Channel characteristics of long-distance magnetic induction based through-the-earth communication and performance analysis

Magnetic induction (MI) based through-the-earth (TTE) communication has low path loss, no multipath effect and stable transmission channel. The generation and propagation of magnetic fields in MI-TTE communication do not have the strict requirements of antenna size than that in electromagnetic wave based TTE communication, which is conducive to achieving bidirectional communication between the ground and underground. An equivalent circuit of the receiving and transmitting circuit has been established for long-distance MI-TTE communication, and the transmission function of MI-TTE communication channel can be characterized using the equivalent circuit of the receiving and transmitting circuit. The noise of receivers of MI-TTE communication mainly includes thermal noise on the receiving circuit and electromagnetic noise in the environment where the receiving coil is located. The noise characteristics of receivers of MI-TTE communication were analyzed. The channel characteristics of MI-TTE communication such as amplitude frequency response, impulse response and bandwidth were analyzed by simulation under different TTE medium parameters and TTE communication distance. The amplitude spectrum of the received signal was compared with the amplitude spectrum of the noise. A simulation platform of MI-TTE communication was built, and the performance with BPSK and QPSK modulation was compared under different TTE medium parameters and TTE communication distance. The maximum modulation order that can be adopted by MI-TTE communication under different TTE medium parameters and TTE communication distance was given. These play an important role in improving the performance of long-distance MI-TTE communication systems.