一個在點對點網路電視上提升播放品質之傳送機制研究

Abstract

現今點對點(peer-to-peer; P2P)服務，或同儕服務被廣泛地用來使用在網路電視及即時影音播放上。即時的P2P 服務可以提高網路的可擴充性及減少系統頻寬的消耗。目前市面上的網路電視應用很多，但其中幾乎沒有任何一項應用有針對使用者的行為來做分析。像是有些使用者在網路電視系統中會透過隨機的轉台來尋找他有興趣的節目。這樣的使用者行為模式會對系統造成很大的負擔。在這篇論文中，我們將會提出一套機制來降低使用者隨機轉台的次數。我們的目標是透過這項機制來降低使用者在網路電視系統上隨機的轉台，並且進一步地降低這種行為對系統所造成的負擔。 另外，假如同儕擾動(Peer Churn)的頻率非常地高以及同儕上載頻寬的不足，這些現象都將導致客戶端畫面播放不順，進而令使用者有不愉快的使用經驗(QoE)。因此，在這篇論文中，我們將會提出一套包含傳輸資料區分的資料排程及傳遞機制，用來將重要或者是迫切的資料優先進行傳送。播放時間即將到期之I-frame資料在我們的系統中將擁有最高的優先權。我們將會比較原始系統(不加方法)及我們提出的系統整體的效能，以及透過OMNeT++來設計一系列的實驗。最後，用實驗數據來驗證我們提出的方法是可行的。

Nowadays the peer-to-peer (P2P) systems have been deployed for the Internet television and live streaming. The real-time P2P service can have the advantage of scalability and heterogeneity in the existing network without modifying the underlay infrastructure. However, most of the common IPTV applications did not consider the user surfing behavior which causes great burden to the IPTV streaming system. In our proposed method, we design a mechanism to avoid users surfing channels. Our goal is to cut down the surfing frequency of the IPTV clients and alleviate the tracker loading during channel zapping of users. In addition, the high churn rate and insufficient upload capacity both are the inherent problems, which lead to the unstable playback smoothness, which results in a poor quality of experience (QoE). Therefore in the paper, we propose a content delivery strategy to distribute the important and instant data first for QoE enhancement. I-frame chunks near playback deadline are shared with the top priority. In order to achieve this purpose, a key-frame first mechanism is proposed to distribute the most important media content efficiently. We discuss the comparison of overlay performance and demonstrate that the proposed scheme is workable via a series of experiments on OMNeT++.