Wireless Sensor and Actuator Networks for Lighting Energy ...

Figure 5-1 Mechanism for adaptive sampling [93].
5.2 Algorithm and Mathematical Detail
The algorithm developed follows the idea in [93] and [94] with a better choice
of predictive model and adaptive rules. The architecture of the algorithm is shown in
Figure 5-2. In each iteration, before a sensor reading becomes available the predictive
model generates a one-step prediction of the incoming sensor reading yk ˆ( ), which is
compared to the actual sensor reading y(k) to calculate the prediction error e(k) as in
(5.1). The parameter of the predictive model is updated according to e(k) for predicting
the next incoming sensor reading yk+ ˆ( 1) . Meanwhile, the prediction error serves as an
index of how fast the environment is changing so that the fuzzy sensing rate adaptor can
adjust the sensing rate to ensure the resolution of the sensed information.
e(k) = y(k) ŷ(k) (5.1)
Figure 5-2 Architecture of adaptive sensing rate algorithm.
63