Distributed Continuous k Nearest Neighbors Search over Moving Objects on Wireless Sensor Networks

Continuous k -nearest neighbor (C k NN) search is a variation of k NN search that the system persistently reports k nearest moving objects to a user. For example, system continuously returns 3 nearest moving sensors to the user. Many query processing approaches for C k NN search have been proposed in traditional environments. However, the existing client-server approaches for C k NN search are sensitive to the number of moving objects. When the moving objects quickly move, the processing load on the server will be heavy due to the overwhelming data. In this thesis, we propose a distributed C k NN search algorithm (DC k NN) on wireless sensor networks (WSNs) based on the Voronoi diagram. There are four features about DC k NN: (1) each moving object constructs a local Voronoi cell and keeps the local information; (2) in order to keep the reliability of system, the query message will be propagated to related objects; (3) using the idea of safe time, the number of updates is reduced; (4) an equation to estimate a more accurate safe time is provided. Last, we present our findings through intensive experiments and the results validate our proposed approach, DC k NN.