The STP design consists of an arrangement of inexpensive
lenses and sensors in the form of an array that gives it a spatial
resolution capability that can be exploited to classify intrusions
while rejecting false alarms arising from clutter. Similar approaches
to STP design have been investigated previously. For
example, in [2], the authors arrange PIR sensors at different
heights along a pole to improve detection accuracy of humans.
However, an important consideration for us was to restrict the
size of the developed STP. Closer placement of the sensors
could effect the spatial resolution capability. We resorted to a
simple but effective trick of off-setting the sensors with respect
to optical axis of their associated lenses. This provision offers
the required spatial resolution while ensuring a smaller platform
size [1].
In addition to the novel STP design, a 3D animation based
simulation tool was developed that helped in quickly evaluating
competing STP designs without the need for physically collecting
data. This helped both for speeding-up the development
process as well as for developing an intuition for the kind of
signals that can be generated by the PIR sensor in response to
various events.
In the later sections, we describe the hardware and software
modules of the PIR sensor-based WSN, requirements for
demonstration and demonstrated system components.