11-GHz radio: Application of rain attenuation data to 11-GHz Radio path engineering

This paper describes the procedures adopted at Bell Laboratories for using rain attenuation data to engineer 11-GHzz microwave radio hops and routes. Rain outage time charts, which show the rain outage time as a function of rain attenuation and hop length, are the basic tools in engineering the hops. The charts, their formulation, and the procedures for using the charts are described and illustrated with several examples. The procedures are used to demonstrate and quantify the sensitivity of allowable hop lengths to the available rain attenuation margin, the effects of a limited rain attenuation margin, and the effects of the variation in the outage in a single year from the 20-year average outage. Guidelines for judging if a hop or route is performing as engineered are developed.