Analysis of 11 GHz slant path fade duration and fade slope

The letter presents results of an analysis of fade slope and fade duration data collected at 11 GHz within the framework of the OTS propagation experiments in Europe. Evidence is given of the fact that on a statistical basis, fade slope and fade duration are related. This could possibly be used in uplink power control systems.     

Effects of filtering on statistics of rain-induced fade durations

Time series of rain attenuation on a slant path at 11.6 GHz are analysed with two digital filters to show how they affect the statistics of fade durations. It is found that their influence is strong for the usual process considered in literature and it is shown how to take care of such effects. It also discusses a definition of the process which is much less sensitive to filtering. The first process provides data to plan telecommunications satellites with a common onboard resource, and the latter is useful for the distinction between quality and reliability criteria.     

Prediction of slant path rain propagation statistics usingdual-polarized radar

The authors conducted a year-long experiment in which a dual-polarized S-band radar probed the volume surrounding two 11.45-GHz satellite downlink paths during rain. Accuracy was assessed by comparison to directly measured link attenuation with two 11-GHz beacon receivers 7.3-km apart at an 18.5° elevation angle, one colocated with the radar. Drop size distributions calculated from the radar horizontal reflectivity (Z_H) and differential reflectivity (ZDR) measurements were used to predict 11.45-GHz satellite beacon attenuations. The radar-predicted attenuations and those measured on the radio links agree, both on an event basis and in terms of annual cumulative distributions     

Crossing rates and fade durations for diversity-combining schemes over ?-? fading channels

This paper derives exact expressions for the level crossing rate and average fade duration of multibranch pure-selection, equal-gain, and maximal-ratio combiners operating over independent non-identical alpha-mu (also called generalized Gamma or Stacy) fading channels. The derived expressions are in closed form for pure-selection combining and in integral form for equal-gain and maximal-ratio combining. For the two latter schemes, accurate closed-form approximations are then provided. The analytical results are validated by reducing the general expressions to known particular cases and, more generally, by means of simulation. Numerical examples are also given to illustrate the high accuracy of the proposed closed-form approximations.     

Rain rate statistics and fade distributions at 20 and 30 GHzderived from a network of rain gauges in the mid-Atlantic coast over afive year period

The authors examine five years of rain rate and modeled slant path attenuation distributions at 20 and 30 GHz derived from a network of ten tipping bucket rain gauges located on the mid-Atlantic coast of the US in the vicinity of Wallops Island, VA. Distributions are derived from the variable integration time data from 1-min averages or rain rate time series. It is demonstrated that for realistic fade margins at 20 GHz and above, the variable integration time results are adequate to estimate slant path attenuations using models which require 1-min averages. An accurate empirical formula is developed to convert the variable integration time rain rates to 1-min averages. Rain rate and fade distributions corresponding to the overall network average, yearly network average, and site distributions averaged over the five-year period are derived. Significant differences in the distributions are noted for the year-to-year (temporal variability) and the worst year site-to-site (spatial variability) cases     

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.     

Three‐year fade and inter‐fade duration statistics from the Q‐band Alphasat propagation experiment in Madrid

Propagation campaigns are carried out at different frequencies and geographical areas to characterize the slant‐path propagation channel. One of the objectives of the Alphasat Propagation Experiment is to evaluate the performance of satellite links that operate in the Q/V band. Since March 2014, the copolar level of the Alphasat Q‐band beacon signal has been measured at Universidad Politécnica de Madrid, Spain. The fade dynamics—fade and inter‐fade durations—results for three complete years (March 2014 to February 2017) of measurements are presented in this paper. Moreover, the experimental setup and receiver characteristics are described in detail. The collected data (with a mean availability of 97%) can be used to evaluate the atmospheric propagation impairments with a very good degree of accuracy. The probability of occurrence and the fraction of time of fade duration for an average‐year have been compared with the ITU‐R and CRC models with moderate agreement. For this reason, a modeling effort has been made leading to the conclusion that there is room for improvement in the models.     

A new method for the prediction of fade duration statistics in satellite links above 10 GHz

A model for the statistical prediction of fade durations, applicable both to scintillation and rain-induced effects, is presented in this paper. It assumes that durations longer than about 1 minute are lognormally distributed whereas shorter durations follow a power-law distribution. The model is assessed using data contained in the CCIR data bank and from measurements performed with the SIRIO and Olympus satellites. The model is tested using the same data, and the results give multiplicative errors in the range from 0.6 to 1.8 (averages) and from 0.3 to 3.0 (r.m.s.) in the estimation of the fade durations exceeded for fixed probability.     

Annual and diurnal slant path rain attenuation statistics in Athens obtained with the synthetic storm technique

We present annual/seasonal rainfall rate statistics derived from a 29-month data bank of 1 sample/min, measured by a disdrometer located inside the National Technical University of Athens Campus. We discuss both the inaccuracy and the unavailability of the measuring equipment, as well as the statistical reliability of the rainfall rate sample. Additionally, after applying the Synthetic Storm Technique on the measured rainfall rate time series, we present the first long term simulated annual/seasonal and diurnal rain attenuation statistics, at 12 GHz for a hypothetical downlink from Hellas Sat 2 to Athens. According to the results, we predict that communication downlinks working in the afternoon and early evening hours must be given an extra power margin, to compensate for high rain attenuation.     

Rain attenuation successive fade durations and time intervals between fades in a satellite-Earth link

Long-term attenuation data at 11.6 GHz, obtained in a Sirio link, are analysed to provide information on the joint statistics between successive fade durations within a rain event (intrafade) and between different rain events (interfade). The results show that successive fade durations and the interfade or intrafade intervals are approximately statistically independent. Within the same rain event, interfades and fade durations longer than 10 s are statistically identical. These data may be important for planning adaptive systems and for devising prediction models of the dynamic behaviour of rain attenuation.     

