| Summary: | 碩士 === 國立交通大學 === 網路工程研究所 === 97 === Transportation System has become indispensable in our daily life. There are many commodities for driving assistance and entertainment, for example, Globe Position System (GPS), wireless digital TV, etc. Therefore, people expect to get more information or entertainment services from internet while driving. As the wireless devices become dainty and cheap, vehicular ad-hoc networks (VANETs) become a popular research topic. Intelligent Transportation System (ITS) is established to provide real-time, comprehensive and seamless traffic information, and to give a convenient, safe, and efficient driving experience. There are many applications for ITS, for example, emergency message, real-time traffic information and location based services or advertisements, etc. The dissemination of emergency message is one of the most important applications of them, and they are usually disseminated by broadcast. Therefore, it is an important topic to design an efficient multi-hop broadcast mechanism for vehicular ad-hoc networks, especially in urban areas. Broadcast in the urban area meets more problems than in the rural area because of the high density and high mobility of vehicles. In this work, we use multicast RTS to protect wireless channel and provide reliability. Moreover, we use the Global Position System (GPS) combined with the digital road map information to assist relay node selection. Meanwhile an adaptive beacon control is proposed to reduce control redundancy. At last, we evaluate our broadcast protocol in the real road map and real traffic flow. The simulation results show that the proposed broadcast protocol has superior performance in terms of packet delivery ratio, end-to-end delay and the number of collisions under different traffic load.
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