First look: South Korea's Electronics and Telecommunications Research Institute has reported a milestone in underground communications, demonstrating wireless data transmission 100 meters (328 feet) below the surface using magnetic fields. Its engineers have developed a new through-the-earth communication system using magnetic induction rather than traditional radio frequencies.
Traditional radio-based systems often suffer severe attenuation underground, as soil and rock absorb or scatter electromagnetic waves. By contrast, magnetic induction uses low-frequency magnetic fields that can propagate through solid ground with less attenuation than conventional radio waves.
ETRI's test setup used a relatively simple configuration. The system employs a loop transmitter antenna roughly 1 meter across and a compact magnetic-field sensor for receiving signals. Data transmission used quadrature phase-shift keying (QPSK) modulation, a common digital modulation scheme, to maintain signal integrity.
Even though the data rate is just 2 kilobits per second, the experiment's success in a limestone bedrock environment, which effectively blocks many radio signals, showed that the approach could work in challenging underground conditions.
The ETRI team demonstrated shorter-range underground wireless communication in 2023 and has since expanded that work with the current magnetit field – based system. In related tests, the researchers previously demonstrated wireless communication over distances of about 40 meters in challenging environments. In the latest work, the researchers used a low-frequency magnetic field-based method that enables communication over 100 meters underground.
Through-the-earth communication (TTE) systems already exist in mining and emergency operations, often relying on relatively high transmission power and specialized equipment to maintain contact over limited distances. ETRI's low-frequency magnetic field approach raises the possibility that future implementations could be integrated into smaller, more mobile devices.
According to the institute, the technology could be applied in areas such as rescue operations, underground facilities, offshore drilling, and national defense. If successfully deployed, the technology could give first responders and workers in underground locations a way to maintain communication in places where conventional wireless networks fail. The research team has also identified potential applications in offshore drilling and national defense.
While current data speeds are limited to a few kilobits per second, suitable for low-bandwidth services such as voice and basic data, the work points toward underground networks that could operate where Wi-Fi, cellular, and satellite signals cannot reach.
The findings were reported in a paper available on IEEE Xplore.