An Ultra-Low Power MAC Protocol for In-body Medical Implant Networks

Abstract

We present an ultra low power MAC designed for battery-operated subcutaneous implants. Our MAC protocol addresses special communication needs of medical implants like latency, emergency messaging, priority etc., while maintaining an extremely low power-consumption profile. The paper presents the design choices made for a practical cardiac intra-body network and exploits the inherent asymmetries of the network to reduce power consumption. We present a new scheme for deriving analytically the power-optimised TDMA frame parameters like beacon interval and discuss a hardware solution to manage synchronisation overhead. Equations for deriving the duty-cycling efficiency are presented and the packet error rate is calculated for the in-body wireless channel. Our results and simulations show that our protocol is several times more efficient than the state of the art ultra low power protocols. Thus, we illustrate and validate our solution for a very real use case: cardiac networks. However, our new methodology can be applied for any Body Area Network. In this sense, our paper presents a ‘universal’ solution.