The objective of this thesis is to detect malfunctioning sensors in wireless sensor networks. The ability to detect abnormality is critical to the security of any sensor network. However, the ability to detect a faulty wireless sensor is not trivial. Controlled repeatable experiments are difficult in wireless channels. A Redhat Linux. 7.0 Wireless Emulation Dynamic Switch software was used to solve this problem.
Six nodes were configured with a node acting as a base station. The nodes were all part of a cell. This means that every node could communicate with all other nodes. A client-server program simulated the background traffic. Another program simulated a faulty node. A node was isolated as the faulty node while all other nodes were good. The experiment ran for several hours and the data was captured with tcpdump. The data was analyzed to conclusions based on a statistical comparison of good node versus bad node.
The statistical delay on the good node was an average of 0.69 ms while the standard deviation was 0.49. This was much better than the delay on the bad node that was 0.225192 s with a standard deviation of 0.89. This huge difference in the delay indicated that the faulty node was detected statistically. A threshold value of I ms was chosen. The good node was within this value about 98% of the time. The bad node on the other hand was far out of this range and was definitely detected. The channel utilization data provided the same conclusion.
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