近年來，車載隨意網路(Vehicular Ad hoc Network, VANET)的通訊技術已被廣為討論，其相關研究更是眾多的學者關切且研究的熱門議題。其主要之應用範疇，包括提供行車安全的服務以及便利生活的訊息，讓所有的用路人可以即時取得與傳遞與交通相關的資訊，以便提高行車效率，增進用路安全與舒適性。 過去研究中，如何在車輛間有效率的傳輸緊急事件訊息 (如撞車、濕滑、坑洞、讓道給救護車及警車等訊息)，是一個急待解決的議題。若採用IEEE 802.11傳輸協定，來進行緊急事件封包發送，將使車輛隨機發出封包，除了容易發生封包Collision現象，並且multi-hop的傳送也會因此造成無窮盡的封包延遲現象，為了確保緊急事件封包能在短時間內有效率的通知鄰近車輛，採用預先規劃車輛傳輸機制，將可以有效控制封包延遲現象。 本論文主要針對車間緊急事件的傳遞，提出一個利用TDMA-based MAC Protocols 。其利用道路節區的預先規劃，使用叢集(Cluster)之概念，以Cluster Header統一傳送訊息來取代各車自行轉送訊息，透過訊息之監控、重送機制、多頻道傳輸等特殊設計，來解決封包衝撞與延遲等問題，以減少不必要的傳輸成本與頻寬浪費，提高訊息傳送的效率與可靠性。實驗模擬顯示，本論文所提之方法，在某些條件下，確實能有效提供車輛間更快速且更可靠的資料傳送。 In recent years, the connective technology of Vehicular Ad hoc Network has been widely discussed. In the primary applications of VANET can be categorized by two classes: driving safety and convenient living. All of people have capability to acquire and transmit real-time traffic information which can definitely raise driving efficiency and vehicle comfort. How to efficiently transmit between vehicles the emergent messages such as accident, wet-street, pit, emergency service and police petrol is an urgent issue. In case the protocol IEEE 802.11 is adopted, the packet in transmission can easily cause not only collisions but also long-term delay. Due to the assuredness of emergent packet in shot time communication, the prior scheduling vehicle transmission function can efficiently control the packet lag. This research primarily focuses on emergent transmission between vehicles. The TDMA-based MAC Protocols will be utilized in this research. The pre-scheduling in segmentation of street would be adopted by the cluster prospective. The Cluster Header is able to substitute the individual signal which is transmitted by each vehicle. By applying the proposed message surveillance, re-transmission and multi-channel access mechanisms, the conflictive packet and signal delay problems could be solved to reduce consumption in cost and bandwidth and improve the network throughput and reliability. In the experimental simulation, in some hypothesis, the functions we presented indeed facilitate the message transmission between vehicles can be prompt and reliable.
