Title

Air-Ground Channel Characterization for Unmanned Aircraft Systems—Part III: The Suburban and Near-Urban Environments

Document Type

Article

Subject Area(s)

Electrical engineering

Abstract

Applications for unmanned aircraft systems (UAS), or “drones,” are increasing rapidly. In order to provide safe and reliable links to integrate UAS into the National Airspace System (NAS), control and non-payload communication (CNPC) system requirements are being specified. A comprehensive knowledge of the air to ground (AG) channels in the bands of interest (C- and L-band) plays an essential role. NASA Glenn Research Center has sponsored an AG channel measurement campaign for most of the typical ground site (GS) local environments, including over water [8], hilly/mountainous [9], suburban, and near-urban. As a continuation of our prior work, this paper addresses the suburban and near-urban scenarios. Our developed AG channel models include path loss, small scale fading Ricean K-factors, spatial and inter-frequency correlations for multiple aircraft antennas, root mean square (RMS) delay spread and wideband tapped delay line (TDL) models. The path loss is described by either log-distance or two ray models, with small corrections for flight direction. The K-factors were 12 (14) dB in L-band and 27.4 (28.5) dB in C-band in near-urban (suburban) environments. The inter-band signals were uncorrelated, but the intra-band signals were highly correlated, with median correlation coefficient greater than 0.85. The C-band RMS delay spread was on average 10 to 60 nanoseconds with maximum of approximately 4 microseconds. The TDL models are composed of the line-of-sight (LOS) component, a ground reflection, and up to seven intermittent multipath components (MPCs). Relative power, phase, occurrence probability, duration, and excess delays for these intermittent MPCs are quantified. An algorithm to simulate the AG channel impulse response (CIR) via the TDL models is provided.

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