Wideband Magnetic Induction Wireless Communications in Challenging Underground Environments: A Current-Driven Scheme

This article presents wideband magnetic induction (MI) wireless communications for data transmission from underground to ground level. In MI wireless communication, lowering the carrier frequency mitigates eddy current losses, improving magnetic field penetration and facilitating more effective traversal through conductive materials, ultimately extending the communication range. However, in conventional voltage-driven schemes, this decrease in frequency typically results in reduced bandwidth, limiting the achievable data transmission rate. To overcome this limitation, we propose a current-driven scheme that maintains a constant transmitter coil current across a wide frequency range, resulting in a higher data rate. In addition, since reactive power circulates within the resonant tank, it can generate high voltage and current levels with low power consumption, allowing data transmission over long distances. Our main focus is to increase bandwidth and communication distance from system-level perspective. Field experiments were conducted using a fully operational wireless communication system with practical signal transmission and processing capabilities, using small transmitter loop antenna of 0.9-m by 0.9-meters to transmit signals from 100 m underground to the ground level. Quadrature phase-shift keying modulation was used to transmit and receive data at a rate of 2 Kb/s with a low carrier frequency of 15 kHz. This corresponds to a data rate-to-carrier frequency ratio of 13.33%, demonstrating the feasibility of wideband wireless communication using the proposed scheme. An energy per bit-to-noise power spectral density ratio of 23.98 dB and an error vector magnitude of 14.74% were measured, indicating that the proposed system was sufficiently reliable.