Reliability and fault tolerance of coverage models for sensor networks

We study the coverage problem for sensor networks from the fault tolerance and reliability point of view. Fault tolerance is a critical issue for sensors deployed in places where they are not easily replaceable, repairable and rechargeable. Failure of one node should not incapacitate the entire network. We propose three 1-fault tolerant topologies, namely square, hexagonal and improved 8-node. We show how to extend these to k-fault tolerant schemes and calculate reliabilities using Markov models. The proposed models are compared to one another, as well as with the minimal coverage model of Zhang and Hou. The minimum coverage model is the most unreliable among the models, whereas the improved 8-node model is the most reliable except at the very beginning of the system, where the square model is more reliable. To our knowledge, this is the first paper which studies a pattern from the perspective of reliability.