A new method of estimating microwave attenuation over a slant propagation path based on rain gauge data

A basic problem in estimating the microwave attenuation over a satellite-earth propagation path on the basis of rain gauge data is that, for a given precipitation event, the attenuation and the rainfall records very often do not have consistent detailed correlation. Such inconsistencies can be greatly reduced if the falling speed of the rain drops, i.e., 2 to 9 m/s for drop sizes of 0.05 to 0.7 cm, is taken into account. Adjustments in time and drop size spectrum are needed for data collected from field rain gauges to realize the actual rainfall along the slant path for correlating rain gauge data with measured satellite signals.     

Yearly variations of rain-rate statistics at Wallops Island and their impact on modeled slant path attenuation distributions

Rain gauge measurements at Wallops Island, VA over a five-year period have been reduced and cumulative rain-date distributions have been determined for yearly, successively combined years, and overall average cases. Yearly variations of the predicted slant path attenuation statistics for two International Radio Consultative Committee (CCIR) models (referred to as modified method I and method II) and the global model at 28.56 GHz were calculated using the yearly measured rain rates at Wallops Island. This frequency was selected as it coincided with the beacon frequency of the COMSTAR geostationary satellite which was also simultaneously monitored at Wallops Island for a period of three years enabling a comparison with the measured rain-fade statistics. The year to year variations of the predicted fades as well as the percent deviations relative to the five-year average case were examined.     

1.06μm激光的斜程大气衰减

根据大气透过率计算软件-CIRTRAN计算了乡村、城市、海洋和沙漠四类地区不同能见度条件下的1.06μm激光斜程大气透过率,经过分析和归纳,提出了一个直观而简便的计算公式.用三种不同的测量方法和LOWTRAN7作比较,证明该公式具有很好的准确度.     

激光斜程湍流大气传输平均偏振起伏

运用光子密度分布函数和采用大气折射率起伏Von Karmam湍流谱、研究了相干激光通过斜程大气传输时的平均量子偏振起伏。通过唯象方法导出大气折射起伏对光场相位调制关系,从而建立了斜程大气光子密度分布函数模型。基于斜程湍流大气光子密度分布函数导出了平均＂量子偏振度＂的解析关系。结果指出：湍流大气导致光束偏振度起伏满足零均值高斯分布,大气湍流不影响光子偏振度统计平均值。     

Space diversity and fade duration statistics at C-band fortwo overwater, line-of-sight propagation paths in the mid-Atlantic coast

The authors characterize space diversity and fade duration statistics at 4.7 GHz for two line-of-sight (LOS) overwater links in the mid-Atlantic coast of the United States. Single-terminal and joint probabilities are generated for both annual and monthly cases for fade and fade duration distributions over the year period from June 1, 1989 to May 31, 1990. The fade and duration distributions during the months November-June were heavily biased by sustained deep fade events. These events were caused by persistent and severe subrefraction, which generally existed simultaneously over both sites. Although the height geometries are dissimilar (13.7 m and 45.5 m), these events mitigated the effectiveness of space diversity. During periods in February and March 1990, for example, fading continuously exceeded 20 dB (relative to the free-space power) at both sites for a duration in excess of 24 h. Space diversity does however appear effective during those months in which fading were predominantly caused by ducting (July-October) and when sustained deep fade events were generally not present     

电磁空心光束在湍流大气中的斜程传输特性

利用扩展的Huygens-Fresnel原理以及维格纳分 布函数(WDF)的二阶矩理论,推导出电 磁空心光束(PCEHB)在非均匀湍流大气中传输的均方根空间扩展、均方根角扩展和M²因子的 解析式。并数值模拟和分析了天顶角、光束阶数、湍流内尺度、波长、束腰宽度、初始相干 长度和初始偏振度对光束质量的影响。研究结果表明,随着天顶角的减小和初始偏振度的增 加,PCEHB的相对均方根空间扩展、相对均方根角扩展和相对M 2因子越小,光束受湍流的影 响越小。且初始偏振度对相对M²因子的影响小于相对均方根空间扩展和均方根角扩展。M²因 子也随着天顶角的增加而增加,当天顶角大于1时对M²因子的影响迅速增加。研究还发现 , 相对M²因子随着光束阶数、湍流内尺寸、波长和束腰宽度的增加,相干长度的减小而减小 。相对M²因子受天顶角和束腰宽度的影响大于其他参数。     

11- and 18-GHz radio wave attenuation due to precipitation on a slant path

Measurements of attenuation at 11 and 18 GHz from precipitation have been made on a slant path over a three-year period in the Tokyo area using a sun tracker and a radiometer. Simultaneous rain attenuation measurements of a 2.9-km terrestrial path at 19 GHz were used to clarify the correlation characteristics between the terrestrial and the slant paths. The following results are presented: frequency, seasonal, annual, and elevation angle dependence of rain attenuation, rain rate distribution, effective distance, correlation characteristics of attenuation between slant and terrestrial paths, attenuation due to snowfall, and site diversity effect for a separation of 14.3 km at 18 GHz.     

Radar and atmospheric electricity measurements associated with microwave attenuation and cross-polarization observed on a slant path

The present paper describes experiments performed near Paris using a C-band radar aimed at estimating rain attenuation and cross-polarization discrimination of the various ots signals received at Gometz-La-Ville. An empirical relationship between the measured reflectivity factor and attenuation is derived, allowing an experimental prediction. Correlation between radar reflectivity and cross-polarization is also investigated for a convective precipitation cell. In addition, electrostatic field measurements show a relation between fade depth and electric field intensity.