Statistical combination of attenuations by multiple atmospheric effects

At frequencies above 10 GHz, traditional techniques for estimating losses due to atmospheric effects focus on the dominant source of fading, rain attenuation. An approach different from the traditional procedure for calculating attenuation in considered in this paper. Distributions of attenuation were derived for a theoretical system operating in the Washington, D.C. area with a frequency, f=27.505 GHz and elevation angle, /spl theta/=20.0/spl deg/. Local rain rates were used in conjunction with the global model to create a cumulative distribution function (CDF) of rain attenuation. A mean attenuation due to gaseous absorption was then calculated using MPM 93 (Liebe, 1993) using mean local temperature and relative humidity. Vertical variation in absolute humidity along the path was accounted for using average profiles (Slobin, 1981). The result was summed with the CDF of rain attenuation to produce a statistical distribution of rain attenuation.