International Journal of Computer Applications (0975 – 8887) Volume 92 – No.5, April 2014 31 Study of Routing Protocols for Vehicular Ad hoc Network Jhilam Biswas Department of Electronics & Communication, Manipal Institute of Technology, Manipal Shreya Singh Department of Electronics & Communication, Manipal Institute of Technology, Manipal ABSTRACT The vehicular ad hoc network (VANET) is an emerging new technology. Developing multi-hop routing protocols for urban VANETs is a challenging task. VANETs are a kind of Wireless ad hoc network that usually has a routable networking environment on top of a Link Layer ad hoc network. In this paper, we first analyze the unique features of urban VANET and then we move on to discuss the various VANET routing protocols which already have been proposed. We also analyze and compare the various protocols based on some common parameters. General Terms VANET, routing protocols, metrics of comparison Keywords VANET, DSDV, DSR, AODV, GPSR, MIBR 1. INTRODUCTION Vehicular ad hoc network is a type of MANET [2] (Mobile ad hoc network).It is a technology that uses moving cars as nodes to create a mobile network. VANET turns every participating car into a wireless router to connect. MANET is a self- configuring infrastructure less network of mobile devices connected by wireless. There are various routing protocols which have been suggested in VANET, though not implemented practically. We first start by discussing the proactive and reactive routing protocols, then we go on to discuss the various parameters of comparison. Finally we compare all these protocols based on some common parameters. 2. THE FEASIBILITY OF VANET For VANET routing protocols to work effectively, there should be adequate number of vehicles on the city roads at any given time. Any given vehicle should be within range of at least another one vehicle to establish a link and to prove multi hopping routing practical. 3. BRIEF DESCRIPTION OF THE ROUTING PROTOCOLS IN VANET Based on the available routing theories available in MANET, routing protocols can be broadly sub-divided under two categories- Proactive and Reactive Routing protocols. Destination-Sequenced Distance Vector (DSDV) protocol falls into the proactive ones. It broadcasts message packets periodically and each node maintains the routes to all other nodes in the network. On the contrary, Dynamic Source Routing (DSR) protocol is a typical reactive routing protocol, which sets up the links to form the network only when there is a demand to do so. 3.1 DSDV Routing Protocol In DSDV, each mobile node of an ad hoc network maintains a routing table, which lists all available destinations, the metric and next hop to each destination and a sequence number generated by the destination node. Using such routing table stored in each mobile node, the packets are transmitted between nodes of an ad hoc network. Each node of the ad hoc network updates the routing table with advertisement periodically or when significant new information is available to maintain the consistency of the routing table with the dynamically changing topology of the ad hoc network. 3.2 DSR Routing Protocol DSR provides excellent performance for routing in multi-hop ad hoc. It has a very low routing overhead. It has the ability to deliver almost all originated data packets, even with rapid motion of all nodes. When node P wants to send a packet to node Q, but does not know a route to Q, node P initiates a route discovery. Node P floods Route Request (RREQ). Each RREQ [1] has sender‟s address, destination‟s address and a unique Request ID determined by the sender. Each node appends its own identifier when forwarding RREQ. Every node transmitting the packet is responsible for confirming that the packet has been received by next hop. 3.3 MIBR Routing Protocol MIBR (Mobile Infrastructure Based VANET Routing Protocol) is a location based reactive routing protocol. It‟s a novel protocol which makes full use of the buses, making them a key component in route selecting and packet forwarding. Significant performance improvement in terms of packet delivery ratio and throughput is achieved using MIBR. It estimates the density of each road segment based on the bus line information for road segment selection and prefers buses to ordinary nodes as the forwarding node. The MIBR protocol includes two essential parts: 1) selecting an optimal route which consists of a sequence of road segments with the best estimated transmission quality, and 2) efficiently forwarding packets hop-by-hop through each road segment in the selected route.