Advances in the miniaturization of microelectromechanical systems have
led to battery-powered sensor nodes that have sensing, communication and
p- cessingcapabilities. Thesesensornodescanbenetworkedinanadhocmanner to
perform distributed sensing and information processing. Such ad hoc s-
sor networks provide greater fault tolerance and sensing accuracy and
are typically less expensive compared to the alternative of using only a
few large isolated sensors. These networks can also be deployed in
inhospitable terrains or in hostile environments to provide continuous
monitoring and processing capabilities. A typical sensor
networkapplication is inventorytracking in factorywa- houses. A single
sensor node can be attached to each item in the warehouse. These sensor
nodes can then be used for tracking the location of the items as they
are moved within the warehouse. They can also provide information on the
location of nearby items as well as the history of movement of various
items. Once deployed, the sensor network needs very little human interv-
tion and can function autonomously. Another typical application of
sensor networks lies in military situations. Sensor nodes can be
air-dropped behind enemy lines or in inhospitable terrain. These nodes
can self-organize th- selves and provide unattended monitoring of the
deployed area by gathering information about enemy defenses and
equipment, movement of troops, and areas of troop concentration. They
can then relay this information back to a friendly base station for
further processing and decision making. Sensor nodes are typically
characterizedby small form-factor, limited b- tery power, and a small
amount of memory
