VANETs Networking Protocols: An Analytical Study Samira Harrabi ENSI University Mannouba, Tunisia Email: samira.harrabi@gmail.com Ines Ben Jaffar ESCT University Mannouba,Tunisia Email: ines.benjaafar@gmail.com Khaled Ghedira ISG University Tunis, Tunisia Email: khaled.ghedira@anpr.tn Abstract—Vehicular Ad hoc NETworks (VANETs) are considered as a class of Mobile Ad hoc NETworks (MANETs). The VANETs are a set of vehicles that are capable of exchanging data dynamically and without needing any pre-existing and fixed network infrastructure. Each node sends and receives messages in its communication area. Thus, message routing is done through a routing protocol. Despite the fact that the VANETs are a subgroup of the MANETs, they possess exceptional network behaviors like high mobility and dynamic topology, which make the MANETs routing protocols unsuitable for the VANETs. This paper summarizes the different protocols used for routing in the VANETs that focuses on a vehicle-to-vehicle communication. Utilizing an OMNET++ simulator, the experimental results are discussed to compare the presented routing protocol categories. Keywords–VANET; Routing protocols; OMNET++. I. I NTRODUCTION A Vehicular Ad hoc NETwork (VANET) is a commu- nication network between vehicles equipped with comput- ers, network devices and various types of sensors [1]. In the VANET, vehicles communicate with each other via a Vehicle-to-Vehicle (V2V) communication and with the road- side through a Vehicle-to-Infrastructure (V2I) communication. Fig. 1 shows an example of the VANET. Figure 1. Example of VANET scenario. Even though the VANET is a subclass of a Mobile Ad-hoc NETwork (MANET), it has specific network characteristics, as follows [2]: • High mobility The VANETs are characterized by a high mobility of vehicles. Therefore, a node may join or leave the network in a very short time, which makes a very frequent change of the topology. In addition, routing problems can occur when communication links are broken suddenly due to an important velocity value, i.e., an intermittent connectivity problem. • Communication environment The environments considered by the VANET are often un- favorable particularly in urban areas. Vehicle movements are related to road structures (intersections, traffic signs, etc.) and road base stations (infrastructure) in highways or within a metropolitan area. The constraints imposed by this type of environment, such as radio obstacles and impacts of multipath propagation, affect the quality of services as well as radio transmissions. • Constraint of energy Unlike the MANET, where the energy constraint is an addressed challenge issue, the VANETs energy is not a critical behavior because the components of the VANET have no limit in terms of energy and may have multiple communication interfaces. • Density Variation The density of nodes in the VANET is not uniform. For example, in an urban environment the density is much higher than in rural areas. The number of vehicles in an intersection or in a traffic jam is more important than in another area where traffic is often fluid. In addition, the density is different depending on the night or the day, and / or peak or break hours. This density diversity makes it difficult to design routing protocols. • Network partitioning This problem mainly occurs when the node density is low. Then, the vehicles move in isolated and non-connected groups. Therefore, it becomes difficult in this case to ensure end-to-end communications. From the above characteristics, it is evident that designing a suitable routing protocol for the VANET is a big challenge. In addition, the presented behaviors make the MANET routing algorithms unsuitable for the VANET [3]. Hence, routing in the VANET has been the subject of many research works and several protocols have been proposed [4][5][7][8][9][10]. Based on the path creation manner, as well as the maintenance of routes, we can classify the VANET routing protocols into two major categories: hierarchical and non-hierarchical protocols. The aim of this paper is to study the impact of the 1 Copyright (c) IARIA, 2016. ISBN: 978-1-61208-490-9 SENSORCOMM 2016 : The Tenth International Conference on Sensor Technologies and Applications