| Category | Applied link (segment) | Distance (km) | Terrain/LOS condition | SNR/RSSI | Data transmission result | Interpretation |
|---|---|---|---|---|---|---|
| Failure (LOS blocked) | Relay UAV-Recon UAV | ～3.9 | A higher ridge (～995 m) near the relay-UAV position (elevation ～1,016 m AMSL) obstructed the propagation path | ≤11 dB/～−79 dBm | Text: stable Video: unstable (degraded) | Link quality was dominated by terrain-induced LOS blockage rather than distance |
| Relay repositioning (LOS secured) | Command post-Relay UAV (and relay-assisted link) | ～4.6 | The relay UAV was repositioned to secure LOS toward the command post | ≥30 dB/～−56 dBm | Text: stable Video: varies with traffic load | Securing LOS substantially increased the link margin even at a longer distance |
| Traffic bottleneck (data-type effect) | Traffic concentrated at relay node (Recon UAV/quadruped robot → Relay UAV) | - | Traffic-load effects were observed even under favorable LOS and link conditions | Link quality favorable | Text: stable Video (EO/IR): frame drops and latency | Channel capacity/occupancy becomes a key bottleneck for multi-stream video transmission |