Wireless Mesh Networking with Mother Nature

Wireless mesh networking technology, much reported on for its potential contributions to military operations and homeland security, is also at work in a nature preserve. Some of Crossbow?s MICA2 family of wireless sensors have been deployed about the James Reserve in the mountains east of Los Angeles.

Under the auspices of the Center for Embedded Network Sensing (CENS) at UCLA, a microclimate monitoring project is under way as part of a program of ecophysiological studies. The first generation of this Extensible Sensing System (ESS) consists of MICA2 motes with an environmental sensor board developed by Crossbow and Mohamman Rahimi on the CENS staff. Each sensor node (MICA2 and MDA300CA combination) is responsible for gathering certain climate-related sensor data including temperature, leaf wetness, soil moisture, and wind speed and direction. The nodes collect information through a multihop mesh network into multiple head nodes. Each head node is a Crossbow Stargate Gateway running a data logging and networking stack under Linux. The overall ESS data collection and aggregation software, written and tested by researchers on the CENS team, is one of the first wireless sensor networks to be deployed on the scale of hundreds of nodes.

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The nodes transmit their data to a single cluster head. Each node is able to choose the cluster head to which it forwards its data. The node can also determine how many hops away it is from each cluster head so it can make the appropriate choice. Every node sends its local adjacency list and link statistics to the cluster head it selects, and also reports on its battery voltage as an indication of its health.

The sensor nodes, the Stargate cluster, and nodes in the ESS are powered by a combination of solar panels and deep-cycle batteries. The system can log and transmit core small-scale environmental data to a central facility, and use analog and digital data inputs for controlling microvideo cameras and proximity sensors. Environmental data are transmitted via the Internet back to the UCLA campus.

Contact Melissa Horton, Crossbow Technology, Inc., San Jose, CA; 408-965-3306, [email protected].

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