Korean researchers 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 announced that it 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 15kHz, and a data rate of 2-4kbps, 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 persons 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 at 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, an international academic journal in the field of communications, 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. 12 SCI papers in publication, 2 presentations at international academic conferences, 8 international patents, and technology transfer 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, also 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.”
1) 15kHz: It is a very low-frequency band with a very small bandwidth, not the MHz or GHz range commonly used in general wireless communication. It is a frequency band designed to reduce medium losses and transmit data in underground or underwater environments, taking into account factors such as antenna size.
2) 4kbps: It is a data size sufficient to send voice data (applied only to uplink) and is comparable to the level of data transmitted and received by pressing a radio button.
3) IEEE IoT Journal: “Wideband Magnetic Induction Wireless Communications in Challenging Underground Environments: A Current-Driven Scheme.