因為車載隨意網路（vehicular ad hoc networks, VANETs）具有一些不同於傳統行動隨意網路（mobile ad hoc networks, MANETs）的特性，例如節點移動的速度較快、網路拓撲（network topology）的變化性較高等等，若直接將MANETs的路由協定使用於VANETs環境中，效果並不理想。因此針對VANETs特性所設計的路由協定相繼出現，其中有許多在近幾年內被提出來的VANETs路由協定都會利用道路上的車流量（vehicular traffic）來決定資料封包的傳送路徑。雖然選擇車輛密度比較高的路段進行資料傳輸可以減少傳送路徑中斷的狀況，但是我們發現這種做法卻會導致另外一個問題的發生：當某些車流量較大的主要道路經常被不同的資料流優先選為封包傳送的路徑時，在這些熱門路段上就可能會有很多的節點同時在發送封包，使得封包碰撞的機率大幅升高，而大量的封包碰撞將導致封包遺失，網路的效能勢必會受到影響。在本論文中，我們提出了一種以路口為基礎的路由機制（intersection-based routing scheme），稱為具資料壅塞意識的路由協定（data congestion-aware routing protocol, DCAR），除了考慮車流量的資訊之外，DCAR也會使用路段上資料壅塞的程度來協助路徑的選擇。由模擬結果可以得知DCAR的封包到達率相較於Greedy Traffic-Aware Routing Protocol (GyTAR)來說，有非常明顯的改善；另一方面，我們統計出資料封包的重新傳送次數來分析VANETs中資料壅塞的情況，結果顯示在目的節點每成功收到一個資料封包，其平均所重送的封包數量上，DCAR可以達到與VANET Load Balanced Routing Protocol (VLBR)差不多的功效，跟GyTAR相較之下都降低了許多，說明DCAR能夠利用即時的路段壅塞資訊，達到分散資料流量的目標，減輕封包碰撞的問題。

Because of different characteristics, the performance of traditional mobile ad hoc networks (MANETs) routing protocols is demonstrated poor in vehicular ad hoc networks (VANETs). Therefore, many routing protocols have been designed for VANETs during the past few years. Most of them choose the road segments with high vehicular traffic to construct routing paths. Although it can avoid path broken, a great amount of data traffic will construct on these road segments which incur serious packet loss due to packet collision. In this paper, we introduce an intersection-based routing protocol referred to as data congestion-aware routing protocol (DCAR). DCAR will consider both the vehicular traffic and the amount of data traffic on road segments to construct an optimal routing path. The performance evaluation of proposed protocol reveals significant improvement compared to Greedy Traffic-Aware Routing Protocol (GyTAR) and VANET Load Balanced Routing Protocol (VLBR) in terms of packet delivery ratio and number of retransmitted packets per received packet.

論文審定書 i
誌謝 ii
摘要 iii
Abstract iv
目錄 v
圖次 viii
表次 x
字母縮寫對照表 xi
第一章 導論 1
1.1 簡介 1
1.2 車載隨意網路的背景與介紹 4
1.2.1. 無線通訊的分類與架構 4
1.2.2. 車載隨意網路介紹 4
1.3 車載隨意網路路由協定 7
1.3.1 以拓撲為基礎的路由協定 7
1.3.2 以地理位置資訊為基礎的路由協定 8
1.3.3 以路口為基礎的路由協定 9
1.4 研究動機 9
1.5 論文架構 10
第二章 相關研究 11
2.1 以地理位置資訊為基礎的路由協定 11
2.2 以路口為基礎的路由協定 13
2.3 將車流量列入考量的路由協定 14
2.4 考慮到資料流量的路由協定 16
第三章 系統之架構與運作 18
3.1 設計動機與方向 18
3.2 功能及名詞釋義 20
3.3 運作方式 21
3.3.1 基本設定 21
3.3.2 估計路段上的車流量與資料壅塞程度 27
3.3.3 使用look-ahead機制決定出下ㄧ個路口 29
第四章 模擬結果與討論 39
4.1 模擬環境參數設定 39
4.2 數據分析與討論 41
4.2.1. 資料流數量 42
4.2.2. 資料封包發送頻率 44
4.2.3. 節點數量 46
第五章 結論 49
參考文獻 50

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