無線傳輸下針對可調式視訊串流之確保服務品質的適應性技術

Abstract

在本文中，我們提出一套跨階層系統架構及演算法以提供服務品質的保證應用於可調式視訊串流。我們演算法不僅能降低單一使用者的視訊失真，也能夠應用到多個使用者情境，減少整體系統的視訊失真。服務品質是定義當系統傳輸給使用者影片時，使用者無法成功接收所有資料封包的機率小於給定的條件。當服務品質的要求越嚴格時，影片的播放就能越流暢，影像品質的變動程度也會越小。在最佳化問題中，同時考量無線通道的品質與位元率-失真(Rate-Distortion)的參數，透過適當的選擇封包長度與傳輸速度和通道編碼來達到服務品質的要求。模擬結果顯示我們的方法能夠提供穩定的影像播放品質或是很小的影像品質變動。

In this thesis, we present a cross –layer system architecture and a related algorithm for QoS provision in the scalable video streaming. The proposed algorithm not only deals with single user video transmission but also extends to multi-user scenario to reduce overall video distortions. The QoS is defined as the required target outage rate which is the probability that extracted video data is not successfully delivered to the receiver. The optimization framework is established to incorporate the effects of wireless channel conditions and video rate-distortion characteristic. It can minimize the video distortion under a target outage rate by adjusting payload length of a packet and modulation coding scheme. These parameters can be adapted dynamically based on the signal-to-noise ratio and rate-distortion parameters. The simulation results show the proposed scheme maintains a stable video quality or a small distortion variation.