應用PR-SCTP協定傳輸於MPEG-4/Audio AAC資料流之效能分析

Abstract

串流控制傳輸協定(SCTP)是一種新的通用傳輸層協定。它除了同時擁有TCP和UDP的優點外還提供一些新的功能，例如多串流傳輸(multi-streaming)和多位址傳輸(multi-homing)。 PR-SCTP是SCTP的延伸,它定義了不完全可靠度傳輸(partial reliable)的新服務。在本文中，我們提出一個多層次傳輸架構，利用PR-SCTP的不完全可靠度傳輸服務、SCTP的多串流傳輸以及伸縮性音訊編碼(scalable audio coding)的技巧來達成在不穩定的網路環境中仍然擁有可靠且高品質傳輸的目標。我們也使用k_XMIT和Timed這兩種可靠度參數設定法來評估這種多層次傳輸架構的效能。最後，我們利用NS-2網路模擬器來模擬我們所提出的架構。並經由模擬結果的統計跟分析得知使用Timed可靠度參數設定法可以確保穩固的即時傳輸效能，同時接收端也可以得到品質比較穩定的音訊。而且最重要的好處是使用Timed可靠度參數設定法不會造成傳輸時間的延遲，所以它可以被實際地應用在即時性的多媒體傳輸服務中。

Stream Control Transmission Protocol (SCTP) is a newly general-purpose transport layer protocol, which contains advantages of both TCP and UDP, providing some new features such as multi-streaming and multi-homing. PR-SCTP is an extension to enable the partial reliable service in SCTP. In this thesis, we propose a new multi-layer transport architecture which combines multi-streaming of SCTP, partial reliable service of PR-SCTP and scalable audio coding technique to still maintain reliable audio data transmission even under poor network conditions. Two different reliability definition schemes, k_XMIT and Timed, are also used to evaluate the performance of this proposed architecture. Finally, we implement it on the NS-2 network simulator and it is proved by simulation results that Timed reliability scheme can guarantee more robust real-time data transmission and get more reliable quality at the receiver side. The most important advantage of this approach is that it causes nearly no delay during a transmission session. So it can be a practical solution for real-time applications.