Abstract
Recently, vehicular ad-hoc networks become an interesting research area due to safety-purpose applications, such as collision avoidance system. In such applications, emergency message dissemination is one of the most important issues because shorter transmission time can advance driver’s response time. Previous protocols proposed for emergency message dissemination only consider either shortening transmission latency or minimizing packet overhead. In addition, we find that in real applications the usability of emergency messages will degrade with time and transmitted distance from events. Therefore, we propose an efficient emergency message dissemination scheme whose goal is to minimize the transmission latency and low packet overhead. Considering the usability of emergency message, we define two regions; emergency region and alarm region, where emergency region is close to emergency events and alarm region is close to the previous ramp closest to these events. Then emergency message with a predefined life time will be kept in these two regions. So, only vehicles entering into these two regions can receive emergency messages. Simulation results show that the proposed scheme can reduce the transmission latency immensely comparing with previous works. Furthermore, we keep an emergency message for a critical time interval with low packet overhead.