Variability-aware duty cycle scheduling in long running embedded sensing systems

Instance and temperature-dependent leakage power variability is already a significant issue in contemporary embedded processors, and one which is expected to increase in importance with scaling of semiconductor technology. We measure and characterize this leakage power variability in current microprocessors, and show that variability aware duty cycle scheduling produces 7.1× improvement in sensing quality for a desired lifetime. In contrast, pessimistic estimations of power consumption leave 61% of the energy untapped, and datasheet power specifications fail to meet required lifetimes by 14%. Finally, we introduce a duty cycle abstraction for TinyOS that allows applications to explicitly specify lifetime and minimum duty cycle requirements for individual tasks, and dynamically adjusts duty cycle rates so that overall quality of service is maximized in the presence of power variability.