Wireless Sensor Networks by Rastko R. Selmic Vir V. Phoha & Abdul Serwadda

Author:Rastko R. Selmic, Vir V. Phoha & Abdul Serwadda
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

(4.1)

where individual sensors on a node are identified as , . The model considers each node with an equal number of sensors, N, with output values at time instance k given by (i-th sensor on j-th node at time k). A true value of a measured physical variable is and a faulty measurement of the i-th sensor on the j-th node at time instance k is .

Fig. 4.8Model of a WSN that is used in the fault analysis

There are two general categories for fault detection techniques: data-centric and system-centric [37]. Data-centric techniques focus on a single data stream to identify faults, while system-centric techniques consider the whole system to detect faults. The two types of techniques need not be used exclusively. A computationally inexpensive data-centric technique may be used to identify abnormal behavior on a sensor stream, at which point a more expensive system-centric technique can be implemented that compares the sensor data to related neighboring nodes, verifying whether the abnormal data reflects an abnormal environment or a faulty sensor reading.

If a model for the behavior of a measured phenomenon is known, the model can be compared to the readings of a sensor, and the error between the two used for identification of faults. If a model is not known, then other techniques listed in Table 4.2 can be applied to identify faults.

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