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    請使用永久網址來引用或連結此文件: http://ir.lib.ncu.edu.tw/handle/987654321/8046


    題名: 即時細緻可調性視訊在無線區域網路下之傳輸效率最佳化研究;The study of optimal transmission for real-time FGS videos over WLAN
    作者: 黃逸隆;Yi-Lung Huang
    貢獻者: 通訊工程研究所
    關鍵詞: 效率;傳輸;頻寬;無線區域網路;最佳封包長度;Gilbert Model;bandwidth utilization;packetization;optimal transmission;WLAN;MPEG 4;FGS
    日期: 2004-07-06
    上傳時間: 2009-09-22 11:16:41 (UTC+8)
    出版者: 國立中央大學圖書館
    摘要: 隨著多媒體應用快速普及與多媒體資料編解碼技術成熟,加上無線網路蓬勃發展,多媒體資料在無線區域網路傳輸將是一個不可避免的趨勢。當封包在具有高錯誤機率的無線網路傳輸時,封包長度過小將使得封包檔頭的額外負荷提高,封包長度過大亦使封包發生錯誤機率提高,兩者皆會降低頻寬的使用效率。此外,在視訊編碼的過程中,不同型態的視訊封包具有不同重要性,若一視同仁地直接傳輸於無線網路中,將使得多媒體品質遭受嚴重的影響。 在本論文中,根據上述問題提出一套在無線區域網路下具有延遲限制的視訊封包最佳傳輸機制。本論文首先依據無線網路的傳送現況、封包檔頭的額外負荷、輪詢排程延遲、傳輸延遲、以及使用人數等因素,利用數學分析而得到最佳的封包長度。以此最佳封包長度為基礎,再針對MPEG-4 FGS特性以及視訊封包重要性差異,利用具優先等級的自動重送機制提出一套非對稱式視訊封包保護機制。本論文成果同時適用於所有無線區域網路,並且同時適用於IPv6以及IPv4網路層協定架構。模擬結果顯示,在IPv4/IPv6 IEEE 802.11 b/a/g等六種網路環境中,利用本論文所決定的封包長度傳輸於十種不同錯誤狀況時,均能達到最大頻寬使用率;此外,相較於其他固定封包長度進行傳輸,視訊品質亦有效地提升約1~2 dB。 Real-time streaming videos over IEEE 802.11 wireless networks are full of potential due to the great progress of digital compression and wireless network technologies. However, the delivery of video data with a large packet size may result in a high packet error rate on the error-prone channel of WLAN. On the other hand, using a small packet size may also increase the header overhead. This is a tradeoff between the packet error rate and header overhead. Additionally, considering the video encoding process, various video frames with different types have the distinct influence to the received video quality. An equal error protection to all video packets in the wireless network will degrade the video quality significantly. Therefore, this paper proposes an integrated optimal transmission strategy for delivering the real-time video data over WLANs. The proposed strategy first develops a mathematic closed form of the optimal packet size for achieving the maximum bandwidth utilization. The analyses are accomplished based on the current error situation, transmission overhead, scheduling delay, transmission delay, and the number of connections. Moreover, using the calculated optimal packet size, a prioritized ARQ mechanism is proposed for providing the unequal error protection to the FGS video frames with different significances. The analyses show that, the proposed strategy can be applied to both IPv4 and IPv6 networks and any type of 802.11 WLANs. Furthermore, with the combination of ten error patterns and three video sequences, simulation results reveal that the video transmission in IPv6/IPv4 IEEE 802.11b/a/g wireless networks can achieve the maximum bandwidth utilization while increasing the received PSNR up to 2dB by using the proposed strateg
    顯示於類別:[通訊工程研究所] 博碩士論文

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