A Passive Geographical Routing Protocol in VANET

In this paper, we present passive geographical routing protocol (PGR), a routing mechanism particularly designed for vehicle ad hoc networks (VANET). PGR has no route discovery phase which is needed by DSR or AODV. In PGR, each node periodically disseminates its location and velocity information along four orthogonal directions of its velocity to distribute routing state in the network. Data packets are first sent in a random direction, and then biased toward the direction according to the received routing state in intermediate nodes. With the nodespsila location and velocity information and assistance of the digital city road map, PSR can prolong the valid duration of routing state stored in the intermediate node. We evaluate PGR with large realistic traffic data in Shanghai. The experiments show that PGR offers a high packet delivery ratio comparing with the traditional routing protocols. The routing overhead is controlled in the network scales as O(n) for N-node networks. This routing scheme has good scalability properties in high dynamic topology of VANET.