Measurements of Opportunistic Aircraft Signals and Verification of a Propagation Prediction Tool in Mountainous Region

Automatic dependent surveillance - broadcast (ADS-B) is an emerging and more economically viable means of aeronautical surveillance. Aircraft periodically broadcasts surveillance information such as its own position and velocity. Although ADS-B was originally developed for air traffic control, measurement of opportunistic ADS-B signals can be applied to radio propagation study. This paper presents a comparison on the received signal strength (RSS) between measurements of opportunistic ADS-B signals and predictions by a Physical-Optics-based tool with terrain data in the Himalayan mountains of Bhutan. Two measurement scenarios were studied: one with the receiver at the airport located in the bottom of a mountainous valley and another with the receiver on the top of a mountain that surrounds the valley. The comparison is aimed at 1) investigating the ADS-B signal propagation in the mountainous region, 2) demonstrating a site-survey by opportunistic ADS-B signals, and 3) demonstrating verification of a propagation prediction tool.