Opportunistic Broadcasts in Vehicular Networks

Abstract

In this chapter, we apply the concept of opportunistic routing in broadcasts in vehicular networks. Vehicular ad hoc network (VANET) is a special type of mobile MWN designed to provide a wide range of road applications such as safety warning (Torrent-Moreno et al. 2009;Xu et al. 2004), congestion avoidance or mobile infotainment (Li et al. 2011). One important function of VANET is the broadcast of event-driven warning messages (WMs) like accident and hazard warning, for example, after two vehicles collided with each other on a highway, or traffic congestion happens because of heavy rain or snow, the upcoming vehicles need to be notified immediately. In both cases, the WMs should be disseminated with only a short delay to vehicles that are up to several kilometers away, not only to prevent more possible accidents but also to enable the vehicles to make a detour as early as possible to avoid congestion. While Dedicated Short Range Communication (DSRC) (http://www.standards.its.dot.gov/Documents/advisories/dsrc advisory.htm) allows the data transmission range of vehicles to be up to a few hundred meters, a single-hop broadcast is not sufficient to provide the desired warning message coverage. So a multihop broadcast is necessary to disseminate time-sensitive warning messages in VANETs.There are three main performance goals in WM broadcast in VANETs. 1. High reliability, which is usually measured as the percentage of vehicles that received the warning message. 2. Fast dissemination-that is the warning messages should be delivered to the vehicles with short end-to-end delay. 3. High scalability, which means the WM's propagation should only incur a small transmission overhead (especially when the network is dense) because unnecessary transmissions waste Multihop Wireless Networks: Opportunistic Routing, First Edition.