An Improved Coded Repetition Scheme for Safety Messaging in VANETs

Safety messaging plays an important role in Vehicle-to Vehicle (V2V) communications. By broadcasting packets via an 802.11 based technology, each vehicle informs the neighbors with its real-time status. Since this kind of information is life-critical, it should be received by all the adjacent vehicles with very high probability. In the previous work, we proposed a coded cooperative repetition approach for reliably broadcasting safety message in VANETs. It improves message's reception rate by repeating the received messages and share the scarce wireless bandwidth by coding two repetitions together. However, this method also introduces overheads. Almost 40% of all received coded repetitions are useless due to suboptimal coding decisions. In this paper, we improve this coded repetition method by providing it with more accurate information to guide the coding process. This enhancement incorporates three main techniques: reception rate estimation, neighbor state collection and opportunistic coding. Our experiments show a significant performance improvement. The overhead is reduced from over 40% to around 10% and the reception rate is increased by 15%.