Transit-Time Variations in Line-of-Sight Tropospheric Propagation Paths

In a recent paper 1 , J. R. Pierce considered stable synchronization of large digital transmission networks, and pointed out that the realization of such a synchronized network calls for, among other things, more information concerning network transit-time variations. In this paper, we seek extreme values for these variations in line-of-sight propagation paths in order to provide some of this information. Estimates are given for (i) the maximum variation in transit-time, Armnx > which one might expect over the period of a year, and (it) the maximum time derivative, r mnx , which one might encounter. The estimated values are related to digital systems, with most specific examples given for a 500 megabit transmission rate. Variations due to changes in the atmosphere (no precipitation), and those due to rain are discussed separate^. In the longer line-of-sight paths achieved in tandem systems, repeaters are assumed to be stable, that is, the concern herein is with atmospheric variations only. Delays associated with selective fading are not discussed, but they are believed not to exceed the given estimates of the maximum variations. The transit-time r is given by the familiar relationship (1)