In past few years the communication between vehicles has gained a lot of importance. Vehicular Ad-hoc Network (VANET) is derived from Mobile Ad-Hoc Networks (MANET) which is a best approach for the vehicle to vehicle communication. The existing routing protocols of MANETS are not effectively applied in VANETs. Therefore, VANET supports a few routing protocols, and their performance is evaluated using simulation studies. In this paper, we mainly compare the performance of routing protocol such as DSDV, OLSR and AODV in VANETs using ns-3 simulation tool. With the consideration of parameters such as throughput, packet delivery ratio and overhead the performance of routing protocols for VANETs are discussed. The key challenge is to find the best routing protocol for VANET in both Grid and Random fashion by comparing the above mentioned parameters. The simulation results shows that the nodes arranged in Grid fashion has better communication among them compared to the nodes arranged in Random fashion. Keywords: Mobile ad-hoc network (MANET), Vehicular ad-hoc network (VANET), Routing protocols, ns-3 tool.
I. INTRODUCTION [1]An ad hoc network is a wireless system of mobile nodes that cooperatively form a network. Every node in ad hoc network is responsible in routing information between its neighbours. When these nodes are free to move randomly and organize themselves arbitrarily we refer this as Mobile Ad Hoc Network (MANET). The evolution of traditional MANET is VANET. Vehicular ad-hoc networks (VANET) are created by applying the principles of mobile ad-hoc network (MANET) [7].VANET includes communication between moving vehicles on the roads. It is a special application of mobile ad-hoc network. This application is further divided into two classes. One class focuses on security application which is mainly used to solve traffic safety and the other is user application which is used to provide value added service. To improvise the safety of drivers and provide secure and comfortable driving environment, intervehicular communication is necessary to communicate through the message for different purposes. Destination Sequenced Distance Vector routing protocol (DSDV)[5] is a table-driven routing scheme for ad-hoc mobile networks based on Bellman-Ford algorithm. The main contribution of the algorithm was to solve the routing loop problem.[12]The Optimized Link State Routing protocol (OLSR) [3] is a proactive link-state routing protocol, which uses hello and topology control (TC) messages to discover and then disseminate link state information through the mobile ad-hoc network. Ad-hoc On-Demand Distance Vector (AODV) [3] protocol establishes routes to destination on demand and supports both unicast and multicast routing.