Virtual Coordinates with Backtracking for Void Traversal in Geographic Routing

Geographical routing protocols have several desirable features for use in ad hoc and sensor networks but are susceptible to voids and localization errors. Virtual coordinate systems which overlay a coordinate system on the nodes offer an alternative that is more resilient to localization errors. However, we show that it is vulnerable to different forms of the void problem where packets reach nodes with no viable next hop in the forwarding set. In addition, it is possible for nodes with the same coordinates to arise at different points in the network in the presence of voids. This paper identifies and analyzes these problems. It also compares several existing routing protocols based on Virtual Coordinate systems. Finally, we propose a routing algorithm that uses geographic routing in the greedy phase and virtual coordinates with backtracking to overcome voids and achieve high connectivity in the greedy phase with higher overall path quality and more resilience to localization errors. We demonstrate these properties using extensive simulation studies.