A Direction-Based Make-Before-Break Routing Protocol for Vehicular Ad Hoc Networks

In this paper, we present a novel ?Make-Before-Break? routing protocol for VANETs (Vehicular Ad Hoc Networks) which brings stability in route even if it contains some nodes moving opposite to the rest. Few of the existing routing protocols contain the mechanism to prevent route disruption caused by link breakages between oppositely moving nodes in a partitioned network. In our protocol, a node does not forward a RREQ (Route Request) received from a node moving in opposite direction unless a special request is made by that node in RREQ packet. The node which accepts this special request and forwards the RREQ, despite moving opposite to the previous node is called complier node. The complier node adds its information in the RREQ packet. On receiving RREQ, the destination knows that complier node is moving towards some successive nodes in the routing path. Through the RREP (Route Reply), it informs those nodes about the complier node. Each of these successive nodes waits for the approaching complier node. When it comes near, each establishes connection with the complier node on its turn. Thus the route from source to destination is maintained. The proposed protocol achieves packet delivery ratio of 85% under very large speed variation condition among vehicles? speed.