Joint topology control and routing in ad hoc vehicular networks

In mobile networks, particularly in vehicular ad hoc networks (VANETs), the topology is highly dynamic due to the movement of the nodes, hence an on-going session suffers frequent path breaks. Disruption occurs either due to the movement of the intermediate nodes in the path or due to the movement of end nodes, demanding for routing protocols aware of frequent topology changes. In this paper we use the available knowledge about the network's topology to improve the routing protocol's performance through decreasing the probability of path breaks. The topology control identifies long duration links, which are preferentially used for routing. For zones having high density of vehicles, the topology control maintains the oldest links created by the vehicles moving in the same way. For smaller values of vehicles' density, the topology control also uses some of the most recently created links in both moving directions. This choice is shown to increase the routing path duration. The topology control scheme here proposed can be easily integrated in the existent routing protocols: we describe how to integrate it in the Optimized Link-State Routing Protocol. Finally, we compare the performance of our method with the original protocol. Simulation results for scenarios of heterogeneous density of vehicles show that our scheme exhibits better end-to-end path delay and packet delivery ratio than the original routing protocol. This observation is valid for both high and low density of vehicles, being even more evident when the density increases.