VIGOR+: Energy-Efficient Local Visibility Graph-based Geographic Routing in Large-Scale Sensor Networks

Geographic routing is well suited for point-to-point communication in large-scale wireless sensor networks, because it is a stateless protocol that is, the per-node state is independent of network size. However, the local minimum caused mainly by network holes makes the path stretch increase by up to O(c), where c is the optimal path length. Recently, Tan et. al. proposed a visibility graph-based geographic routing protocol (VIGOR) that bounds the path stretch by a constant. VIGOR scales well, because its per-node state does not depend on network size. However, the scalability and bounded path stretch are possible at the cost of high communication overhead, which makes the employment of the protocol in a practical environment challenging. In this paper, we propose VIGOR+ that reduces the overhead of VIGOR by dividing its visibility graph into subgraphs, each representing the internal structure of a hole in a network; VIGOR+ uses visibility graph-based routing only within each subgraph; the routing outside subgraphs is handled by a novel scheme that uses the convex hull representation of a hole, a much reduced data structure. Through extensive simulations, we show that VIGOR+ has an average path stretch close to 1, while reducing the communication overhead as high as two orders of magnitude in our network configurations.