Development and Field Testing of a Robust UAV Relay-Assisted Hybrid FSO/RF System for Emergency Communications

Conventional emergency communication networks are plagued by critical limitations, including protracted recovery cycles and coverage voids, which are further exacerbated by the escalating frequency of natural disasters and public safety incidents. To address these challenges, we propose an unmanned aerial vehicle relay-assisted hybrid free-space optical (FSO)/radio-frequency (RF) system engineered for rapid deployment and robust performance in emergency scenarios. In this architecture, FSO links form the high-capacity aerial backbone, while RF channels deliver last-mile connectivity to end users. Furthermore, a unified end-to-end channel model is developed to analytically integrate the effects of fiber attenuation, atmospheric turbulence, and RF path loss, establishing closed form relationships between received signal-to-noise ratio and bit error rate. Field experiments validate zero-bit-error transmission on the 100 m FSO relay link, a sustained downlink rate of 127.48 Mbps, and stable coverage, which collectively underscore the system's effectiveness for resilient, high-throughput emergency communications.