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

Abstract

Vehicular Ad Hoc Networks (VANETs) have become a hot topic of research nowadays. Besides numerous safety applications, many entertainment applications of VANETs are being proposed. Dedicated data communication between two vehicles on the road requires a fixed multi-hop route between them. Extremely high mobility of vehicles on highways makes the task of providing stable route very challenging. Sometimes when node density is not high, a VANET may get partitioned. Including some nodes moving opposite to the source and destination in routing path becomes indispensable in this case. However links between oppositely moving nodes break more quickly. Many existing reactive routing protocols attempt to achieve route stability by employing selectivity during route setup. Few of them contain the mechanism to prevent route disruption caused by link breakages between oppositely moving nodes in the route. In this thesis, we present a novel “Make-Before-Break” routing protocol which brings stability in route even if it contains some nodes moving opposite to the rest. A node does not forward a route request (RREQ) received from a node moving in opposite direction unless a special request is made by that node in RREQ packet. The special request is made by a node if it finds that it has no neighbours moving in the same direction in which it is heading. The next node, called Complier, which forwards the RREQ despite moving opposite to the previous node, puts 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 route reply (RREP), 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 % in presence of very large speed variation among vehicles’ speed.