Analysis on channel capacity of magnetic induction based long-distance through-the-earth communication

In order to improve the theory and technology of magnetic induction (MI) based long-distance through-the-earth (TTE) communication, aiming at the weak coupling between transmitter and receiver coils in the MI based long-distance TTE communication scenario, a method for analyzing the channel capacity for long-distance MI-based TTE communication with air coils as antennas of transceivers is presented. Firstly, the magnetic flux density model for TTE communication is established based on the Biot-Savard law and the effect of eddy currents of the earth media. By the equivalent transformation of the transceiver circuits, the received power on the load resistance of the receiver circuit is obtained in consideration of eddy currents. The thermal noise power of the load resistor of the receiver circuit is introduced to determine the channel capacity of the MI-based TTE communication according to Shannon formula. The simulation result shows that the channel capacity of the MI-based TTE communication decreases with the increasing of the TTE communication distance obviously. However, the TTE channel capacity may reach several thousand or hundred bit/s with several hundred meters of TTE distance. It is beneficial to make full use of the limited channel capacity by designing the modulation method of TTE communication properly and meet the requirements for voice and information transmission with long TTE distance.