臺灣博碩士論文加值系統

近年來，從行動隨意網路衍生出的新興研究領域稱為車載隨意網路；早期被提出的車載隨意網路大多是採用地理路由的方式。而傳統的地理路由在僅考慮地理資訊的情況下，因沒有考慮道路的拓樸導致封包傳遞至無效路段(例如：死巷)而造成封包的傳遞失敗或經由修復策略等方式導致花費額外的傳遞成本，所以後續文獻提出以道路為基礎的路由協定，此路由協定通常假設車輛具有電子地圖並根據道路的路徑計算一條最短距離的路徑，則可避免封包傳遞至無效路段的議題，卻因沒有考慮路段實際的車流量情況，而造成傳遞至車流量較少的路段上而導致傳輸中斷。
為避免上述的問題，後續的研究則基於道路車輛資訊進而規劃完整路徑的路由方法被提出，此類方法可避免傳遞至無效的路段以及車流量較稀疏的路段，但是在規劃整條路徑需要完整的路徑資訊才能有效的評估，所以在路況資訊的收集與傳播將會造成封包負載的大幅增加，故本文提出藉由取得相鄰路段的路況資訊，並採用進一步探索的方式檢查相鄰的路段是否會造成傳遞失效，既可避免整體的路由路徑規劃，亦能達到節省廣播複雜路況資訊的開銷。同時，經由接收鄰近節點的地理資訊而決定選擇中繼節點的路由協定會隨著車輛的移動速度增加，導致採用了過期的地理資訊而造成封包傳遞至錯誤的方向或是傳輸失敗。因此，本文將分為三個部分：路況資訊的散佈與聚合策略－減少所需維護的路況資訊以及簡化路況資訊的內容、路徑選擇機制－檢查候選的鄰近道路與其相鄰的道路是否有足夠的車輛進行傳遞、封包轉遞選擇機制－預測節點位置以避免選擇傳輸範圍外的鄰近節點。
本文使用QualNet網路模擬軟體實作本篇所題出的方法與傳統的地理路由方法(GPSR, GPCR)並分析其效能。在模擬結果中，我們發現在車輛密度較高的場景中，本文所提出的方法與傳統的地理路由方法將不會有顯著的改善，其主要原因為在車輛密度較高的場景中，傳統的地理路由方法並不會因沒有考慮道路的車輛密度資訊而造成傳輸失敗或延遲，然而本文所提出的方法會隨著信標訊息間隔增加使效能逐漸優於傳統的地理路由方法；若是在各條道路車輛密度分佈不均勻的場景中，傳統的地理路由方法會因沒有考慮道路的車輛密度資訊而隨著通訊距離的增加而造成傳輸失敗的機率上升，故本文所提出的方法會隨著通訊距離的增加使效能逐漸優於傳統的地理路由方法。

The emerging research filed has been proposed is called Vehicular Ad Hoc Networks (VANETs).The scenario of VANETs is based on mobility fast and topology complexity. Thus, position-based routing is more suitable than reactively routing in VANETs. Because position-based routing just needs to maintain neighbor nodes’ information and doesn’t maintain the full route’s information, it also has better scalability than reactively routing when the topology changes too fast. But previously proposed position-based routing protocol for VANETs only consider position information, so the vehicle would route to the “void road segment”, then may course the packet’s route error or cost extra route overhead. For solving preciously problem, road-based routing protocol has been proposed.
In this paper, we present a position-based routing approach based on traffic exploration designed for inter-vehicle communication in urban scenario. The aim of the approach reduce beacon message overhead and increase the data packet ratio, but it doesn’t affect the overall throughput. Thus, the paper proposes the traffic information aggregation and dissemination strategy to exchange beacon message, route selection mechanism for traffic exploration and packet rely selection mechanism to prevent transmission fail problem.
We implemented the proposed method, GPSR and GPCR on QualNet. In the first scenario which vehicle density is high, simulation result shows our proposed method doesn’t have specific outperforms traditional position-based routing because packet delivery ratio doesn’t affect if traditional position-based routing doesn’t consider the traffic information. But in the second scenario which is uneven distribution of each road traffic, simulation result shows our proposed method has specific outperforms traditional position-based routing when the communication distance increment because traditional position-based routing doesn’t consider the traffic information.

摘要 ........... i
Abstract ........... iii
誌謝 ........... v
表目錄 ........... vii
圖目錄 ........... viii
第一章 簡介 ........... 1
1.1 研究背景 ........... 1
1.2 研究動機 ........... 1
1.3 研究方法 ........... 3
1.4 論文架構 ........... 3
第二章 文獻探討 ........... 4
2.1 VANET 與 MANET 的網路架構及特性 ........... 4
2.2 路由協定簡介 ........... 4
第三章 研究方法 ........... 21
3.1 行動模組與路由環境介紹 ........... 23
3.2 路況資訊的散佈與聚合策略 ........... 26
3.3 路徑選擇機制 ........... 32
3.4 封包轉遞選擇機制 ........... 34
第四章 模擬驗證 ........... 38
4.1 模擬環境 ........... 38
4.2 模擬評估方法 ........... 41
4.3 封包格式 ........... 42
4.4 結果比較與分析 ........... 43
第五章 結論與未來展望 ........... 49
參考文獻 ........... 50
Extended Abstract ........... 52
簡歷(CV) ........... 56

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