Energy-saving wireless sensor node for relative positioning of densely deployed GPS network

Localization of sensor nodes is one of the most essential tasks for sensor network applications for infrastructure monitoring. Normally, the accuracy of global positioning system (GPS) positioning installed in wireless sensor network is in the order of meters (which is insufficient for infrastructure monitoring). This paper developed a GPS wireless sensor network with a capability of onboard GPS analysis based on a relative positioning algorithm with the accuracy in the order of centimeters. However, employment of a high-performance and energy-hungry CPU is inevitable for this onboard GPS analysis method. To reduce the energy consumption, a sensor node called hybrid sensor node equipped with dual CPUs has been developed. A high-performance CPU on the hybrid sensor node is used only for onboard GPS analysis and another CPU with low energy consumption is used for other tasks such as controling of a GPS receiver and a wireless transceiver. This paper describes the design concept, the hardware, and the software of the newly developed hybrid sensor node. The overview of the sensor network system, task allocation, and the performance evaluation of the whole system work flow from the view point of energy consumption are also described in detail.