The IG-Ferry Protocol to Support Efficient Controlled Replication in Vehicular Delay Tolerant Network

In the past, we have proposed an intersection graph (IG)-based vehicular ad hoc network (VANET) architecture for efficient unicast communication in the city urban. Thus, the source vehicle can leverage the proposed IG and IG bypass routing protocols to greedily forward unicast packets to the destination vehicle via each intermediate intersection in the calculated least cost IG path. However, when the traffic density is not high enough, there may be several small and disjoint IG graphs in the city. If the source and destination vehicles are not located at the same IG graph, the IG routing protocol fails to find the least cost path between them to forward unicast packets. In this paper, we extend the concept of controlled replication in the Vehicular Delay Tolerant Network (VDTN) to efficiently spray a limited number of packet copies, which is denoted by the value of packet tokens, to three different kinds of relay vehicles, especially the public bus which has a fixed itinerary between the source and destination, with our proposed IG-Ferry protocol and the delay evaluation function. Finally, we conduct NS2 simulations to show that this IG-Ferry protocol outperforms three well-known controlled replication protocols, in turns of average packet delivery ratio and average end-to-end transmission delay of delivered packets.