Distributed and dynamic voronoi overlays for coverage detection and distributed hash tables in ad-hoc networks

In this paper we study two important problems - coverage-boundary detection and implementing distributed hash tables in ad-hoc wireless networks. These problems frequently arise in service location and relocation in wireless networks. For the centralized coverage-boundary problem we prove a Ω(n log n) lower bound for n devices. We show that both problems can be effectively reduced to the problem of computing Voronoi overlays, and maintaining these overlays dynamically. Since the computation of Voronoi diagrams requires O(n log n) time, our solution is optimal for the computation of the coverage-boundary. We present efficient distributed algorithms for computing and dynamically maintaining Voronoi overlays, and prove the stability properties for the latter - i.e., if the nodes stop moving, the overlay stabilizes to the correct Voronoi overlay. Finally, we present experimental results in the context of the two selected applications, which validate the performance of our distributed and dynamic algorithms.