LoRa Propagation and Coverage Measurements in Underground Potash Salt Room-and-Pillar Mines

Area of Science:

• Electrical Engineering
• Mining Engineering
• Wireless Communication

Background:

• Digitalization in mining necessitates reliable communication for autonomous systems.
• Long Range (LoRa) technology offers potential for underground sensor networks due to its signal range and sub-GHz frequencies.
• Understanding LoRa's underground propagation is crucial for its successful implementation.

Purpose of the Study:

• To evaluate the applicability and propagation behavior of LoRa in active salt mines.
• To identify environmental effects influencing LoRa signals underground.
• To analyze LoRa's performance at a macroscopic level in a unique mining environment.

Main Methods:

• Conducted measurements of LoRa (868 MHz) packet loss and signal strength in various line-of-sight and non-line-of-sight configurations.
• Utilized omni-directional antennas in an active salt and potash mine (Werra, Germany).
• Analyzed signal propagation over entire mining sections exceeding 1000m.

Main Results:

• LoRa demonstrated a distinctive waveguide-like propagation effect in salt mines, with signals reflecting off salt formations.
• Successful LoRa communication was achieved over 1000m with less than 15% packet loss in non-line-of-sight conditions within room-and-pillar structures.
• Consistent path loss was observed across different materials and tunnel geometries, indicated by Δ50dBm values.

Conclusions:

• LoRa technology is highly suitable for underground sensor networks in salt mines.
• The observed waveguide effect in mining drifts significantly enhances signal propagation, potentially outperforming urban or indoor environments.
• Further research into LoRa's underground performance is warranted due to its promising results.