A comparative study of Broadcasting Protocols in VANET

I. I.INTRODUCTION Work on the ad hoc network begins from 1970s when network were originally called packet radio networks. Inter-vehicle communications (IVC) and Roadside-to-Vehicle communication (RVC) are becoming one of the most popular research topics in wireless communications. Capability of VANET has to provide safety and traffic management: vehicles can notify other vehicles of hazardous road conditions, traffic jamming, or rapid stops [5]. VANET is formed by vehicles with wireless equipment for communication. It allows vehicles to communicate directly to each other without infrastructure deployment. VANET is one of the special forms of mobile ad hoc networks (MANET), which gains interest from many researchers. But VANETs are different from MANETs in several ways. First, vehicles are in large volume, and network topology changes rapidly. Second, the mobility of vehicles is constrained by roads with limitations on driving speed. Although vehicles can move in high speed, their directions and speeds are predictable. Third, vehicles usually do not have tight energy budget. Instead, bandwidth issues are more critical than energy ones in VANETs [5] [7]. VANET brings up the communication solution instead of relying on infrastructure to be ready. So most of applications in Intelligent Transportation System [2] can exchange information directly with less delay. To achieve this, communication protocols must cope with the mobility of vehicles and the dynamics of wireless signals. Broadcasting is the task of sending a message from a source node to all other nodes in the network. The two major challenges of broadcast are to ensure the reliability of messages while disseminating message over the intended regions and keeping the delay time within the requirements of the application. The design of reliable and efficient broadcast protocols is a key enabler for successful deployment of vehicular communication services. To design a reliable and efficient broadcast protocols. One should take the following metrics into considerations. The first metric is reliability; that is, a broadcast message should deliver to as many vehicles as possible. Second metric is overhead; that is, delivery of the broadcast message to all vehicles should generate as few redundant messages as possible. The last metric is speed of the data; that is, a broadcast message should be delivered to all vehicles as fast as possible. Although a broadcast message can reach all vehicles, it can be meaningless if it arrives too late. This metric is very critical for emergency services. In VANET, several reliable broadcasting protocols have been proposed such as DBR, ABBR and STREETCAST. The details of each protocol will be discussed in further. In this paper, we compare these reliable broadcasting protocols on VANET. We then evaluate the reliable broadcasting protocols in terms of reliability, overhead and speed of data by simulation. Our simulation results show problems on each protocol [6]. ABSTRACT: Vehicular Ad-hoc Network (VANET) represents a challenging class of mobile ad-hoc networks that enables vehicles to intelligently communicate with each other and with roadside infrastructure. Reliable and efficient broadcasting in vehicular ad hoc networks is one of the keys to success for services and applications on intelligent transportation system. Many protocols have been introduced but none of them has been evaluated in realistic scenario. In this research, we discuss the reliable broadcasting protocols such as Distance Based Routing (DBR), Street cast and Acknowledgement-Based Broadcasting Protocols (ABBP) on VANET. Then, we evaluate performance of these protocols by simulation. From simulation result, we found a performance and problem in each protocol, which can lead to broadcast storm problem and inefficient operation.