郭大維Kuo, Tei-Wei臺灣大學:資訊工程學研究所蔡坤益Tsai, Kun-YiKun-YiTsai2010-06-022018-07-052010-06-022018-07-052008U0001-3101200810012500http://ntur.lib.ntu.edu.tw//handle/246246/184880隨著VoIP(Voice over Internet Protocol)應用的蓬勃發展，近幾年，隨按即說(Push-to-Talk，PTT）的服務逐漸受到重視。此服務相似於傳統的無線對講機（Walkie Talkie），不同於原本全雙工的通訊模式，PTT 提供一個半雙工服務；且同一時間只允許內一個使用者發話，而群組中其餘成員只能聆聽。這篇論文中，針對PTT 服務，以目前最普遍使用的MOS (Mean Opinion Score) 作為聲音品質評估方法。我們重新分析聲音品質的因素，並經由實驗的方式進一步找出其與系統設計相對應的關係。在實務上，我們將針對封包延遲、延遲差異與封包遺失部份的分析，思考系統設計與提升聲音品質的相關對策。並從系統設計的角度與網路架構的規劃，提升整體服務的語音品質與系統的性能。With the popularity of VoIP, Push-To-Talk (PTT) services over the IP networks have gained their momentum. This research aims at essential design issues for speech quality of PTT services. We explore the relationship between speech quality and system design issues. MOS (Mean Opinion Score), that is raised by the ITU-T (International Telecommunication Union) as one of the most common benchmarks, is studied under factors in system designs and implementations. In particular, we will focus on the analysis of packet delay, jitter, and packet loss for PTT services. Experiments are designed and executed with the considerations of PTT characteristics. Our goal is to provide more understanding of MOS versus PTT and deliver insights in future PTT system designs.List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iist of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iihapter 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 1hapter 2 System Evaluation . . . . . . . . . . . . . . . . . . . . . . 5.1 Factor Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Evaluation Items . . . . . . . . . . . . . . . . . . . . . . . . . 8hapter 3 Evaluation Results and Discussions . . . . . . . . . . . . 11.1 Delay Assessment . . . . . . . . . . . . . . . . . . . . . . . . . 14.1.1 Transmission Delay . . . . . . . . . . . . . . . . . . . . 14.1.2 Buffering Delay . . . . . . . . . . . . . . . . . . . . . . 15.1.3 Remark . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.2 Jitter Assessment . . . . . . . . . . . . . . . . . . . . . . . . . 18.3 Packet Loss Assessment . . . . . . . . . . . . . . . . . . . . . 20hapter 4 Conclusions and FutureWork . . . . . . . . . . . . . . . 24eferences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26application/pdf478539 bytesapplication/pdfen-US隨按即說服務聲音品質網路電話封包延遲延遲差異封包遺失Push-to-TalkSpeech QualityMOSJitterVoIPthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/184880/1/ntu-97-P94922008-1.pdf