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strate the concept), such a network would be required to last for months, if
not years. This motivated us to investigate the various power management
schemes that can be used to extend the lifetime of the ExScal network from
three days to several months, without deploying redundant sensor nodes or redundant
batteries per node (keeping in mind the cost minimization objective
of ExScal).
3.1 The XSM Platform
The XSM (Extreme Scale Mote) [9] is a sensor platform developed for the
ExScal project. It was a refinement of the Mica 2 platform [7]. Its design was
optimized for use in intrusion detection applications. Figure 2 shows an XSM
deployed on the ground in its usual enclosure. The XSM had three types
of sensor ??” a 2-axis Magnetometer to detect ferrous materials, a Passive
Infrared (PIR) to detect motion, and an Acoustic sensor to detect objects
making sounds (e.g., vehicles). Figure 3 shows the circuit board of an XSM.
The sensing ranges for these sensors for various types of objects appear in
Table 1.
Fig. 2. An XSM (Extreme Scale Mote) deployed on the ground in its usual enclosure
during the ExScal demonstration.
The current consumption of the major components of XSM appear in
Table 2. We use mA (milliamperes) for the unit of current consumption. The
amount of energy consumed by a component will depend on the amount of
time that it is used.
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Fig. 3. Inside an XSM.
Table 1. Sensing ranges (in meters) of the three sensors used in the ExScal project.
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