Demonstration and application of diffusive and ballistic wave propagation for drone-to-ground and drone-to-drone wireless communications

Peter J Burke

doi:10.1038/s41598-020-71733-0

Abstract

In order to determine how an electromagnetic wave propagates from a base station to a cell phone or a wirelessly connected device, we use a novel Unmanned Aerial Vehicle (UAV) mapping technology to map the cellular network coverage at various altitudes in various terrains (flat, hilly, mountainous). For the flat terrains, the waves are shown to propagate ballistically: They have an altitude independent path loss consistent with minimal scatter in the propagation from transmitter to (aerial) receiver. In mountainous terrain, the waves are shown to propagate in the diffuse regime, and demonstrate a 10 dB increase in received signal intensity per 100′ of altitude gain, up to 400′. In the intermediate case, evidence of coherent wave interference is clearly observed in altitude independent interference patterns. These general observations can be used to build a physical or empirical model for drone-to-ground and drone-to-drone propagation, for which existing models are shown to fail. While important for building physical models of wave propagation in wireless networks, this method can be used more generally to determine the magnitude and phase of an electromagnetic wave at every point in space, as well as usher in the era of drone-to-ground and drone-to-drone communications.

Highlights

The other definition of absorption is where energy is lost due to resistive currents in scattering centers, like a black body absorbing rather reflecting light. (We recently demonstrated this regime by perfectly impedance matching a material to free space to get of order unity absorption of R F20, but this is not normally the case in the physical world we live in.) Because this is not typically the case in the RF regime, it is unlikely to be a significant contributor to signal loss, and has not been modeled in the industry standard Hata-COST321 and refinement models, and is not considered as a significant effect here
The models are not developed yet, we have shown three significant aspects that appear in physical reality: Ballistic wave propagation, diffusive wave propagation, and strong interference of only a few paths
The FAA is even proposing to require an internet connection for some or all drones, which would lead to millions of internet connected drones, making the requirement of a realistic propagation model imperative for the future safety and economy of all aviation

Summary

Methods

Details of the vehicle and the methods are presented in another p aper[11]. The system is a 600 mm flying wing with an STM32 F4 based bit flight controller running Ardupilot with GPS and autopilot capabilities capable of complete autonomous flight, from takeoff waypoints to landings. An on-board Linux companion single board computer (Raspberry Pi Zero W) handles communication with the 4G modem and internet. The UAV can be piloted remotely via a separate 900 MHz transmitter or via the 4G internet connection over the internet.

Results

Discussion

Conclusion