Radar prediction of absolute rain fade distributions for Earth-satellite paths and general methods for extrapolation of fade statistics to other locations

Abstract
Two distinct prediction methods are described. The first deals with a technique for establishing absolute fade statistics at a given site using a sampled radar data base. The second is a method for extrapolating absolute fade statistics from one location to another given simultaneously measured fade and rain-rate statistics at the former. Both methods employ similar conditional fade statistic concepts and use long term rain-rate distributious. The radar-predicted levels showed good agreement in probabilities associated with the cumulative fade distribution when compared to directly measured levels of the COMSTAR beacon at 28.56 GHz for the Wallops Island, VA, radar facility, Probability deviations ranging from 2 to 19 percent with an average of 11 percent were obtained upon comparing measured and predicted levels at given attenuations. The extrapolation method was tested employing the Wallops Island measured rain-rate statistics and fade distributious at 28.56 GHz. The method was also tested at 19.04 GHz using measured results for Austin, TX. The extrapolation of fade distributions to other locations at 28 GHz showed very good agreement with measured data at three sites located in the continental temperate region (average probability deviations of 11.5, 9, and 17 percent) and respectable agreement atone site in a wet subtropical region (30 percent deviation). At 19.04GHz,extrapolated levels were generally not as good as at 28 GHz (41, 28, 7, and 27 percent), although they were still quite respectable.