Energy Optimization of a Laser-Powered Hovering-UAV Relay in Optical
Wireless Backhaul
Abstract
Due to their flexibility and low cost deployment, unmanned aerial
vehicles (UAV) will most likely act as base stations and backhaul relays
in the next generation of wireless communication systems. However, these
UAVs—in the untethered mode—can only operate for a finite time due
to limited energy they carry in their batteries. In free-space optical
communications, one solution is to transport both the data and the
energy from the source to the UAV through the laser beam—a concept
known as simultaneous lightwave information and power transfer
(SLIPT). In this study, we have analyzed the SLIPT scheme for
laser-powered decode-and-forward UAV relays in an optical wireless
backhaul. The major goal of this study is to optimally allocate the
received beam energy between the decoding circuit, the transmitting
circuit and the rotor block of the relay in order to maximize a
quality-of-service metric such as maximum achievable rate, outage or
error probabilities. As expected, we note that the optimal power
allocation depends heavily on the source-relay and relay-destination
channel conditions. In the final part of this study, we have maximized
the operational time of the UAV relay given that the maximum achievable
rate stays above a certain threshold in order to meet a minimum
quality-of-service requirement.