Vehicular Ad-Hoc Networks (VANETs), a new mobile ad-hoc network technology (MANET), are currently receiving increased attention from manufacturers and researchers. They consist of several mobile vehicles (intelligent vehicles) that can communicate with each other (inter-vehicle communication) or with fixed road equipment (vehicle-infrastructure communication) adopting new wireless communication technologies. The objective of these networks is to improve road safety by warning motorists of any event on the road (accidents, hazards, possible deviations, etc.), and make the time spent on the road more pleasant and less boring (applications deployed to ensure the comfort of the passengers). Practically, VANETs are designed to support the development of Intelligent Transportation Systems (ITS). The latter are seen as one of the technical solutions to transport challenges. This chapter, given the importance of road safety in the majority of developed countries, presents a comprehensive study on the VANET networks, highlighting their main features.
TopIntroduction
The technological advances that the world has experienced today in terms of embedded systems and wireless communication techniques have led man to deal with more and more complex problems. Among these problems, there are the transport problems. In fact, the popularization of vehicles for example has led to problems of safety and efficiency. For that, in a road environment, a transport system is essential to manage road traffic, on the one hand, and develop new applications to improve the comfort of travelers and drivers on the other hand.
Nowadays, several means of transport have appeared, the vehicle is the most common means of transport. This vehicle is increasingly equipped with electronic and computer equipment that has led to the emergence of the term “smart vehicle” or “connected vehicle”. More precisely, a smart vehicle is a vehicle equipped with computers, cameras, network interfaces as well as sensors capable of collecting information and processing it. A set of smart vehicles builds what we call “intelligent transport systems” (ITS) (Figueiredo et al., 2001) (Perallos, Hernandez-Jayo, Zuazola, & Onieva, 2015), which aims to strengthen road safety significantly through safe roads (traffic information, accidents, hazards, possible deviations, etc.) and improve efficiency and user-friendliness in road transport. The architecture on which the Intelligent Transportation Systems (ITS) is based is known as Vehicular Ad-Hoc Network (VANET).
A VANET network (Al-Sultan, Al-Doori, Al-Bayatti, & Zedan, 2014) (Yousefi, Mousavi, & Fathy, 2006) is an emerging technology adopting new communication technologies and wireless devices. Figure 1 shows that the VANETs represent a subclass of MANETs (Mobile Ad-Hoc Networks) (Hoebeke, Moerman, Dhoedt, & Demeester, 2004). A VANET consists of hardware components that include vehicles which are capable to communicate among each other or with fixed equipment from the road based on radio and software components. In other words, a VANET is an ad hoc network characterized by a highly dynamic topology due to the high mobility of vehicles as well as the heterogeneity of their speed and the diversity of their trajectories as a function of road infrastructures. In addition, it is very dense in certain environments such as urban areas. Recently, this type of network has aroused a real interest by research organizations, industrial units and also by cooperation projects because the improvement of road safety has become a government priority in the majority of developed countries.
Figure 1. Hierarchy of wireless networks where the inclusion of VANET in MANET is illustrated
In this first chapter, we will trace the functioning of VANETs through a synthetic description, as we describe their architectures, their characteristics and their various fields of application. We also try to highlight their different issues and challenges where we identify the data dissemination and vehicle location.