在本論文中，我們考慮在車載網路的環境中，透過傳輸速率調控和網路編碼來處理緊急合作式資料交換的問題(urgent cooperative data exchange problem，簡稱UCDE problem)。對於UCDE問題，我們簡述如下：假設某個WiMAX（Worldwide Interoperability for Microwave Access）或LTE（Long Term Evolution）基地台傳送M個資料封包給一群車輛。由於車輛處在行駛狀態，且受到long-term path-loss、shadowing和short-term fading的影響，不見得每台車都能正確地收到這M個封包。假設車輛附近有路側設備（roadside unit，簡寫成RSU，例如WiFi access point）的存在。那麼我們希望能透過RSU的協助，使得RSU涵蓋範圍內的車輛能在三回合的資料傳輸之內盡可能地獲得M個資料封包。窮盡我們所知，目前尚未有任何文獻在探討UCDE問題。本論文的貢獻如下：我們證明UCDE問題為NP-complete問題。接著我們將UCDE問題轉換為一個效用總和最大化的整數線性規劃（integer linear programming）問題。整數線性規劃問題一般而言為NP-complete的問題。為了快速求出高品質的可行解，我們將提出一個新的媒介存取控制（media access control，簡稱MAC）協定，稱為UCDE-MAC。在UCDE-MAC中，RSU採用逆向歸納法（backward induction）和貪婪演算法（greedy algorithm）來求出上傳與下傳階段的資料傳輸排程，讓有缺乏資料封包的車輛都盡可能地獲得滿足。模擬實驗結果顯示UCDE-MAC確實能達成預期目標，且效能遠勝沒有網路編碼或速率調控的情況。

In this thesis, we consider to use network coding and rate adaptation to deal with the UCDE (urgent cooperative data exchange) problem. The UCDE problem is briefly described as follows: Assume that a WiMAX (Worldwide Interoperability for Microwave Access) or LTE (Long Term Evolution) base station broadcasts M data packets. Due to the mobility and the effect of long-term path-loss, shadowing, short-term fading, vehicles in the coverage of that base station may lose some data packets. Assume that there is an RSU (road-side unit), such as a WiFi access point, near to these vehicles. We hope that with the help of RSU, the vehicles that lost some data packets can receive all M packets as soon as possible. To the best of our knowledge, the UCDE problem has never been studied before. The contributions of our thesis are as follows: First, we model the UCDE problem as an integer programming problem with the goal of maximum sum of utilities. This implies that UCDE problem is NP-complete since an integer programming problem is generally NP-complete. To deal with the UCDE problem, we propose a new MAC (medium access control) protocol, called UCDE-MAC, which use backward induction and greedy approach to efficiently find out the suboptimal feasible solution. Finally, we conduct extensive simulations to validate the superiority of UCDE-MAC.

論文審定書…………………………………………………………………………i
誌謝 ……………………………………………………………………..…………ii
摘要 ……………………………………………………………………………….iii
Abstract…………………………………………………………………………...iv
目錄 ………………………………………………………………………………..v
圖次 ………………………………………………………………………………vii
表次 …………………………………………………………………………….…ix
第一章 緒論 ……………………………………………………………………1
1.1 研究對象……………..……………………………………………………2
1.2 拓樸結構所帶來的挑戰……………..……………………………………4
1.3 問題概述與論文貢獻………………………………..……………………7
第二章 相關文獻……………………………………………………..…………9
2.1 合作式廣播………………………………………………………………..9
2.2 具網路編碼的資料交換…………………………………………………..9
2.3 具網路編碼和速率考量的資料交換……………………………………10
第三章 模型與假設……………………………………………………………12
3.1 無線頻道模型與假設……………………………………………………12
3.2 車載網路拓樸模型與假設………………………………………………14
3.3 封包傳輸模型與假設……………………………………………………16
3.4 傳輸排程模型……………………………………………………………21
第四章 UCDE-MAC協定……………………………………………..………25
4.1 beacon廣播期……………………………………………………...……25
4.2 車輛回報期………………………………………………………………27
4.3 上傳與轉播期……………………………………………………………28
4.4 下傳與轉播期……………………………………………………………31
4.5 專有名詞介紹……………………………………………………………32
4.6 傳輸排程演算法…………………………………………………………38
4.7 排程演算法之時間複雜度分析…………………………………………45
第五章 模擬實驗結果與分析…………………………………………………46
5.1 實驗環境及參數設定……………………………………………………46
5.2 模擬器設計及實作………………………………………………………48
5.3 模擬實驗結果……………………………………………………………51
5.3.1 車輛的傳輸範圍對效能的影響……………………………………52
5.3.2 最大網路編碼長度對效能的影響…………………………………53
5.3.3 車輛數量對效能的影響……………………………………………55
5.3.4 資料數量對效能的影響……………………………………………57
5.3.5 車輛時速對效能的影響……………………………………………59
第六章 結論……………………………………………………………………61
附錄………………………………………………………………………………62
參考文獻…………………………………………………………………………69

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