The Research Of Broadcast Protocols For Emergency Messages In VANETs

In recent years VANETs has been widely researched at home and abroad. Security application, as one of its most important applications, attracts more attention. During the moving process of vehicles, they may encounter in road which has complex geometric properties, snow and fog and other special weather conditions, drunken driving, recklessly changing lanes and other man-made causes, etc. All the above will be a threat to the security and safety of life and property of people. These factors make it very difficult to predict the surrounding traffic conditions. Therefore, it is very important to research the real-time and validity of emergency message broadcast in VANETs.Based on the existing robust broadcast protocol, we propose an improved BPAB (Binary-Partition-Assisted Broadcast) protocol, adding an innovative mini-DIFS (mini-distributed interframe space) mechanism, enabling emergency messages to access the channel quickly and efficiently, making it greatly reduce the access channel delay, improving the message dissemination speed of emergency message. We adopt an irregular binary-partition-based approach and give the farthest region within the source’s transmission range the highest priority, using different widths for different vehicle density. It can find the farthest effective area including the candidate relay node within the transmission range of the source more quickly and effectively. And achieve to further reduce the delay and improve the message dissemination speed.In this paper, the improved BPAB protocol has been used under the highway(directional broadcast) and the intersection mode broadcast conditions, and we have done the theoretical analysis and performance simulation. In the highway scenario, we compare the improved BPAB protocol with UMB (Urban Multihop Broadcast) protocol, SB (Smart Broadcast) protocol, BPAB protocol about the one hop delay, message progress and average message dissemination speed under both the single-source configuration and the multiple-source configuration conditions. In the intersection scenario, we compare the improved BPAB protocol with the AMB (Active Magnetic Bearing) protocol, BPAB protocol about the one hop delay, message progress, average message dissemination speed and packet delivery ratio as described above. In conclusion, the improved BPAB protocol has obvious advantages in both scenarios, and proves to be an effective emergency message broadcast protocol in VANETs.