本論文考慮一種運作在感知無線電環境下的車載網路（cognitive vehicular network）應用問題：假設roadside unit（簡寫成RSU）會週期性地廣播一些資料給傳輸範圍內的車輛。受限於處在不同地理位置的車輛有不同的可供傳輸或接收頻道的條件下，RSU該如何選擇哪些收到全部或部分資料的車輛去使用哪些頻道以便「同時」轉播（relay）「一筆」原始或網路編碼後的資料給哪些鄰近未完全收到資料的車輛。我們稱此一問題為maximum interference-free multi-relay（簡稱為MIM）問題。此一問題的目標是要使得RSU和轉送資料的車輛能發揮最大的空間再利用率（spatial reusability），讓所有車輛所收到的資料封包總量的期望值達到最大。本論文的主要貢獻有三：一、我們首先將MIM問題建模為整數規劃（integer programing）問題，由此可知此一問題為NP-complete問題。二、針對MIM問題，我們首先提出集中式的媒介存取控制（medium access control，簡稱MAC）協定，稱為network-coding-assisted cooperative MAC（簡稱NC-MAC）。NC-MAC使用貪婪演算法來對付MIM問題。三、我們將集中式NC-MAC協定轉換成分散式NC-MAC協定。如果出於data offloading的考量，RSU不願意暫存已經傳送過的資料封包，那麼分散式協定便能派上用場。模擬實驗結果顯示：集中式NC-MAC協定和分散式NC-MAC協定在不同的網路環境下的效能表現各有優劣。網路規劃者可根據自身的需求來選擇合適的NC-MAC通訊協定。

This thesis considers an application scenario in a cognitive vehicular network: The roadside unit (RSU) periodically broadcasts a number of data packets. The vehicles in different locations may have different available licensed channels. We want to study the problem that how does the RSU determine which vehicles that correctly received some data packets from the RSU choose which channels to concurrently relay the original data or network-coded data to which vehicles that did not receive all data packets from the RSU such that the network throughput can be maximized. We call this problem the MIM (maximum interference-free multi-relay) problem. To the best of our knowledge, this problem has never been seriously studied before. The contributions of this thesis are mainly three-fold: First, we formally model the MIM problem as an integer programming problem, which is NP-complete in general. Second, we design a centralized MAC (medium access control), named NC-MAC (network-coding-assisted cooperative MAC), which employs a greedy algorithm to efficiently tackle the MIM problem. Third, on the basis of centralized NC-MAC, we design a distributed one which can work in a condition that the RSU does not want to buffer its transmitted data perhaps due to the consideration of data offloading. Simulation results show that in terms of throughput, centralized NC-MAC outperforms the distributed one, while in terms of algorithm execution time, distributed NC-MAC outperforms the centralized one. The network planner clearly can select the appropriate NC-MAC according to his needs.

目錄
論文審定書............................................................................................................i
誌謝......................................................................................................................ii
摘要.....................................................................................................................iii
Abstract...............................................................................................................iv
目錄......................................................................................................................v
圖次....................................................................................................................vii
表次 .....................................................................................................................x
第一章 緒論………………………………………….………………………………....1
1.1 研究問題…………………………………………………………………….......4
1.2 目標與貢獻………………………………………………………………….......8
第二章 相關研究...................................................................................................9
2.1 無線感知網路上的媒介存取控制協定.........................................................9
2.2 感知車載網路上的媒介存取控制協定.......................................................10
2.3 車載網路上的合作式通訊協定…………...…………………………….....…11
第三章 整數規劃模型………………………………………………………………...13
3.1 網路結構模型……………………………………………………………........13
3.2 通道模型………………………………………………………………...….....14
3.3 轉播端模型………………………………………………………………........16
3.4資料排程模型………………………………………………………….…........19
第四章 集中式NC-MAC協定…………………………………………………..….....20
4.1 RSU資料廣播期……………..……………………………………………......20
4.2 頻道偵測期……………...………………………………………………….....21
4.3 車輛beacon廣播期…………………….……………………………….........22
4.4 回報與請求期……………………………………………………………........23
4.5資料轉送期……………….………………………………………………........25
第五章 分散式NC-MAC協定……………………………………………………......33
5.1 RSU資料廣播期………………………………………………………….......33
5.2 車輛beacon廣播期……………………………………………………….......34
5.3 回報與請求期……………………………………………………………........35
5.4 轉播端選擇期與資料轉送期……………………………………………........36
5.5 每個時期的時間長度……………………………………………………........40
第六章 模擬實驗…………………………………………………………………......43
6.1 實驗環境與參數設定……………………………………………………........43
6.2 模擬器設計與實作.……………………………………………………….......48
6.3 模擬實驗結果……………………………………………………………........50
6.3.1 車輛傳輸半徑對效能的影響………………………………………..........51
6.3.2 最大編碼長度對效能的影響………………………………………..........53
6.3.3 Run-time throughput……………………………………………...…......57
6.3.4 Primary user數量對效能的影響…………………………………….......59
6.3.5 車輛數量對效能的影響…………………………………………...…......63
6.3.6 車輛速差對效能的影響…………………………………………….........67
第七章 結論…………………………………………………………………….........73
附錄………………………………………………………………………………......74
參考文獻……………………………………………………………………………..89

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