Post data-collection synchronization for approximation of simultaneous data

Abstract

A system for synchronizing data after they are collected and stored locally in sensor units in a distributed sensor system, so that wired or wireless communication is not required during a data-collection session. Each sensor unit has a local clock providing local-clock times before and after a data-collection session, and a data processor uses its local clock or a sensor unit's local clock as the reference to compute each sensor unit's time-scaling factor, which is the ratio of the elapsed reference local-clock time and the elapsed local-clock time. The data processor uses the time-scaling factor to convert each sensor unit's local-clock data-sampling times to the reference local-clock data-sampling times, and the data processor subsequently interpolates sensor data to approximate simultaneous sensor-data values at desired reference local-clock times. A physical-activity monitoring system can use this synchronization method to reduce the size, power consumption, and cost of the sensor units.