Abstract DGP2026-19

Reliable communication remains a critical bottleneck for unmanned systems operating in complex and obstructed environments. For planetary exploration rovers, subterranean mapping robots,
and terrestrial vehicles navigating cluttered or urban terrain, maintaining continuous video and command-and-control (C2) links is a persistent challenge. When a rover enters non-line-of-sight
(NLOS) regions, conventional ground-to-rover links suffer from multipath fading, terrain shadowing, and complete blackouts, leading to loss of situational awareness and compromised mission
safety.

This work presents a novel demonstration of a tethered UAV relay architecture, designed to mitigate these limitations by providing an adaptive, aerial line-of-sight relay node between a rover
and its ground control station (GCS). The system, developed and tested in the Marsyard analogue environment at the European Rover Challenge 2025, integrates three coordinated assets:

(i) A four-wheel drive rover (“Explorer”),

(ii) A tethered multi-rotor UAV (“Loiter”) acting as a communication relay, and

(iii) A support rover (“Mover”) for ground-based power delivery and relative
mobility of the drone.

The experimental design focused on the most demanding communication domain, the wideband video transmission, known for its high data rate and sensitivity to noise compared to telemetry
and narrowband control signals. A controlled comparative test was conducted, where the rover’s onboard video transmitter at 5800 MHz at 25 mW was received directly by the GCS in one
configuration, and via the UAV relay in another. The relay drone simultaneously received the rover’s feed at 5800 MHz and retransmitted it to the GCS at 5740 MHz, ensuring a 60 MHz guard
separation to eliminate channel overlap.

Quantitative link budget analysis confirmed that the relay path produced an effective 10–11 dB improvement in received power at the GCS, corresponding to an order-of-magnitude stronger
signal. The rover-to-relay hop benefited from a +10 dBi high-gain antenna, yielding nearly 18× stronger linear power compared to the baseline direct path. End-to-end, the relay configuration
raised the signal-to-noise ratio (SNR) margin from ~32 dB to ~48 dB, effectively moving from a “usable but fragile” regime to a “robust and resilient” communication link.

Experimental results validated these predictions:

(i) Without the relay, the rover’s video feed exhibited frame drops, noise streaks, and frequent blackouts in cratered terrain.

(ii) With the relay engaged, the video stream was continuous, stable, and free from major distortions, enabling uninterrupted situational awareness. The demonstration was recognized by the ERC Jury with an official Letter of Recognition, highlighting its potential relevance for future ERC tasks and beyond.