Cluster-Based Beaconing Process for VANET

In this paper we introduce the Cluster-Based Beacon Dissemination Process (CB-BDP) that aims to provide vehicles with a local vehicle proximity map of their vicinity. Based on this map, safety applications can be used for accident prevention by informing drivers about evolving hazardous situations. The CB-BDP is designed under the two following objectives. First, since it is used for safety applications, we want the map to be detailed and accurate as much as possible. Second, we want the map to be coordinated with nearby vehicles, thereby allowing synchronized and coordinated reactions of nearby vehicles to evolving hazardous situations. We design a cluster based aggregation-dissemination beaconing process that uses an optimized topology to distribute the vehicle proximity map. The topology is adaptive and robust in order to meet the challenging VANET conditions. An accurate and detailed map results in a heavy load of beacon messages. Our proposed scheme deals with this problem by integrating a contention-free medium access control (MAC) strategy for reliable communication. 1 Introduction Vehicular ad hoc network (VANET) is a promising branch of traditional MANET. VANET is designed to provide wireless communication between vehicles and between vehicles and nearby roadside equipment. This communication intends to improve both safety and comfort on the road. The majority of VANET applications require the availability of real-time position information. Some of VANET applications, such as Adaptive Cruise Control and Cooperative Intersection Safety, require a certain degree of positioning accuracy in order to be able to function properly. For new research tendencies and state of the art of VANETs see [37-39]. Critical safety applications though, such as the Vehicle Collision Warning and the Cooperative Awareness applications, which enhance the driver's perception and knowledge of the road and the environment, require very precise and reliable localization system. The acceptable localization error in these applications is with a meter in order to estimate accurately the distances between vehicles and between vehicles and objects. The US FCC has allocated 75 MHz of the spectrum in the 5.9 GHz band for Direct Short Range Communication (DSRC). The DSRC spectrum is divided into seven 10 MHz channels. One of these seven channels is designated as a control channel, and is used primarily for safety related applications. There are two types of traffic safety-related communication that circulate on the control channel: the event-driven messages that are sent whenever a hazard situation has been detected and the periodic beacon messages …