Fault and intrusion tolerance of wireless sensor networks

The following three questions should be answered in developing new topology with more powerful ability to tolerate node-failure in wireless sensor network. First, what is node-failure tolerance of topologies? Second, how to evaluate this tolerance ability? Third, which type of topologies is more efficient in tolerating node-failure? Without giving the answers, the existing work regards fault-tolerance topology as the multiply connected graph, and use the connectivity of the graph as the standard to evaluate tolerance ability. In this paper, we argue that fault tolerance of topologies is not equivalent to the connectivity of multiply connected graph by illustrating two concrete examples. Then the definition of node-failure tolerance is presented. According fault and intrusion, the two sources of failure nodes, we define fault tolerance and intrusion tolerance as the standards to evaluate the tolerance ability of topologies, and analyze the tolerance performance of hierarchical structure of wireless sensor network by using these standards. Finally, the function relation between hierarchical topology and its tolerance abilities of fault and intrusion is obtained, and an obvious corollary is that fault tolerance increase with the ratio of cluster head hierarchical structure, but with the intrusion tolerance decreasing.