Hierarchical and Scalable Routing in Infrastructure-based Vehicular Networks

Vehicular delay tolerant networks (VDTNs), as a special type of vehicular networks, there is no end-to-end path exists between vehicle nodes. In this paper, a novel and scalable landmark-based forwarding method named Two-Layer Vehicular Delay Tolerant Routing (TLVDTR) is introduced that routes messages between regions and landmarks instead of performing routing between nodes. This method maps the network to a two-layer model. At the upper layer, the network operation area is divided to some regions by using the edge betweenness centrality and in the lower layer; a network of landmarks is organized to track vehicles' movement between popular places. Then, each Landmark finds the shortest path to other landmarks in its region and constructs an inter-landmark routing table. After that, by exploiting a distance vector algorithm and advertising routes mechanism, the routing table will be extended to store routes to landmarks of other regions. Beside the network structure organization, probabilities of transition between landmarks are computed by using nodes historical movement trajectory. Finally, by using both routing table and transition probabilities, our proposed method can select the suitable relays for carrying messages toward target landmarks. The evaluation results show the superiority of our proposed method in terms of delivering ratio (16%), average delay (17%) and forwarding cost (4%).