Routing and data diffusion in vehicular ad hoc networks
Editor's Note: Wireless sensor networks lie at the heart of emerging applications in nearly every industry segment. In building these networks, designers contend with issues that encompass real-time communications, efficient high-bandwidth data exchange, multiple network topologies, selection of optimal routing strategies, and more. The book, Building Wireless Sensor Networks, offers detailed treatments on critical requirements and promising solutions in each of these areas and more.
This excerpt focuses on design challenges and methods associated with creating a vehicular ad hoc network (VANET). To share data as vehicles pass on roads or rest in parking areas, a VANET must contend with issues as varied as the physics of signal propagation, the fluid nature of data routing, and the security vulnerabilities associated with participation in an ad hoc network. Because of the changing nature of a VANET, designers need a broad understanding of these issues. In this excerpt from the book, the authors offer an in-depth discussion that defines the nature of VANET challenges and discusses alternatives for their solution.
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Adapted from Building Wireless Sensor Networks, by Smain Femmam, Editor.
Chapter 3. Routing and data diffusion in vehicular ad hoc networks
By Frédéric Drouhin and Sébastien Bindel
Data delivery is a crucial task in vehicular networks since current applications require the cooperation of each and every vehicle. Regarding the interaction between the driver and the vehicle, as defined by the National Highway Traffic Safety Administration [NHT 16], a fully autonomous car performs a given driving task under any variety of conditions. Therefore, all decisions taken by the system become crucial, simply because no actual human hand is on the “steering wheel” of the driving system. Information provided by sensors make it possible to construct a local vision of the vehicle; however, the construction of a global vision of the actual situation at hand requires the exchange of information and data. This task is ensured by data delivery services, with the aim of being efficient and reliable. Security aspects must also be taken into account in order to disseminate, receive and process reliable information and data.
The term vehicular ad hoc network (VANET) usually refers to all wireless vehicular networks. Considered as a subset of mobile ad hoc networks (MANET) by [COR 99], VANETs share common features: a dynamic topology due the mobility of nodes, a limited available bandwidth and limited security since the communication medium is shared by all stations. However, vehicles do not have limited energy capacity, because they have an alternator.
Regarding these features, a data delivery service has to ensure reliable communication despite the mobility of nodes, minimize the bandwidth consumption and secure communication. In this chapter, data delivery service in VANET is investigated through three aspects: (i) how to select a destination, (ii) how to route data to a destination and (iii) how to secure communication. The selection of destination is performed through a transmission method, which can reach one or several destinations. In praxis, a special kind of address is assigned to identify nodes such as the unicast, broadcast, multicast or anycast addresses. Data routing is ensured by routing protocols, which determines the path between two non-adjacent vehicles. The computation of the best path relies on information provided by a metric which assesses the “cost” of each path to reach a desired destination. Communication security provides additional services according to the application requirement. Two kinds of security must be considered: passive attacks and active attacks. Within passive attacks, only monitoring tasks are performed, unlike in active attacks wherein an action is performed by a hacker.
The remainder of this chapter is organized as follows. Section 3.2 describes the context and challenges related to each considered aspect of the data delivery service. In section 3.3, routing protocols related to vehicular networks are detailed. In section 3.4, security aspects are detailed. Section 3.5 closes this chapter and provides outlook.
3.2. Background and challenges
The deployment of routing and security solutions requires compliance with the characteristics and standards of vehicular networks. Regarding the features of VANET, the high dynamic of the topology and the uncertain and random density of vehicles have a significant impact on the connectivity to the network and the delivery delay. Information provided by on-board sensors gives local information, such as the position, useful for commutation. Communications in vehicular networks rely on three architectures. The first one is the Vehicle-to-Vehicle ad hoc network (V2V) where vehicles communicate directly to each other and form a fully distributed network. The second one is the Vehicle-to-Infrastructure network (V2I) wherein vehicles communicate only with the roadside infrastructure via RoadSite Units (RSU) and form a centralized network. The last one is the hybrid architecture combining both the V2V and V2I infrastructures. A vehicle can communicate either in a single hop or multi-hop fashion. The design of routing and security solutions needs to take into account the network architecture, the communication standards defining the protocol stack, and the signal propagation to understand the disturbances generated by the environment.