Before revision:  Although Magnetic Induction ( MI) communication has been shown to be a promising technique in underground environments, the existing MI system utilizes very large coil antennas, which are not suitable for deployment in underground. In this paper, we propose a metamaterial enhanced magnetic induction communication mechanism that can achieve over meter scale communication range by using millimeter scale coil antennasin the harsh underground environment.
After revision:  Although Magnetic Induction ( M^2I) communication mechanism, where a MI coil antenna is enclosed by a metamaterial shell that can enhance the magnetic fields around the MI transceivers. As a result, the M^2I communication system can achieve tens of meters communication range by using millimeter scale coil antennasin the harsh underground environment.