IEEE Transactions on Vehicular Technology · 2017 · 108 citations · 11 references
EngineeringAerospace EngineeringAvionicsUnmanned Aircraft SystemsWireless CommunicationsGround Wave PropagationWireless Channel ModelingChannel CharacterizationDelay SpreadFadingPath LossPath Loss ModelingPropagation Path LossShadowingSmall-scale Fading
Unmanned aircraft systems are projected to expand rapidly, and prior AG channel studies have characterized path loss, fading, and delay spread, but the specific phenomenon of airframe shadowing—where the aircraft itself blocks line‑of‑sight signals during certain maneuvers—remains underexplored. The study aims to characterize airframe shadowing in medium‑sized aircraft by extending previous AG channel measurements. Using data from over 200 wing/engine shadowing events collected in C‑band (5060 MHz) and L‑band (968 MHz), the authors report shadowing depth, duration, diversity gain, and fading statistics, and propose algorithms that generate random shadowing events from depth and duration cumulative density functions. The results show that airframe shadowing loss, exceeding 35 dB and lasting up to 74 s, is independent of ground site and link distance, depends mainly on roll angle, is largely uncorrelated with duration, and can be mitigated by deploying multiple aircraft antennas.
Applications of unmanned aircraft systems (UAS) are expected to expand dramatically in the coming decades. In order to provide safe and reliable links for UAS, NASA Glenn Research Center sponsored a measurement campaign in 2013 to characterize air-ground (AG) channels. In the first three of our AG channel characterization series papers, path loss, small scale fading, stationarity distance, root mean square (RMS) delay spread, spatial correlations, and tapped delay line models were presented for a range of ground site environment. In this paper, we expand the results to a unique and little-studied characteristic of the AG channels-airframe shadowing-for a medium-sized aircraft. Airframe shadowing occurs when the line-of-sight signal is obstructed by the airplane itself in some specific maneuvers. Based on over 200 aircraft wing/engine shadowing events in both C-band (5060 MHz) and L-band (968 MHz) collected in the measurement campaign, shadowing depth, duration, multiple antenna diversity gain, and small scale fading results and their statistics are reported. Algorithms are proposed to simulate a random shadowing event based upon shadowing depth and duration cumulative density functions. Airframe shadowing characteristics are independent of the local ground site conditions and link distance. The shadowing loss is modeled as a function of aircraft roll angle, but shadowing loss and duration are essentially uncorrelated. The maximum shadowing loss measured was over 35 dB and the duration was up to 74 s. As expected, deployment of multiple aircraft antennas is shown helpful to mitigate this shadowing.
11