Trap Coverage for Mobile Targets

Tracking of movements such as that of people, animals, vehicles, or of phenomena such as fire, can be achieved by deploying a wireless sensor network. So far only prototype systems have been deployed and hence the issue of scale has not become as critical. Real-life deployments, however, will be at large-scale and achieving this scale will become prohibitively expensive if we require every point in the region to be covered (i.e., full coverage), as has been the case in prototype deployments. We therefore, propose a new mode of coverage called Trap Coverage that scales well with large deployment regions. A sensor network providing Trap Coverage guarantees that any moving object or phenomena can move only a (known) bounded displacement before it is guaranteed to be detected by the network for any trajectory and speed. Tracking applications aside, the model of trap coverage generalizes the de-facto model of full coverage itself, by allowing for holes of a given maximum diameter. We have taken first steps toward establishing a strong foundation for this new model of coverage by addressing some fundamental problems. We show by simulations that our analytical predictions of density are quite accurate even for small networks. We have proposed a polynomial-time algorithm to determine the level of trap coverage achieved once sensors are deployed on the ground.

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