Neighbor Knowledge of Mobile Nodes in a Road Network

A key challenge for wireless networks in which nodes can move is for each node to keep track of its dynamically changing set of nearby nodes (neighbors). We present a solution for nodes to maintain neighbor knowledge where nodes communicate via wireless broadcast and are restricted to move on a two-dimensional road network. A road network is a collection of one-dimensional lines that may intersect each other. For nodes to exchange neighbor information, we construct a deterministic collision-free broadcast schedule which utilizes time division multiplexing and geographical segmentation. Under a certain node density requirement and assuming initial neighbor knowledge, our broadcast schedule tolerates node movement on the road network while providing deterministic guarantees in maintaining neighbor knowledge. We also provide a lower bound on the speed of a message propagation given our broadcast schedule. In addition, we consider grouping nodes into clusters and show that, under certain conditions, neighbor knowledge is maintained when two different clusters move close to each other. Finally, we address the issue of obtaining initial neighbor knowledge.