Prediction Of Rain Attenuation Statistics Research Articles

Rain attenuation measurements: Variability and data quality assessment

Year‐to‐year variations in the cumulative distributions of rain rate or rain attenuation are evident in any of the published measurements for a single propagation path which span a period of several years of observation. These variations must be described by models for the prediction of rain attenuation statistics. Now that a large measurement data base has been assembled by the International Radio Consultative Committee (CCIR), the information needed to assess variability is available. On the basis of 317 sample cumulative distribution functions (cdf's) for the occurrence of attenuation by rain, the expected year‐to‐year variation in attenuation at a fixed probability level in the 0.001–1.0% of a year range is estimated to be 26%. The expected deviation from the predictions of any of the better attenuation models for a single year of observations is estimated to exceed 34% when a rain climate model is employed to estimate the rain rate cdf. The probability distribution for the variation in attenuation or rain rate at a fixed probability level is lognormal. The lognormal behavior of the deviations was used to compile statistics for variability, to establish hypothesis tests for identifying outliers—the observed sample cdf that deviates significantly from the expected (modeled) cdf, and to predict the attenuation level to be exceeded with a specified return period.

Prediction of rain attenuation statistics for satellite communications in the 10–45 GHz range in Canada

Presents a means of predicting rain attenuation for a 20/44 GHz SATCOM system for Canada. Rain attenuation statistics have been estimated, but not verified experimentally, for most of the Canadian territory below 69°N latitude for a geostationary SATCOM system in the 10-45 GHz range with arbitrary link parameters. The effect of site diversity on these results can be estimated. Long-term experimental rain data, the International Radio Consultative Committee (CCIR) rain attenuation prediction model and the Hodge (1982) site diversity model have been used for this purpose in the present work. The results are given in various formats to facilitate system design. This study indicates that although rain attenuation is high in this frequency range, it remains within manageable limits.

Measurements of cloud contribution to rain millimeter wave attenuation by using a radar and radiometers

The measurement technique of cloud contribution to rain attenuation and the equipment consisted of the coherent pulse Doppler radar at wavelength λ=3.2 cm, the radiometers at λ=0.4; 0.8 and 1.35 cm and apparatus for signal recording and processing is described. The results of such measurements are given. The Doppler spectrum of the rain backscattered radar signal was used for determination of rain drop size distribution height profile then rain attenuation was calculated and cloud attenuation was determined as the difference between the total attenuation measured by using the radiometers and rain attenuation. The results of this work gave possibility to improve the known rain model of P.Misme for prediction of rain attenuation statistics for Earth-satellite links at millimeter wave.

A simple rain attenuation model for earth‐space radio links operating at 10–35 GHz

The simple attenuation model has been improved from an earlier version and now includes the effect of wave polarization. The model is for the prediction of rain attenuation statistics on earth‐space communication links operating in the 10–35 GHz band. Simple calculations produce attenuation values as a function of average rain rate. These together with rain rate statistics (either measured or predicted) can be used to predict annual rain attenuation statistics. In this paper model predictions are compared to measured data from a data base of 62 experiments performed in the U.S., Europe, and Japan. Comparisons are also made to predictions from other models.

Theoretical random process for prediction of rain attenuation statistics in site diversity satellite links above 10 GHz

Site diversity systems are foreseen for earth-to-satellite links in localities with high rain-induced attenuation operating at frequencies above 10 GHz. An analytical model for the rain-rate statistical process is developed using radar-derived information on the rain structure collected at Spino d'Adda in the framework of the Sirio experiment. The procedure for estimating rain attenuation in both single and site diversity systems is outlined in a general formulation which makes it applicable to different situations. The model gives results very similar to experimental ones.

The prediction of rain attenuation statistics

The prediction of rain attenuation statistics is a question of meteorology and probability. Therefore, the possible accuracy of these predictions depends on the knowledge of meteorological mechanisms and data as well as on the statistical uncertainty due to the stochastic nature of meteorological events. Attenuations exceeded for less than 0.1 % of the time within the worst-month are caused by meteorological phenomena which are not well known. Experimental and theoretical investigations show that the inaccuracy is of the same order as the unavoidable statistical uncertainty.

Frequency dependence of effective path length in prediction of rain attenuation statistics

Theoretical and numerical results are presented which demonstrate that the effective path length commonly used in the prediction of rain attenuation statistics for earth-space paths is frequency dependent. Also presented is a method of translating effective path length measurements in frequency.