Wireless Sensor and Actuator Networks for Lighting Energy ...

Chapter 5
Autonomous Sensing with Adaptive Sensing Rate
The algorithm of autonomous sensing with adaptive rate is based on prediction
theory and fuzzy logic. It takes advantage of the computational capability of the smart
motes and adds another layer of intelligence to the sensors. Wireless sensor nodes
embedded with the algorithm dynamically adapt their sensing rate to the change of the
physical stimulus, and thus avoid unnecessary sensing and wireless transmission while
retaining high resolution of the overall sensory information for real-time lighting
control purposes.
5.1 Rationale
For wireless sensor networks that monitor phenomena with slow dynamics, it is
sometimes not clear how to set an appropriate sensing rate so that the sensors return
data with good resolution without consuming unnecessary resources by over-sampling.
A fixed or uniform sensing rate that results in good resolution when the system is in
transient state is usually considered unnecessarily high during steady state. High sensing
rates in battery-powered wireless sensor nodes imply that energy is wasted turning the
sensors on/off and processing sensor readings. Although data acquisition generally
requires only a negligible amount of energy in the operation of wireless sensor nodes,
wireless transmission of the acquired readings for real-time control purposes will
contribute to significant power drain. On the other hand, a low uniform sensing rate
could cause an undesirable delay in response to changes even though it consumes less
energy sensing, processing, and communicating as compared to a higher sensing rate.
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