RoHR: Regionalized Hierarchical Routing for Vehicular Networks

Vehicular ad hoc networks (vanet) are composed by mobile nodes that are vehicles. They face difficulties in maintaining communications due to their dynamic topology, where routes are frequently broken as communicating nodes move apart. Geographic routing protocols, particularly those based on clusters are frequently employed to mitigate this problem. However, they are not suited to the special characteristics of urban environments. Aiming at a better performance for this kind of environment, this work proposes the Regionalized Hierarchical Routing (RoHR) protocol. In this protocol, the network topology control is based on clusters, composed by sets of vehicles located within delimited regions, denominated sectors. The position of each cluster-head (CH) is fixed within each sector. Each vehicle is associated with a cluster, depending on its position. Each CH knows the positions of its members. The organization of clusters is hierarchical, since a set of adjacent clusters forms a new top-level cluster. Data transmissions over long distances are carried out by multiple hops, using greedy geographic routing. CHs are used to query the position of the vehicle to which the communication is addressed. All the communications are V2V (vehicle to vehicle), RoHR do not use infrastructure. Each vehicle are aware of its own position, the position of the CH to which it is associated and the map of sectors. RoHR was compared with the canonical AODV (Ad-hoc On-demand Distance Vector) protocol, presenting a superior performance in terms of end-to-end latency.