點對點行動即時視訊廣播服務之設計與實現

Abstract

基於無線網路與行動運算技術的快速發展，我們可以在任何時間任何地點，將周遭有趣的事物拍攝下來，並透過無線網路即時與好友們分享。為了實現此一服務，傳統主從式架構，也就是所有收看端直接向發送端取得影音串流，將遭遇可擴充性問題。為解決此問題，一種可行的方式為使用點對點技術，使用應用層群體廣播來發送即時影音。然而，此服務中，由於各節點可能為具有高度可移動性且收訊不穩定的行動節點，這樣的情況下要建構穩定的應用層群體廣播樹，是個極具挑戰的研究課題。本論文中，我們設計且實現行動即時視訊廣播服務，使用點對點應用層群體廣播架構來提升服務之可擴充性，並提出最佳化機制來建構行動環境下穩定的應用層群體廣播樹。模擬結果顯示，本論文所提方案確實減少接收端平均收看延遲時間及服務中斷次數。

Advances in wireless networks and mobile computing technologies, it becomes possible to use a mobile device taping video at anytime and anywhere, and share the live video with friends in real-time through wireless networks. To realize this service, conventional client-server approaches which all receivers have to connect to the live video source, i.e. the mobile device, suffer from serious scalability problems. One possible solution to resolve the scalability issue is to apply peer-to-peer technologies and implement the system by using application layer multicast (ALM) scheme over receiver nodes. However, considering receivers that could be relay nodes and mobile nodes with high mobility, unstable wireless channels and bandwidth, to construct a stable ALM tree for relaying live video to all receivers becomes a very challenging research topic. In this thesis, the design and implementation of a live video sharing service in a mobile environment is presented. We apply P2P ALM schemes to improve the scalability of the services and propose ALM tree optimization schemes for constructing a stable ALM tree in mobile environment. Simulation results demonstrate that the proposed scheme reduce the average initial playback delays and service disruption during playbacks on receivers.