Galvanic Coupled Intra-body Communication Technology
Implanted sensors will drive the next generation of personalized medicine with in-situ monitoring of abnormal physiological conditions using implanted sensors, and proactive drug delivery using embedded actuators. Autonomous and direct communication among implants through the body tissues is crucial for realization of the above vision, which we achieve using galvanic coupling of weak modulated electrical signals. This new communication paradigm involves several interesting challenges, including (i) signal propagation characterization of different tissue paths and (ii) identifying the best placements of implants and relays towards extended implant life. we systematically analyze the channel between implanted scenarios (e.g., sensor on skin and actuator in muscle) using suite of equivalent circuit model for three dimensional human arm with four tissue layers - outer dry skin, fat, muscle and bone. Each tissue is modeled using four impedance based on the current paths for various sensor separations, tissue dimensions, hydration levels, operating frequency, noise, and electrode specifications. The results are verified with finite element human arm simulations and empirical measurements using porcine tissue.
Using the channel characters thus obtained, the basic link budget is computed including the channel bandwidth, capacity, quantity of implants that can be accommodated and their life expectancy. Towards the topology formation, we then devise energy efficient relay placement strategy and show that the proposed technique extends the implant life by years. Maturity in galvanic coupled intra body communication with suitable physical layer and medium access protocols will potentially revolutionize health care with diverse applications arising out of a network of connected implants.