Research Of Vehicular Emergency Warning Message Dissemination Mechanism Based On CCA Threshold Adjustment

The problem of road safety and traffic congestion is increasingly more serious,and vehicle drivers always concern about the methods to avoid accident. Theemergency warning message (EWM) dissemination technology is employed to achievethe short warning progress among vehicles. How to disseminate EWMs to relatedvehicles quickly and efficiently becomes a popular topic in vehicular communicationfield. In this paper, a EWM dissemination algorithm, which is based on clear channelassessment (CCA) threshold adjustment and regional flooding with data fusion, isproposed. Moreover, NetEye test bed is used to verify the efficiency of proposedmethod. The main contents are as follows:First, EWM dissemination methods are introduced, and then the network structure,features and protocol vehicular ad-hoc network (VANET) are given in detail.Second, based on analyzing of flooding routing manner, an improving floodingrouting strategy is proposed. A regional flooding manner, which can reduce theunnecessary receivers, is used. Furthermore, data fusion mechanism is employed toreduce message redundancy.Third, the distributed coordination function (DCF) on MAC layer based onIEEE802.11is studied. After that, CCA threshold adjusting method, which aims toimprove EWM sending probability, is proposed. The interference model is given toillustrate the relationship between vehicle’s EWM transmissions. A multi-hop CCAthreshold-setting manner is proposed.At last, based on NetEye platform, series scenes are designed to verify theefficiency of proposed methods. The experimental results indicate that the proposedEWM dissemination mechanism has good reliability and validity.