Research Of Priority-based Vehicular Emergency Warning Message Self-adjusting Dissemination Strategy

Inter-vehicle communication is one of the most interesting topics for vehicle ad-hoc network, emergency warning message distribution is deemed to be a key method to improve the road traffic security. The EWM dissemination require a higher reliability and validity. Therefore, how to design a timely, reliable emergency warning message distribution strategy has become a hot spot in the field of vehicle wireless communication in recent years. In this paper, an EWM dissemination algorithm, with a priority-based CCA self-adjusting method is proposed by the study of EWM. The main contents are as follows:First of all, the global research status about VANET message dissemination is introduced, and then the thought to solve the problem in each protocol is summarized, which is the foundation of the study.After that, the structure, features and protocol standards of vehicular ad-hoc network(VANET) are introduced in detail, and the retrospect of the protocols and applications about VANET is given. The necessity and demands,reliability and Timeliness,of EWM dissemination in VANET are analyzed.Thirdly, the flaw of common flooding routing manner,broadcast storm,is analyzed by summarizing the strategy of several recent algorithms that focus on the problem. By the type of emergency events, the improved limited transmission zone flooding rule is proposed to reduce the number of unnecessary relay nodes. Based on the hazard level and the importance, a message ranking method is designed,which would determine the forward order.Then,the number of redundant message is decreased by the design of data fusion mechanism,and then a CCA threshold self-adjusting method associated with the EWM priority is implemented. Base on the above all, an improving self-adjusting flooding routing strategy is proposed.At last, based on the Net Eye test-bed with Tiny OS, series scenes are designed to verify the efficiency of proposed methods.