Battery-Aware Embedded GPS Receiver Node

This paper discusses the design and implementation of an ultra low power embedded GPS receiver node for use in remote monitoring situations where battery life is of the utmost importance. The power consumed by a GPS radio is high when compared to other typical components of sensor networks. We offer several hardware and software solutions to prolong the battery life while preserving a required GPS tracking precision. A standard SiRF trickle mode, available on some of the latest chipsets switches between the full power and a single fixed duty cycle. If the fixed duty cycle is set too low, trickle mode causes too many signal drops; if set too high, consumes too much energy. Adding a low-power microcontroller allows us to dynamically change the operation mode by setting the duty cycle in relatively small steps, based on a set of less stringent and application dependant set of rules. In addition, an accelerometer is used as an energy efficient way of detecting that the object or person carrying the GPS is not moving. This allows the GPS-equipped node to switch to the lowest possible power consumption mode that still allows for fast restarts. Several hardware and software design aspects are explored and several measurements comparing system performance to commercially available products are shown to illustrate the effectiveness of the system.