Compressive MIMO Beamforming of Data Collected in a Refractive Environment

The phenomenon of ducting is caused by abnormal atmospheric refractivity patterns, and is known to allow electromagnetic (EM) waves to propagate over the horizon with unusually low propagation loss. It is unknown what effect ducting has on multiple input multiple output (MIMO) channels, particularly its effect on multipath propagation in MIMO channels. A high accuracy angle-of-arrival (AoA) and angle-of-departure (AoD) estimation technique for MIMO communications, which we will refer to as compressive MIMO beamforming, was tested on simulated data, then applied to experimental data taken from an over the horizon (OTH) MIMO testbed located in a known ducting hotspot in southern California. The multipath channel was estimated from the receiver data recorded over a period of 18 days, and an analysis was performed on the recorded data. The goal is to observe the evolution of the MIMO multipath channel as atmospheric ducts form and dissipate to gain some understanding of the behavior of channels in a refractive environment. This work is motivated by the idea that some multipath characteristics of MIMO channels within atmospheric ducts could yield important information about the duct. Keypoints: • MIMO channel estimation and beamforming • Influence of refractivity on MIMO channel • Evolution of MIMO channel in refractive environments c ©2017 American Geophysical Union. All Rights Reserved.