Advances in microwave radio route engineering for rain.

In the mid 1970's a set of studies of rain attenuation on line- of-sight microwave radio links was undertaken by a number of organizations of Bell Laboratories. The culmination of this work was a set of design charts for 11 GHz radio that was issued in 1975. During the last two years there has been a growing interest in the use of the 18 and 23 GHz bands for local access digital radio. Analysis of the 11 GHz charts revealed serious flaws in the rain rate distributions for the low rain rates that are critically important to the application at 18 and 23 GHz. This memorandum describes the results of a study undertaken to correct these flaws and to generalize the methodology for estimating outage due to rain attenuation.