Estudo da distribuição da taxa de chuva e da atenuação por chuva em enlaces terrestres no Estado do Maranhão

Abstract

The ITU-R model to calculate the attenuation by rain needed in network design and wireless communication systems operating above 10 GHz such as radio link of satellite communication systems, etc .; considers the rain rate that exceeds 0.01% of an average year in the link path. The ITU-R 837.6 recommendation estimated this rate at a given point from a model that considers the average annual rainfall, rain probability of occurrence in 6 hours and information on the relationship between rainfall data from convective and stratiform systems. On the other hand, there is little information on the impact of changes in the amount of rainfall attenuation due to rain. In this context, in the absence of attenuation measurements of information and rainfall rates in the area to be studied, we used the ITU-R method applying the historical accumulated rainfall data INMET (National Meteorological Institute) collected 12 points state of Maranhao in two periods: 1961-1990 and from 1991 - 2015 and was generated contour maps for the time percentage (1%; 0,1%; 0,01% e 0,001%) by bilinear intepolation. Then applied these rain rates in the main models for calculating attenuation in terrestrial links: ITU-R model, Brazil (3M-2008), Australian and Crane. In a case study, these models were fed information from a link frequency (f = 20 GHz) with a distance of 1 km and circular polarization, with the data of rainfall rate to a percentage of 0,01% obtaining different attenuation values. It was found that, despite the attenuations for rain values with data from the last 25 years result in lower values than the values obtained with the climatological normal, they are still higher than those obtained by the database recommended by ITU-R (reanalysis ERA-40)