An Analysis of Conditional Site Diversity: A Study at Ka-Band

The use of EHF and SHF frequencies above 20 GHz is becoming increasingly important for high-capacity communication systems. Whether these systems are slant-path links, terrestrial fixed links, or deep-space links, the high bandwidths available and the relatively low spectral congestion are very attractive. One of the main disadvantages of these frequency bands is that the attenuation caused by meteorological effects can become significant, and the attenuation caused by clouds, rain, and atmospheric gases becomes very large. The largest attenuation events are caused by rain and clouds with a high liquid water content. In order to provide high-availability links, it is possible to use site diversity, by providing two spatially independent terminals. The spatial separation of the terminals reduces the probability of both terminals being faded. In this paper, we present an analysis of two spatially unique measurements of a satellite-based 20.7-GHz beacon. The results show that even at modest separations there is still the opportunity for significant availability improvements using site diversity. The probability density functions (pdfs) conditioned on the single-site attenuation level are presented. These demonstrate a characteristic shape and could form the basis of future modeling approaches.