No abstract

Vehicular Ad hoc NETworks (VANETs) have emerged as a platform to support intelligent inter-vehicle communication and improve traffic safety and performance. The road-constrained, high mobility of vehicles, their unbounded power source, and the emergence of roadside wireless infrastructures make VANETs a challenging research topic. A key to the development of protocols for inter-vehicle communication and services lies in the knowledge of the topological characteristics of the VANET communication graph. This paper explores the dynamics of VANETs in urban environments and investigates the impact of these findings in the design of VANET routing protocols. Using both real and realistic mobility traces, we study the networking shape of VANETs under different transmission and market penetration ranges. Given that a number of RSUs have to be deployed for disseminating information to vehicles in an urban area, we also study their impact on vehicular connectivity. Through extensive simulations we investigate the performance of VANET routing protocols by exploiting the knowledge of VANET graphs analysis.

No abstract

IntroductionWith the recent development of technologies in wireless access and mobile devices, the mobile network has become a key component of today's Internet vision [1,46]. Current mobile networks, which are being deployed worldwide, enable mobility features to new applications and also extend existing wired Web applications to mobile terminals. The mobile wireless network offers a rich assortment of dynamic and interactive services, such as GPS navigation information, mobile TV, vehicular traffic information, and location-oriented services. The provision of such services requires techniques to disseminate data as efficiently as possible in order to minimize the total network traffic and to improve the mean response time to mobile users.In the wired Web, network performance can be substantially enhanced by using additional bandwidth, which is often available at low cost. However, this approach is impractical for mobile wireless network infrastructures. Most of these networks have fixed spectrum and achievable data rate is fundamentally limited by interference [46]. This problem is likely to get more serious when more mobile users start using bandwidth-intensive services such as streaming media. In this context, caching and prefetching might be a solution. Specifically, these approaches have been extensively used in the wired Web to optimize the amount of bandwidth consumption by shifting the traffic away from overloaded content providers and closer to the content customers [43]. Although these methods offer several benefits (i.e. conservation of network resources and reduced latency), the dissemination of dynamic content and resource-hungry applications (e.g. multimedia applications) remain a challenge. Content Delivery Networks (CDNs) promise to address these challenges by moving the content to the "edge" of the Internet, and thus closer to the end-user [45]. An introduction to CDNs can be found in the first chapters of this book. Although there has been much work on wired CDNs [27,32,40], content dissemination on mobile environments has received little attention so far [1,49]. This is due to the limited Internet access capabilities of most mobile terminals in the recent past. However, this situation seems to be changing with the advent of innovative cellular (e.g. 3G) and wireless (e.g. WiFi) services which allow mobile terminals to access Internet and other data services at speeds comparable to traditional wired access [46]. Previous research [6,48] shows that cooperative caching in mobile environment improves the network performance and information dissemination. In this context, we believe that the infrastructure of CDNs may provide a scalable and cost-effective mechanism for accelerating the information dissemination in the mobile wireless environment [45]. However, the mobile wireless network infrastructure represents a fundamentally different information medium from the traditional Web in terms of access devices used, content availability, bandwidth, and cost to the end-user. Thus, the typical CDNs can...

No abstract