Maximizing the capacity of magnetic induction communication for embedded sensor networks in strongly and loosely coupled regions

We attempt to maximize the capacity of magnetic induction communication in strongly and loosely coupled regions. In a strongly coupled region, we investigate frequency splitting, which disturbs the resonance of transmitter and receiver coils. We find a splitting coupling point, which is the value just before frequency splitting occurs, and propose an adaptive frequency-tracking scheme for finding an optimal frequency. The proposed scheme compensates for the degradation of capacity and so guarantees large capacity even at regions where frequency splitting occurs. Next, in a loosely coupled region, we derive an optimal quality factor for maximizing capacity in a two-coil system. As the distance between coils increases, strong resonance is needed to overcome the serious attenuation of signal strength. As a result, the optimal quality factor should be increased. In addition, we find an optimal quality factor for a relay system in order to guarantee reliable communication at long distance. In addition, an optimal-Q scheme that adjusts the optimal quality factor according to a given distance can achieve near-optimal capacity. Finally, through simulations using the Agilent Advanced Design System, we demonstrate the accuracy of our analytic results and the effectiveness of the proposed schemes.