Received Power Characterization of Terrestrial Cellular Signals on High Altitude Aircraft

Abstract

The received power of terrestrial cellular 3G code division multiple access (CDMA) and 4G long-term evolution (LTE) signals on a high altitude aircraft is experimentally characterized. The conducted experiments were performed on a Beechcraft C-12 Huron, a fixed-wing U.S. Air Force aircraft. Two types of flight patterns were performed: (i) teardrop-like patterns to characterize the carrier-to-noise ratio <tex>$(C/N_{0})$</tex> versus altitude and (ii) grid-like patterns to characterize <tex>$C/N_{0}$</tex> versus the horizontal distance between the aircraft and cellular towers. Flight campaigns in two regions were conducted: (i) a rural region in Edwards, California, USA, and (ii) an urban region in Riverside, California, USA. It was observed that cellular signals are surprisingly powerful at both (i) high altitudes, exhibiting <tex>$C/N_{0}$</tex> of 25&#x2013;55 dB-Hz at altitudes of 2,000-23,000 ft above ground level (AGL) and (ii) faraway horizontal distances, exhibiting <tex>$C/N_{0}$</tex> of about 30 dB-Hz for towers as far as 50 km, while flying at about 16,000 ft AGL. In addition, two propagation models were evaluated to describe the behavior of the measured <tex>$C/N_{0}$</tex>: (i) free-space path loss model and (ii) two-ray model. It was observed that the two-ray model fits the measured <tex>$C/N_{0}$</tex> sufficiently well, for towers more than 10 km away, while flying at an altitude of 16,000 ft AGL. For towers closer than 10 km, the antenna radiation pattern should be incorporated into the two-ray model to improve model fitting.