隨著無線通訊網路技術的進步，加上電子元件價格漸漸下降以及行車安全問題越來越受重視，VANET (Vehicle Ad-hoc NETwork)網路近年來成為各國矚目的研究議題。 VANET 網路之應用範疇，包括提供行車安全的服務以及便利生活的訊息。例如：當前方車輛發生事故時，能立即回報緊急訊息給後面車輛知道，避免連續事故的發生；或是開車族可以透過VANET 網路所提供之服務，獲取有關停車位位置之資訊。 由於VANET 網路應用很廣，有些訊息封包可能具有時效性，必須立刻送予後方車輛使其知道。目前關於道路上封包散播的方式，主要以同向車道上的車輛來幫忙散播為主。不過，使用此方式其效能是較低的，因為越後方之車輛必須等越久的時間才能收到此封包。若能利用對向車道與同向車道間所擁有之相對速度的優點，讓訊息封包早點到達較後方之車輛，相信對提升整體網路效能會有幫助。 故本論文提出一個利用對向車道之車輛來幫忙散播封包的方式，包括使用單一車輛及多台車輛來幫忙散播的情況。最終目標則是希望能有效地降低訊息封包散播給某範圍內所有車輛所花的時間。而經過模擬，本論文所提之方法，在某些條件下，確實能有比使用同向車道上的車輛來幫忙散播的方式有較佳的效能表現。 As the rapid progress in wireless communication technology and the cost of electronic component becomes cheaper, various kinds of applications have been deployed in real life. Among them, researchers pay more attention to Vehicle Ad-hoc NETwork (VANET) in recent years. The research areas of VANET can be divided into two major parts: safety application and comfort application. For example of safety application, if the car has crashed on the highway, the emergency information can be propagated as soon as possible to inform the cars behind the accident. And for the example of comfort application, if a gourmand can easily find some suitable restaurants by using the location based service through VANET. With the rapid applications on VANET, especially for the safety applications, it may be timeliness. Thus, the information must be sent to other vehicle quickly. Traditionally, the packet is sent through the vehicle on a road in the same moving direction to help data disseminating. This method may be low efficiency because the vehicle far from the accident area spends more time to receive the information. Moreover, the data disseminating time is too long. If we can take advantage of the relative velocity that exists between two different direction lanes to let the vehicle receiving the information quickly, the dissemination efficiency can be improved. In this thesis, we propose a method that using the opposite lane to help data disseminating. Two different situations are considered in the proposed method. The first one is to use only one vehicle in opposite lane to perform data disseminating. The other is to use multi vehicles for transmission in multi-hop manner. The goal of our method is to reduce the total cost of the dissemination time. In accordance with our simulation results, the proposed multi-hop method performs superior performance than the traditional method.
