On Tracking Time with Better Resolution and Range in Batteryless Systems

Accurate and failure-resilient timekeeping is crucial for time-sensitive sensing operations and task scheduling in batteryless systems. The main challenge lies in measuring the duration of power failures precisely. Remanence timekeepers offer a simple and energy-efficient solution by exploiting the discharging characteristics of capacitors to measure the power failure duration. However, existing remanence timekeeping designs in the literature can measure either a shorter power failure duration with a higher resolution or a longer power failure duration with a lower resolution. In this paper, we focus on this trade-off and study how to design an ideal timekeeper offering high measurement resolution and range for batteryless systems. We consider CHRT (cascaded hierarchical remanence timekeeper), the de facto remanence timekeeper for batteryless systems, and improve its design to increase its measurement resolution during longer power failure durations. We evaluate the benefits and trade-offs of our new design. Finally, based on our evaluations, we outline potential improvements and research directions for timekeeping in batteryless systems.