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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/8873


    Title: 無線網路上多媒體傳輸服務之效能改善與研究;Performance Improvement and Research for Multimedia Transmission Services based on Wireless Networks
    Authors: 葉生正;Sheng-Cheng Yeh
    Contributors: 電機工程研究所
    Keywords: DECT;PRMA;允入機率;假釋放機制;ITU-T H.263;DECT;PRMA;Permission probability;Pseudo Release Scheme;ITU-T H.263
    Date: 2000-06-22
    Issue Date: 2009-09-22 11:36:50 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 在有限頻寬的無線網路中,若要提供語音、數據、影像、甚至視訊等多媒體資料的傳輸服務,勢必要有效率地提高傳輸的效能並充分利用系統容量,以符合各種不同資料型態之服務品質 (Quality of Service- QoS) 的需求。而本論文之研究以分時多工 (TDMA) 的通道存取技術為主軸,先探討無線網路之DECT系統(TDMA/TDD) 中媒介存取控制 (MAC) 方法的改良,並提出基地台與行動使用者之間的上下鏈路 (Up-Link and Down-Link) 機制及無間隙的細胞間交遞(Handoff) 方式等,使有效地利用系統容量並降低資料的傳遞延遲,因此提升整體效能的QoS。 另外,進一步地歸納與分析相關的文獻報告,發現分封交換的無線網路環境,以改良TDMA和Reservation-ALOHA之封包保留多工存取 (Packet Reservation Multiple Access- PRMA) 的方式,利用語音檢測器 (Voice Detector)的技術釋放靜音時的多餘頻寬等,較能有效地改善系統使用率,才有可能提供多媒體的資料傳輸服務,並與有線的區域網路相結合。 而再經由我們更深入的分析和參考相關論文的研究,以動態調整所謂行動使用者的允許機率 (Permission Probability),即基地台允許其佔有某時槽通道傳輸資料的機率,將更為有效地改善語音封包資料的遺失率、數據資料的平均傳遞延遲與系統的利用率等。所以,我們就從純語音使用者、語音和數據資料整合、一直到同時提供語音、數據和視訊使用者的多媒體環境,完整並連貫地研究相對應的運作機制,以期在有限頻寬的無線網路中探討提昇QoS的方法,且分析模擬其效能改善的情況。然而數學分析與電腦模擬結果也正如所預期,我們所提出的改善方法與運作機制確實可增進系統之整體效益。 A new scheme for the integration of video, voice and data transmission over the Packet Reservation Multiple Access (PRMA) is proposed in this thesis. We focus on low bit-rate video applications like video conferencing and visual telephony for wireless networks. The ITU-T H.263 standard provides a solution to the need for low bit-rate video compression under 64Kbps. In this thesis, the proposed protocol assumes that each voice terminal follows a traffic pattern of talk spurts and silent gaps with dynamic permission probability, and we assign the permission probability of voice terminals to be 6.4 times of data terminals. Also, each video terminal has the highest permission probability to access the available slot based on ITU-T H.263 standard. Again, we present a “Pseudo Release” scheme to release slots reserved by video terminals according to the contents of each video transmission buffer, and the active voice or data terminals can temporarily access the additional slots to improve the performance without sacrificing the video capacity of the system. The packet dropping probability of the active voice terminals, the mean delay of the active data terminals and bandwidth utilization of the system are superior to the original PRMA protocols', as indicated in simulation and analysis results.
    Appears in Collections:[電機工程研究所] 博碩士論文

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