An Efficient Signal enhancement scheme for Metamaterial-enhanced Magnetic Induction-based underground Wireless Sensor networks

In underground coal mines, sensors are usually deployed in the roof rock layer or coal seam to monitor its states, and wireless sensors show its prominent advantages in massive sensor data acquisition. But these media cause large attenuation for transmitting signals. In view of the short distance of underground MI communication, the metamaterial enhanced magnetic induction communication (M2I) is proven to improve the coupling efficiency between the receiver and transmitter effectively, and further enhance the signal power. In this article, the M2I in soil environment is studied. Under the ideal condition, COMSOL Multiphysics simulation software is used to establish the two-dimensional axisymmetric magnetic communication transceiver model. The influence of different installation schemes of single-layer metamaterial plate (MP), three-layered composite MP, and bending MP on the induction voltage level at the receiver within 1m distance from the transmitter is studied, and the best installation method is determined. The results show that the MP placed on the front side of the transmitter coil with a gap of 10mm, three-layered composite MP placed on the front side with a gap of 3mm, and a single layer 160° bending plate on the front side of the coil with a gap of 16mm, are the optimal antenna schemes. When comparing the simulation results to other existing systems, it is found that the transmission characteristics are greatly improved. Compared with the traditional MI communication structure, the voltage value at the receiving end of these schemes is increased by 56.6dB, 65.6dB and 86.4dB respectively.