Normally-off power management for sensor nodes of global navigation satellite system

Global Navigation Satellite System (GNSS) is a well known method to detect the location. A GNSS sensor is integrated with wireless sensor nodes to know its location distributed in geographically wide area, along with some energy harvesting device such as a solar cell. However, the GNSS sensor consumes relatively larger energy and requires longer sensing time for tracing satellites everytime, compared with other sensors. Although some power-down modes are used to reduce the power consumption, such as a "sleep-mode" and a "standby-mode", accumulation of running time and waiting time power is not small enough for a smaller capacity solar cell. "Normally-off" is a way of computing control which aggressively powers off components of computer systems. It uses power gating mechanisms and nonvolatile memories (NVMs) to turn off the power supply component by component. We applied the Normally-off control to a wireless sensor node to achieve extra low power for a smaller solar cell. This paper describes our Normally-off Computing application to the GNSS aware sensor nodes and evaluation of the performance under solar cell power supply.