近年來，隨著各項交通設施的完善及週休二日的推行，國人的用車時間也隨著增長許多，因此，如何提供道路及其他行車相關的資訊以協助駕駛以比較有效率的方式及路徑到達目的，和保護行車的安全是重要的議題。隨著無限通訊技術的進步及各種行動設備的普及化，如何應用無線通訊技術將行車事件（如撞車、坑洞、道路濕滑、讓道給警車或救護車等緊急訊息…）快速並有效的傳遞給駕駛，以維護行車的安全及急難的救助，是待解決的重要議題。此外，由於現今大眾對於上網需求遽增及行動通訊設備技術日益進步，如果提供車上乘客在行車過程有穩定且符合需求的網路服務，也是待解決的問題之一。
在智慧型先進車輛潮流的驅使之下，許多滿足車輛之間通訊的車載資通訊協定（如802.11P和DSRC）也陸續制定發布，由於路測系統（Road-side Unit）的建置價格昂貴且目前尚未普及，車載隨意通訊網路的通訊技術被廣泛的應用討論，其相關的研究更是眾多專家學者關切且研究的熱門議題，車間通訊是藉由專用短距離通訊技術(Dedicated Short Range Communication, DSRC) 來負責交通資訊系統的蒐集與傳遞的工作。DSRC主要是針對車與車、車與路側系統(Road Side Unit)以及智慧交通系統以達到提供安全駕駛、提高行車效率及乘客舒適乘車等目的，透過高速的傳輸速率並保證通訊的低延遲時間和低干擾，藉以確保系統的可靠性。
而在車載通訊網路中頻寬使用效能、資料存取的公平性以及封包衝撞等問題仍然是急待解決的，在Ad-hoc的傳輸方式裡，某筆訊息要傳送給後方車輛知道，通常是使用同一個頻道由同向車道之車輛依序來傳送。但如此一來，其效率是較低的。若是能夠同時利用兩個頻道來傳送訊息，區分車速穩定的車輛和車速不穩定或是新進入的車輛利用兩個不同的頻道，讓穩定的車輛可以利用原本的channel持續的傳送原本排定好的資料，並且讓不穩定的車輛利用另外一個channel來與原本穩定的車輛進行溝通或是傳遞訊息，這樣可以有效的節省訊息傳輸的時間。於是，本論文便基於此論點去寫作，提出一個在VANET 網路中能夠有效率地做完訊息散播之模型。

The time for citizen to use car has greatly gradually increased as the implementation of 2-days-off per week policy and the maturity of all kinds of transportation installation in recent years. Therefore, it is an important issue that how to provide road and traffic related information in order to help driver arrive destination efficiently and protect the safety of driving a vehicle. Besides, with the progress of wireless communication technology and the popularization of all kinds of mobile systems, how to apply wireless communication technology to pass emergency information, like car accident news, hole on the road, wet road and pass way to police patrol car or ambulance to drivers in a fast and efficiently way in order to provide driving safety and emergency help is an important issue that should be solved. In addition, due to the progress of wireless communication technology and the increasing of Internet needs, to provide stable and useful Internet service to passengers is also another issue to be solved.

第一章、緒論	1
第二章、國內外相關研究	7
2.1	Probability-based MAC Protocol	8
2.2	TDMA-based MAC Protocol	10
第三章、網路環境與待解決問題	15
3.1	網路環境與假設	15
3.2	Problem Formulation	17
第四章、	The Proposed MAC Algorithm	18
第五章、	實驗	23
參考文獻	27
附錄 英文論文	29

圖目錄
圖(一): Bitmap分配圖.	12
圖(二): Protocol State Machine.	14
圖(三):廣播競爭示意圖.	19
圖(四):廣播時槽決定示意圖 .	20
圖(五): 車輛接收到封包的延遲時間（Low Background Traffic）	24
圖(六): 車輛接收到封包的延遲時間（High Background Traffic）	25

表目錄
表I: Simulation Parameters	23

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