Vehicular Area Networking (VANET) is an emerging technology to support a class of applications involving communications between vehicles, and vehicles and the environment. Activity in this area includes development of the Dedicated Short Range Communication (DSRC) protocol aimed at enabling vehicles to exchange safety information to enhance awareness of the vehicle beyond the line of sight, and to enhance safety features such as active braking and collision warning. While safety is the primary driver for development, additional applications emerge as potential users of this technology that are more general in nature. Real-time traffic and route updates, traffic monitoring, remote diagnostics, general purpose Internet access and in-car entertainment are examples that require data collection and dissemination analogous to the wired Internet. However, DSRC and related short-range communications technology would appear to be insufficient for these scenarios. In this chapter, we describe, how and under what conditions it is feasible, and in fact desirable, to use short range communications. We describe a network formed over moving vehicles implemented by short-range communication and thereby analyze factors that affect the design and performance. Observations reveal intermittent connectivity between vehicles traveling on the roadway in opposite directions that hinders applications. Techniques adapted from related research in computer networks provide solutions for enabling networking in a fragmented network of moving vehicles. We elaborate and demonstrate analytically the application of techniques that enable networking through short-range communication.
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Vehicles are an integral part of urban and suburban life. Mobility of humans, to a large extent, is served by vehicles on land, sea and air. Vehicles serve as instruments in the quest for mobility, cultural exchange and social interaction. As people travel each day, they come into interaction with unique individuals. Vehicles, too, have an opportunity to interact with other unique vehicles. The mobility patterns are often random leading to opportunistic interaction with unique sets of individuals. It has been shown in related work that the opportunistic interaction between different sets can often span the entire network with the passage of time, as is the case with the epidemic spread of news or disease viruses in the human population. Thus, vehicles can be modeled as unique nodes of a network that interact opportunistically, and with sufficient passage of time, span the network.
Our vision for vehicles of the future involves adding communications to all vehicles and connecting them to the larger Internet. Vehicles equipped with communication capability will exchange safety and state information that will allow reactive and proactive systems to warn of potential hazards or mitigate the severity of a collision. Ongoing work exists to develop protocols and standards to allow autonomous communication between vehicles and between vehicles and infrastructure. The US FCC has allocated spectrum in the 5.9 GHz range Dedicated Short Range Communications (DSRC) to allow vehicle-to-vehicle and vehicle-to-infrastructure communication. Our vision for networked automobiles is to enable autonomous control through coordination thereby achieving environmental, economic and societal challenges.
Ad hoc networks formed over moving vehicles, VANETs (vehicular area networks), are a subset of Mobile Ad hoc Networks (MANETs). The network is characterized by fast-paced nodes traveling on constrained paths (roadways) with potentially short-lived connectivity. Vehicles traveling on the vast network of roadways potentially come into contact with many unique vehicles as they cross each other on the roadway. The nature of vehicular mobility presents an interesting challenge to exploit the spatial-temporal correlation of vehicles traveling on the roadway. Vehicles collect statistical travel data as they traverse the roadway. The data are shared with vehicles in the vicinity. The collected data are aggregated and processed to be shared with servers or vehicles outside the immediate neighboring area. The nature of applications in the VANET space has contrasting requirements. Safety-critical applications exist that require very low latency and high reliability. Non-safety-critical, and traffic warning applications have relatively relaxed constraints. Internet access and general purpose data exchange require connectivity to the backbone network that is strongly hierarchical and is a high latency network model.
In this chapter we explore applications that are short-range enabled by multihop communication that exploit the localized nature of information generation and consumption. Observations and analysis highlight the fragmented nature of vehicular connectivity and the potential challenges in enabling vehicular networking. We describe some of the proposed solutions for applications that are localized in nature, especially those where data are generated and consumed in a neighborhood of vehicles connected by multiple hops. We demonstrate that opportunistic contacts in vehicular networks can very well be used to instantiate and sustain certain applications with reasonable assumptions. We summarize the novel concepts of delay tolerant networking (DTN), a connectionless messaging paradigm utilizing opportunistic contacts and intermittent connectivity to forward data.