We have developed a low-power positioning engine with stochastic reasoning and a navigation system that can run even on mobile phones' MPU. The system is robust to signal loss, fluctuation, and noise by analyzing ZigBee wireless packets by stochastic reasoning, and is light weight enough to work even on powerless MPU installed in mobile phones. In addition to positioning, the system provides a functionality of transferring emergency signals using the sensor network only. Users can enjoy navigation services such as shopping guidance in normal circumstances, and once when emergency signal is received, the system automatically switches to emergency mode and provides routing information to the nearest emergency exit.

The system is installed at Landmark Plaza in Minato Mirai area, Yokohama City, and its functionality is verified in an actual building.