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Author: 張哲瑜
Chang che-yu
Thesis Title: IEEE 802.11e HCCA 中改善傳輸效能之動態排程演算法
A Dynamic Scheduling Algorithm for Performance Improvement in IEEE 802.11e HCCA
Advisor: 黃政吉
Huang, Jeng-Ji
Degree: 碩士
Master
Department: 電機工程學系
Department of Electrical Engineering
Thesis Publication Year: 2008
Academic Year: 96
Language: 中文
Number of pages: 52
Keywords (in Chinese): 排程無線網路IEEE 802.11e
Keywords (in English): scheduling, WLAN, IEEE 802.11e
Thesis Type: Academic thesis/ dissertation
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  • 在IEEE802.11e的修正草案中,提出了根據平均的封包大小和資料產生率來計算TD (TXOP Duration)及SI (Service Interval)的演算法,但卻無法適用於VBR (variable bit rate)資料流。因此,在相關研究裡提出一個TXOP timer的機制,利用可變的輪詢週期以及可變的TD來適應VBR的資料型態。此外在TXOP timer 的基礎上,更有研究提出了利用佇列的資料量資訊QS (Queue Size)來分配準確的TXOP。雖然在TXOP配置方面可因此接近於完美,但在資料流量控管方面仍然有很大的改善空間。這是因為TXOP timer的增長速率為一平均值,因此在服務VBR封包時會導致若干封包無法在延遲範圍內接受服務。本論文將提出一個有效的排程演算法來改善TXOP timer機制,而作法主要是將QSTA (QoS Station)的服務分成輪詢及傳送兩部分。在輪詢部分將使用VBR最短的服務區間以準確的掌握VBR的封包產生時間;在傳送部分針對TXOP timer的傳輸限制提出無timer傳輸條件以及根據QS調整之變動timer傳輸條件來改善傳輸效能。經由模擬發現本論文作法可以有效的改善封包的延遲及遺失,並且能達到較高的吞吐量。

    In IEEE 802.11e, the provision of parameterized quality of service (QoS) is enabled by a polling-based scheduling. The scheduling deals with assignments of transmission opportunities (TXOPs) to QoS stations (QSTAs) at proper polling time instants, and it is inefficient for variable bit rate (VBR) traffic streams if both of the TXOP durations and the polling instants are estimated based on mean values declared in the respective traffic specifications (TSPECs). Although the efficiency can be improved by adapting TXOP durations according to the backlogged traffic reports issued by QSTAs, a problem still remains if polling instants are determined by mean-value timers. In this paper, we first point out the performance impairment that may be caused by mean-value timers, then a traffic scheduling algorithm using an adaptive timer is proposed to remedy this problem.

    中文摘要 i 英文摘要 ii 誌  謝 iii 目  錄 iv 圖 目 錄 vi 表 目 錄 vii 第一章  緒論 1 1.1 前言 1 1.2 研究目的 4 1.3 其他相關研究 6 1.4 論文架構 7 第二章  相關知識及作法介紹 7 2.1 HCCA機制介紹 7 2.2 HCCA運作 8 2.2.1 HCCA運作原理 8 2.2.2 ns-2簡介 9 2.2.3 HCCA的程式實作 10 2.2.4 NS2HCCA 12 2.3 HCCA參考排程演算法 13 2.3.1排程原理 13 2.3.2程式實作 15 2.4 SETT-EDD排程演算法 18 2.4.1 排程原理 18 2.4.2 程式實作 21 2.5 ARROW排程演算法 24 2.5.1排程原理 24 2.5.2程式實作 26 2.6 適應性排程演算法 29 2.6.1 排程原理 29 2.6.2 程式實作 30 第三章  論文作法介紹 33 3.1 ARROW與適應性排程比較 33 3.2 論文作法 36 3.3 程式實作 38 第四章  模擬結果 45 4.1模擬情境與參數設定 45 4.2模擬相關程式 45 4.2.1 Otcl程式 45 4.2.2 awk程式 47 4.3模擬結果 49 4.3.1 系統吞吐量(throughput)分析 49 4.3.2 封包平均延遲(mean delay)分析 50 4.3.3 封包遺失率(loss rate)分析 50 第五章  結論 52 參考文獻 53

    [1] [Online] Video Traces for Network Performance Evaluation.
    Available: http://trace.eas.asu.edu/
    [2] IEEE Std. 802.11e, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications– Medium Access Control (MAC) Quality of Service Enhancements,” Nov. 2005.
    [3] A. Grilo, M. Macedo, and M. Nunes, “A Scheduling Algorithm for QoS Support in IEEE802.11e Networks,” IEEE Wirel. Commun. Mag., vol. 10, no. 3, June 2003, pp. 36–43.
    [4] D. Skyrianoglou, N. Passas, and A. K. Salkintzis, “ARROW: An Efficient Traffic Scheduling Algorithm for IEEE 802.11e HCCA,” IEEE Trans. Wirel. Commun., vol. 5, no. 12, Dec. 2006, pp. 3558–3567.
    [5] I. Inan, F. Keceli, and E. Ayanoglu, “An Adaptive Multimedia QoS Scheduler for 802.11e Wireless LANs”, IEEE ICC, vol. 11, June 2006, pp. 5263–5270.
    [6] G. Boggia, P. Camarda, L.A. Grieco, and S. Mascolo, “Feedback-Based Control for Providing Real-Time Services with the 802.11e MAC,” IEEE/ACM Trans. Net., vol. 15, no. 2, Apr. 2007, pp. 323–333.
    [7] Chiapin Wang, Po-Chiang Lin, T. Lin,” A Cross-Layer Adaptation Scheme for Improving IEEE 802.11e QoS by Learning”, IEEE Trans. Neural Networks, Vol. 17, Issue 6, Nov. 2006, pp. 1661 – 1665.
    [8] B. Makarevitch, “Delay reduction for 802.11e hybrid coordinator,” Elect. Lett., vol. 40, May 2004, pp. 708–709.
    [9] [Online] IEEE 802.11e HCCA simulation using the Network Simulator 2
    Available: http://info.iet.unipi.it/~cng/ns2hcca/

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