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Body sensor networks (BSNs) offer a wealth of opportunities for precise, accurate, continuous, and non-invasive sensing of physiological phenomena, but their unique operating environment, the body-area, poses unique technical challenges. Popular communications solutions that utilize 2.4 GHz radio transmission suffer from significant and highly variable path loss in this setting. To compensate for such loss, radio transceivers often transmit at power levels at or above 1 mW-a reality that limits battery life. We propose the use of body-coupled communication to address this issue, as it presents several distinct advantages over existing solutions, namely: reduced power consumption, minimal interference, and increased privacy. In this paper, we demonstrate a 23 MHz body-coupled channel that supports reliable data transfer with an average received power of 30 dBm over a 2.4 GHz radio frequency link. This scheme reduces power needed for transmission and increases battery life by up to 100%, while maintaining a favorable environment for application-specific quality of service requirements. Finally, we propose a system-level hardware architecture and explore its implications on BSN infrastructure.

Abstract-Electronic ratchets transduce local spatial asymmetries into directed currents in the absence of a global drain bias, by rectifying temporal signals that reside far from thermal equilibrium. We show that the absence of a drain bias can provide distinct energy advantages for computation, specifically, reducing static dissipation in a logic circuit. Since the ratchet functions as a gate voltage-controlled current source, it also potentially reduces the dynamic dissipation associated with charging/discharging capacitors. In addition, the unique charging mechanism eliminates timing related constraints on logic inputs, in principle allowing for adiabatic charging. We calculate the ratchet currents in classical and quantum limits, and show how a sequence of ratchets can be cascaded to realize universal Boolean logic.

In this paper, we present a novel computing paradigm using a non-equilibrium electronic ratchet which is capable of driving current in the absence of an applied drain bias. By using a time varying, spatially asymmetric potential, we demonstrate that it is possible to create a net current from drift diffusion processes of charge carriers. This is especially useful in reducing static dissipation encountered in conventional logic circuits. In addition, since the electronic ratchet acts as voltage controlled current source, we find that the dynamic dissipation associated with charging/discharging of load capacitors is also decreased. Furthermore, we show that the ratchet device is naturally amenable to a dissipation reduction technique known as adiabatic clocking. Because of the unique charging mechanism of the ratchet, timing constraints on logic inputs-an important drawback of conventional adiabatic circuits-are not needed to achieve adiabatic computation.

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