Adaptive Diversity Combining for Improved Millimeter Wave Communication through Rain

Under severe rain conditions there may be significant amounts of multiply-scattered millimeter wave radiation present in the vicinity of the receiving antenna for a satellite downlink. This paper explores angle diversity reception of the scattered radiation as an alternative to spatial (multiple site) diversity for ameliorating rain attenuation. Results from scalar plane-wave transport theory for the attenuation, angle-of-arrival spread, multipath spread, and Doppler spread of the scattered field are summarized. When combined with a diversity reception communication analysis, these solutions imply that a large performance gain over nondiversity reception can be achieved if adaptive coherent combining can successfully be employed. Although this gain does not require multiple receiver sites, it does entail a transmission bandwidth reduction.