Technical analysis and engineering reference.
When search-and-rescue teams penetrate deep canyon ravines or collapsed concrete urban rubble, ground RF signals are completely blocked by terrain. A single tethered drone cannot see both the deep canyon floor and the distant base camp simultaneously. Multi-drone relay chains solve this by self-organizing in space.
U2URelay coordinates drone positions using distributed Particle Swarm Optimization (PSO): - Fitness function balances radio link signal-to-noise ratio (SNR), remaining battery energy, and wind turbulence compensation margins. - Drones continuously adjust altitude and horizontal stand-off distance to hover directly in the RF line-of-sight sweet spot. - If a relay drone's battery reaches 20%, it autonomously summons a fresh relief drone from the ground nest, performing an in-flight link handover with zero dropped video frames.
The highest-altitude drone in the swarm operates an S-band satellite transceiver, bridging the local FANET directly into sovereign military satellites or commercial LEO constellations for global reachback.