantify the inter‐annual variability observed on the statistics of rain attenuation or rainfall rate derived from Earth‐space propagation measurements. This part I is more specifically devoted to the theoretical study of the variance of estimation of empirical complementary cumulative distribution functions (ECCDFs) derived from Earth‐space rain attenuation or rainfall rate time series. To focus the analysis on the statistical variability but without loss of generality, synthetic rain attenuation time series are considered. A large variability on the ECCDFs, which depends on the duration of the synthetic data, is first put into evidence. The variance of estimation is then derived from the properties of the statistical estimator. The formulation is validated numerically, by comparison with the ECCDF variances derived from the synthetic data. The variance of the fluctuations around the CCDF is then shown to be dependent on the average of the correlation function of the time series, on the probability level and on the measurement duration. This variance of estimation is needed as a prerequisite in conjunction with the knowledge of the climatic variability to characterize the yearly fluctuations of propagation statistics computed from experimental time series. The extensions from simulations to experiments as well as the application to system planning are detailed in part II. Copyright © 2013 John Wiley & Sons, Ltd.     

地空路径统计雨衰减建模的几个问题

地空路径雨衰减统计特性是卫星通信等地空无线电系统设计和运行评估的关键参数.针对地空路径统计雨衰减的建模研究, 分析了影响模型准确度的几个关键因素, 它们包括雨滴谱分布、雨顶高度、降雨率在水平和垂直路径的不均匀性等.同时比较分析了现有主要模型计算的路径调整因子随仰角的变化、与频率的关系等, 讨论了现有模型的局限性和可能的改进途径.通过上述对比研究, 提出了地空路径雨衰减统计建模向确定性模型方向发展的观点.     

Rain Attenuation Ratios on Short Microwave and Millimeter Wave Bands Earth-Space Paths

The knowledge of the ratio of rain attenuation at one frequency to that at another on slant paths is useful for the design of satellite-to-Earth communication links and up-link power control systems. It is well known that the rain attenuation is influenced by parameters of precipitation along the slant path such as DSD (raindrop size distribution), raindrop temperature, rainfall rate, and so on. In this paper, based on several DSDs applied to various climate zones, at short microwave and long millimeter wave bands, the attenuation ratios are estimated on Earth-space paths. A comparison of the prediction results with the experiment data in Boston and Kashima areas is carried out. It is shown that the M-P and Weibull DSD applied to rain attenuation ratios estimation are better DSD at higher latitude regions. The Guangzhou DSD applied to rain attenuation ratios prediction is better in tropical and subtropical areas in China. The lognormal DSD may be a appropriate DSD applied to predict rain attenuation ratios in tropical areas at A_down>1dB or R>15mm/h. However, the attenuation ratios predicted by the Guangzhou DSD disagree with by the lognormal DSD, it requires that the DSD applied to predict rain attenuation ratios are further studied in tropical areas.     

Microwave link dual-wavelength measurements of path-averageattenuation for the estimation of drop size distributions and rainfall

Microwave attenuation measurements at 25 and 38 GHz made on a 2.3-km microwave link are employed to estimate drop size distributions (DSD), rainfall rate, and rainfall accumulation. A theoretical model for the propagation of microwaves in a link system sets forth the basis for the development of a dual-wavelength analytical technique to invert two parameters of a path-average gamma DSD. The DSDs obtained from the technique are evaluated in conjunction with point measurements performed with a 2-D video disdrometer. Additionally, the DSDs yield path-average rainfall rates and rainfall accumulation which are compared with path-average measurements from a network of optical and tipping bucket rain gauges located beneath the link path, and with estimates based on empirical power law relations     

A comparison of copolar and cochannel satellite interference prediction models with experimental results at 11.6 and 20 GHz

One of the main propagation effects on interference between adjacent Earth–space paths is the differential rain attenuation. In the present paper, two existing copolar and cochannel satellite interference prediction models are compared with experimental data of this kind, derived from radar or attenuation measurements. The comparison shows a quite satisfactory agreement and this combined with the fact that the data refer to satellites quite displaced in the geostationary orbit leads to the following conclusion: the predictive models under consideration can be used not only for fixed satellite systems but also for mobile systems using general antennas with low gains. Copyright © 2000 John Wiley & Sons, Ltd.     

