An engineering method is proposed for calculating rain attenuation distributions for frequencies greater than 10 GHz and for paths of arbitrary length. The technique is based upon the observed approximate lognormality of rain attenuation and rain rate statistics within the range of interest; it reflects local meteorology through incorporation of the observed point rain rate distribution. Some important parameters in the resulting formulas are determined empirically from experimental data. Sample calculated results agree well with available experimental data from Georgia, New Jersey, and Massachusetts. This new technique may prove useful for engineering radio paths at frequencies above 10 GHz. Sample calculations of expected outage probability are given for 11‐ and 18‐GHz radio links at Atlanta, Georgia, as a function of repeater spacing and transmission polarization.

Two methods are described to obtain long-term (>20years) distri butions of 5-minute point rain rates from data published by the Na tional Climatic Center for U.S. locations. A set of simple empirical formulas for converting the distribution of 5-minute rain rates into rain attenuation distributions on 11-GHz radio paths has been deduced from data measured in Georgia. Additional data measured in several other locations also support this empirical formulation.These simple formulas and 5-minute point rain rate distributions are useful for path engineering of 11-GHz radio. The work on rain rate distributions dis cussed in the paper derives from approaches suggested by the late W. Y.S.Chen. - 9- 16

Thirty-one sets of experimental data on the statistics of microwave rain attemiaiion at frequencies above 10 GHz, in the U.S.A., England, Japan, Italy, and Canada, indicate that, (i) the distribution of rain attenuation a, in dB, is approximately lognormal with a standard deviation Oa of hg\o a ranging from O.46 to 0.71 for earth-space paths, and from O.SS to 0.86 for terrestrial paths; (ii) the distribution of the rain fade duration τ is also approximately lognormal with a standard deviation σ, of logio τ ranging from 0.44 to 0.76 for both earth-space paths and terrestrial paths. We propose a theory to exphin this general behavior. A theoretical upper bound for the fade duration distribution in the tail region is also given.The findings in this paper simplify the determination of rain attenua tion statistics needed for the design of earth-satellite radio links and ter restrial radio links.

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An extension of a ?nethod of Chen and