DIGITAL LIFE

Researchers achieve 100-meter underground wireless communication

Korean researchers have confirmed that underground wireless communication is possible, moving beyond the terrestrial wireless communication they have primarily focused on until now. This opened up a new wireless channel for confirming the survival of buried people in the event of a collapse of an underground facility such as a mine, conducting underground rescue operations, or conducting underground military operations.

ETRI has succeeded in developing the world's first "magnetic field underground communication source technology" that can transmit and receive voice signals 100 meters underground in a mine using a 1-meter diameter transmitting antenna and a several-centimeter-class receiving antenna.

This technology confirms the feasibility of voice transmission and reception in underground spaces previously inaccessible by wireless technology. Accordingly, this technology is expected to be applied in activities such as rescue operations, military operations, and common utility tunnel safety management.

In particular, this research is based on test results conducted in a limestone bedrock environment where underground communication is known to be virtually impossible, and is considered to have opened up a new area of underground space communication technology, such as rescue operations and military operations.

Underground mines have very severe signal attenuation, making them inaccessible using existing wireless communication technologies.

ETRI focused on the stable transmission of magnetic fields in underground media and developed a low-frequency magnetic field-based communication system.

The researchers implemented communication using a 1-meter-diameter transmitting antenna, a small magnetic field receiving sensor of several centimeters in size, a frequency of approximately 15 kHz, and a data rate of 2–4 kbps, which is sufficient for voice communication.

They successfully conducted bidirectional communication testing within a 100-meter straight-line distance between the mine entrance (ground level) and the fifth underground layer. This is the world's first demonstration that surpasses existing tens-of-meters-level overseas research.

This outcome signifies the possibility of communication between buried people and rescue teams in situations such as underground disasters, including mine collapses.

Also, it can be widely utilized in various fields, such as responding to disasters in common utility tunnels, gas pipelines, and oil pipelines, ensuring communication continuity during military operations in underground bunker environments, and more.

ETRI explained that it is advancing technologies linked to personal devices such as smartphones, and that this will make wireless relays (APs) connecting ground and underground possible.

This technology has been described in the IEEE IoT Journal, and domestic and international patent applications have been completed for key elements such as the transmitter/receiver, antenna, low-frequency modem, and bandwidth expansion technology.

Twelve SCI papers in publication, two presentations at international academic conferences, eight international patents, and technology transfers were accomplished.

Cho In Kui, Principal Researcher of ETRI's EM Wave Basic Technology Research Section, stated, "This is a technology that can significantly reduce the possibility of communication disruption during rescue operations in the event of a mine accident, as much as it has succeeded in communication in underground environments where radio waves do not reach."

Seung Keun Park, Assistant Vice President of ETRI's Radio Research Division, said, "This is an innovative technology necessary not only for mines but also for extreme environments such as tunnels, underground facilities, offshore drilling, and national defense. It will be utilized in various industrial sectors as a highly reliable communication means."

Achieving wireless communication at a depth of 100 meters, typically utilizing low-frequency magnetic induction (MI) or Through-the-Earth (TTE) technology, offers significant advantages in safety, operational efficiency, and environmental monitoring where wired, or high-frequency systems, fail.

Key advantages include(below):

Enhanced mine safety and rescue: The primary advantage is reliable, post-accident communication. Unlike wired systems that break, TTE systems can transmit through hundreds of meters of rock, allowing trapped miners to communicate their location and condition to the surface, and assisting in emergency evacuations.

Deep-earth operation visibility: It enables real-time monitoring of geotechnical data, such as rock stress, gas concentration, and humidity at extreme depths, helping to prevent disasters.

Operational continuity in mining: Deep, wireless nodes can be used to track personnel and manage autonomous machinery at the working face of deep mines, increasing production efficiency without the need for constant maintenance of extensive cabling.

Environmental monitoring (landslides/water): Deep underground sensors can measure pore pressure, moisture levels, and water levels inside dams, providing critical early warning data.

Minimal environmental impact: Because the infrastructure is concealed, it avoids interference with surface operations, such as agricultural tiling or topsoil activity.

High reliability in harsh conditions: Underground communication channels, particularly those using magnetic induction, are less affected by complex tunnel structures or mining-related rubble compared to high-frequency RF systems.

Researchers (such as those at ETRI) are actively developing technologies, including micro-magnetic field communication, to make reliable communication at depths exceeding 100 meters a standard for safety in mines and tunnels

Provided by National Research Council of Science and Technology