Earth Terminal-to-Satellite Link Availability using New Rain Event Duration Statistics

As conventional frequency bands become crowded or fail to yield the required performance, commercial and military earth terminal to satellite communications links are entering the EHF domain. Although EHF links can offer significant advantages over lower frequency links, they also suffer reduced availability caused by rain attenuation. The study reported in this paper uses the Crane model and applies local rain statistics in order to assess local link availability. Year to year outage time varies on the order of 10 to 1. Monthly outage times can be about 10 times the yearly percentage of outage times and weekly outage times can be about 5 times the monthly. An investigation of some short-term single rain event duration statistics at specific locations indicates that if connectivity must occur within a certain period, then functional availability defined in this way can be greater than the "on demand" average availability. Analysis of existing data reveals statistics on the likelihood of occurrence and duration of single outage events.