Limited feedback multi-stage beam-forming method for beyond-Line-of-Sight ducting channels

Atmospheric duct is a layer in which propagating signals are refracted back to the surface. In this way, these signals are trapped between surface and duct layer. Thus, atmospheric ducts significantly limit spreading of propagating signals, and provide lower path-loss compared to standard atmosphere even at beyond-Line-of-Sight (b-LoS) ranges. Since duct formation is highly probable in regions with high humidity such as coastal and maritime areas, atmospheric ducts can be used as a communication medium especially for naval beyond-Line-of-Sight (b-LoS) links. Trapping effect of atmospheric ducts provides very narrow angle-of-arrival (AoA) span, thus large planar antenna arrays can be utilized to provide sharp electronically steerable beams. To this end, we propose a limited feedback multi-stage beam-forming method for ducting channels for the first time in the literature. At the end, we present simulation results for the spectral efficiency of ducting channels with the proposed method.