| dc.description.abstract | On the road the driver’s primary concern is about the emergency information, for example, traffic jam and car accident. In case that emergency message can be broadcast to drivers as soon as possible, the drivers will have more time to react immediately. However, broadcasting in vehicular ad hoc networks (VANETs) has some problems. The first one is traditional in Mobile Ad Hoc Networks (MANETs): the hidden node and exposed node problem. To avoid this problem that will cause packet collision or delay, the RTS/CTS mechanism is used in MANETs But in VANETs, the vehicle nodes have high mobility and change its environmental location quickly. If using RTS/CTS, it will waste the time to transmit packets. In this paper, we choose only one node to broadcast messages at the same time. The second problem in VANETs is of traffic density. For instance, two nodes cannot exchange packet directly. It lets the rare node does not receive messages. And, we consider this case as low traffic density. In this paper, we forward the messages to the vehicle in opposite lane and Road Side Unit (RSU). We use RSU to improve transmission rate and transmission distance. For deployment of RSU, we also provide a mechanism. Through the average traffic density in the limited time, we can have better results. Finally, we use VanetMobiSim to create node mobilities and put this mobility into NS-2 for simulation. Finally, we have two performance metrics: the transmission time at the same distance and relay count. | en_US |