Centimeter wave propagation experiments using the beacon signals of CS and BSE satellites

The wave propagation experiments using Japanese geostationary satellites CS (20/30 GHz) and BSE (12/14 GHz) satellites have been performed at the Kashima earth station of the Radio Research Laboratories (RRL). Cumulative rain attenuation and cross-polarization discrimination (XPD) statistics are given for the period of three years at 11.7 GHz (vertical polarization) and for the period of four years at 19.5 GHz (circular polarization). It is shown that the yearly rainfall rate and attenuation distributions are well approximated by log-normal distributions, and the XPD distribution is well approximated by a normal distribution. Monthly and time-of-day variation of the attenuation and XPD distributions are presented. Duration statistics of attenuation and XPD are presented and characterized. Other characteristics in the wave propagation, such as effective path length, frequency dependence of attenuation, and joint statistics of attenuation and XPD are derived and discussed. Rainfall events are classified into three rainfall types, "stratus," "cumulus," and "others" using measurements of the radar reflectivity factor along the satellite-to-earth path, and the dependence of XPD characteristics on the rainfall type is also presented and discussed. Some prediction methods of calculating attenuation and XPD statistics are applied to the data obtained in these experiments and the predicted results are compared with the measured ones. It is found that some corrections are needed when the XPD statistics are predicted from the attenuation statistics using the theoretical relation between XPD and attenuation.     

Ka卫星通信系统中雨衰分析

简单介绍了雨衰的机理,并以我国原邮电部给出的雨衰模型为基础,根据我国10个主要城市的降雨数据和地理位置参数,计算出轨道位置在80°E的通信卫星在上行水平极化/下行垂直线极化的情况下,Ka波段(30/20GHz)的雨衰A0.01,并就雨衰对下行卫星链路G/T值恶化带来的影响进行了分析讨论,给出了相应的计算方法,最后总结了几种抗雨衰措施。     

Ice crystals and raindrop canting angle effects applied to satellite interference prediction with respect to heavy rain climatic zones

For frequencies above 10GHz the performance of the operating satellite systems is mainly aggravated because of the potential existing severe rain attenuation. As a result of the above fading mechanism, the dominant interference sources encountered in this frequency band are the following: differential rain attenuation induced by an adjacent satellite system operating in the same frequency, and cross talk between orthogonally polarized signals. The latter source concerns of course satellite systems employing the dual polarization mode. In the present paper, an already existing method to predict interference statistics, due to above reasons, is properly modified to include ice crystals and raindrop canting angle effects. The assumption that the point rainfall rate statistics follows a gamma form, valid for heavy rain climatic regions such as J, M, N, P, Q zones, is also adopted. The sensitivity of various parameters affecting the interference performance, after introducing the novel assumptions, is finally investigated.     

On the rain attenuation dynamics: spatial‐temporal analysis of rainfall rate and fade duration statistics

Knowledge about the dynamic characteristics of rain attenuation is of utmost importance for many applications in terrestrial and satellite communication systems operating at frequencies above 10 GHz. Long‐term rain rate statistics and rain rate duration statistics are usually available from meteorological data. In this paper, a spatial–temporal analysis is employed in order to evaluate the rain attenuation power spectrum of a terrestrial/satellite path. The predicted power spectrum is compared with experimental data. Based on the spectral analysis of rainfall rate a method for converting rain rate duration statistics to link fade duration statistics is also proposed. Fade duration statistics are presented for terrestrial and satellite links and compared with available experimental data. The agreement between the predicted results and the experimental data has been found to be quite encouraging. Finally, numerical results are presented for various climatic zones, elevation angles and frequencies. Some very useful conclusions concerning the dynamic properties of rain attenuation for a microwave path are deduced. Copyright © 2003 John Wiley & Sons, Ltd.     

Cross polarization on line-of-sight links in a tropical location:effects of the variation in canting angle and rain dropsizedistributions

The effects of the variation in canting angle of falling raindrops and the distribution of raindrop sizes in different types of rain on cross polarization discrimination (XPD) on line-of-sight propagation paths in a tropical location in the frequency range 1-50 GHz are investigated. The dropsize distribution (DSD) model of Adimula and Ajayi (see Ann. Telecomm., vol.51, no.1/2, p.87-93, 1996) has been used. Although, some previous studies of XPD assumed equi-orientation of the raindrops along the propagation paths, the present study employs the more realistic distribution of canting angles along the path. The results obtained show that the XPD improves by about 4-7 dB over those based on the equi-orientation model. It is also shown that for the same copolar fade and for frequencies greater than about 10 GHz, the variation of the XPD with copolar attenuation (CPA) is relatively insensitive to the assumed DSD in rain and that the deterioration in signal quality or outage will be influenced more by the signal attenuation rather than by the cross-polarization interference     

中国Ku波段广播通信卫星雨衰减分布

雨衰减对于１０ＧＨｚ以上无线电系统的影响是极为严重的。本文根据我国６５个站点的分钟降雨率数据，利用ＩＴＵ－Ｒ最新给出的雨衰减预报模式，计算出我国未来１２ＧＨｚ三个轨道