臺灣博碩士論文加值系統

摘 要

由於無線傳輸可使用的頻寬有限，因此如何在有限的頻寬資源下，使系統達到較高的流通量(Throughput)以支援最多的使用者是一個重要的研究的課題。本論文提出一個同時考量媒體存取控制(MAC)與通道實體(PHY)的跨層級(Cross-Layer)訊框傳送排程法則。針對即時性資料流，我們提出 具通道感知最早截止優先(Channel-Aware Earliest Deadline First, CAEDF)服務法則。CAEDF同時考慮用戶的通道狀況與即時性資料所能容忍最大傳送延遲時間(Maximum Latency)，使資料得以在用戶通道狀況良好情況下，透過較高速的調變技術傳送出去。針對非即時性資料流，我們提出具通道感知餘額輪流法則(Channel-Aware Deficit Round, Robin CADRR)服務法則來調整可傳送之封包數量，進而達到使用頻寬量的補償效果，如此，除可增加整體流通量，亦兼顧用戶使用頻寬量之長程公平性(Long-term Fairness)。
我們所提出的法則可在提升系統流通量的情況下，同時兼具滿足即時資料流的服務品質(Quality of Service)需求以及非即時資料流的長程公平性。模擬結果顯示在IEEE 802.16e網路中，使用CAEDF和CADRR法則傳送資料時，整體系統流通量比使用傳統EDF和DRR與Priority FCFS法則的整體系統流通量分別增加19%，使用者數量也分別增加了12.5%與53%。CAEDF法滿足了即時資料流之延遲要求，因此能夠大量減少封包的丟棄率，有效提升即時資料流用戶收訊的品質。而CADRR對於非即時資料流的用戶，無論用戶使用那種調變技術，透過額度的調整，可以達到長程公平性。

摘 要 I
誌 謝 II
目 錄 III
圖 目 錄V
表 目 錄VII
第一章 序論1
1.1 研究動機與目的 1
1.2 相關研究2
1.3 相關文獻6
1.4 論文架構7
第二章 IEEE 802.16e無線都會網路與無線通道8
2.1 系統架構8
2.2 媒體存取控制層 9
2.2.1 物件模型之對照關係9
2.2.2 頻寬要求機制 11
2.2.3 頻寬分配機制 13
2.2.4 資料流分類13
2.3 實體層15
2.4 都會型網路之無線通道20
第三章 跨層級的排程法則23
3.1 無跨層級排程之問題23
3.2 排程之設計原理 24
3.3 CAEDF和CADRR之架構26
3.3.1最大等待訊框數之計算器 28
3.3.2 通道狀況因素之計算器32
3.3.3 通道門檻值33
3.3.4 CAEDF法則34
3.3.5 CADRR法則37
3.4 訊框之排程流程圖41
第四章 效能評估44
4.1 模擬環境與參數 44
4.2 模擬結果與討論 49
4.2.1 方案1之模擬結果(固定式接取用戶，無雜訊之通道)49
4.2.2 方案2之模擬結果(移動式接取用戶，遮蔽效應)50
第五章 結論58
參考文獻 60

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