UNFOLD: UNiform Fast On-Line boundary Detection for Dynamic 3D Wireless Sensor Networks

A wireless sensor network becomes dynamic if it is monitoring a time-variant event (e. g., expansion of oil spill in ocean). In such applications, on-line boundary detection is a crucial function, as it allows us to track the event variation in a timely fashion. However, the problem becomes very challenging as it demands a highly efficient algorithm to cope with the dynamics introduced by the evolving event. Moreover, as many physical events occupy volumes rather than surfaces (e. g., oil spill again), the algorithm has to work for 3D cases. To this end, we propose UNiform Fast On-L in e boundary Detection (UNFOLD) to tackle the challenge. The essence of UNFOLD is to inverse node coordinates such that a "notched" surface is "unfolded" into a convex one, which in turn reduces boundary detection to simple convexity test. UNFOLD is uniform as every node behaves the same (performing coordinate inversion and convexity test), and it is super fast as both computation and communication involve only one-hop neighbors. We prove the correctness and efficiency of UNFOLD; we also use simulations and implementations to evaluate its performance, which demonstrates that UNFOLD is 100 times more time and energy efficient than the most up-to-date proposal.