Optimal Positioning of Hovering UAV Relays for Mitigation of Pointing Error in Free-Space Optical Communications

Abstract

The relay positions or hop distances in a multihop relaying scheme is an important parameter that can be optimized in order to mitigate the angle-of-arrival variance or pointing error in a free-space optical (FSO) backhaul link. In this study, we have optimized the relay positions for amplify-andforward and decode-and-forward relays in a multi-hop unmanned aerial vehicle-based relaying scheme for FSO. Particularly, we have shown that a significant performance improvement may be achieved by optimizing the outage probability as a function of the hop distance for amplify-and-forward relays when the relays are constrained by a finite power gain. Additionally, we have discovered that for a low signal-to-noise ratio channel, the optimal hop distance of a particular hop for decode-and-forward relays is inversely proportional to angle-of-arrival variance in that hop.

Optical Wireless Communications: Illuminating the Path for Cooper's Law

“…For instance, the study [241] proposed mitigation of pointing error by optimizing the beamwidth of transmitted Gaussian beam. The study [242] proposes mitigation of pointing error loss by optimizing the aerial relay locations in the stratosphere.…”

“…Quadcopters or hovering UAVs can be deployed effectively as aerial relays in FSO backhaul links or as access points at the user end. The performance of UAV based amplify-andforward and decode-and-forward relays have been analyzed in [243] and [242], respectively, under different optical channel conditions. UAVs can also be effectively placed to avoid the line-of-sight issue in a dense urban environment, and by optimizing the locations of the UAVs, significant performance gains can be achieved [244].…”

Lidar-Assisted Acquisition of Mobile Airborne FSO Terminals in a GPS-Denied Environment

“…Unmanned aerial vehicles (UAVs) will continue to find major applications in 6G and beyond wireless communication systems [6], [7]. A major application of UAVs involves provision of connectivity to farflung/hard-to-reach areas where it will not be possible to connect the remote region with conventional tower-and-cable infrastructure.…”

Optimal Power Allocation Between Beam Tracking and Symbol Detection Channels in a Free-Space Optical Communications Receiver

“…Assuming that the pointing error (due to angle-of-arrival fluctuations) is distributed as a Rayleigh random variable [15], [28], [29], the received signal power-denoted by P s -captured by the detector is furnished by the relationship:…”

“…The authors in [24], [25] consider generalized models of pointing error for capacity calculations, whereas [26], [27] consider pointing error modeling along with turbulence induced fading in FSO links. The authors in [28], [29] exclusively consider Rayleigh distribution-based pointing error model for dual and multihop relaying FSO channels that involve hovering unmanned aerial (UAV) based relays. The study…”