Full-Wireless Field Monitoring Server for Advanced Sensor-network

Field Server (FS) is a rugged server which can be installed in fields. Field Monitoring Server (FMS) is a kind of FS for monitoring. So far, solar cell embedded on the top of FMSs have been used only as a light intensity sensors. The power source for FMS is supplied by a cable, since the solar cell's power alone is not sufficient to run conventional FMSs. To construct a massively distributed monitoring system by using wireless sensor network in fields especially in paddy fields, a power supply cable is obstructive. We developed power-saving technologies so that the solar cell can drive the FMS. New network architecture was developed which combined access-point (hotspot), ad-hoc network among access-points (repeating mode) and client connection to access-point. Conventional wired FMSs function as a backbone by using an ad-hoc network, where power is usually supplied by cable or larger solar cell. Simultaneously, the conventional FMSs provide a hotspot, where residents, gussets and full-wireless FMSs also can connect to the Internet by client connection. Energy consumption of full-wireless FMSs is half that of conventional FMSs. Yet energy consumption must be reduced up to 1/200-1/1000 for embedded solar cell to drive the FMS. Sleep mode also is introduced, and FMS is switched off immediately after the Fieldserver-agent collects data.