https://scholars.lib.ntu.edu.tw/handle/123456789/150255
標題: | 視訊編碼技術於無線網狀網路之最佳化模型與效能比較 Modeling and Comparison of Video Coding Techniques for Video Streaming in Wireless Mesh Networks: A Network Optimization Perspective |
作者: | 蔡宗霖 Tsai, Tsung-Lin |
關鍵字: | 視訊編碼技術;無線網狀網路;最佳化模型;Video Coding Techniques;Mesh Networks;Optimization | 公開日期: | 2008 | 摘要: | 本論文主旨在研究並分析視訊編碼技術於無線網狀網路之最佳化問題。目前許多相關研究主要在追求無線網狀網路上最大的流量來最佳化視訊品質,然而對於視訊串流的品質來說,追求最大的流量並非一定是最好的。在最佳化視訊串流的品質時,也需要考慮不同的視訊編碼技術特性。在本論文中,我們首先分析了不同網路模型變因對於最佳化視訊品質的影響。我們藉由考慮了MPEG-4、FGS以及MDC三種不同視訊編碼技術的位元率-失真函數,建構一個視訊串流品質在無線網狀網路之最佳化數學模型並進行效能比較。從結果中我們發現雖然MDC有較差的編碼效率,但是當網路鏈結的容量變小時,MDC會有比MPEG-4與FGS更好的視訊品質。其次,我們考慮了最短路徑延遲、最少路徑跳躍次數以及最短路徑距離三種不同的路由層機制,來討論他們在使用不同編碼技術時,與視訊品質最佳化路由在選擇路徑與對視訊品質影響的差異。由此延伸模型的結果,我們發現最短路徑延遲路由是三種路由層機制當中表現最好的,特別是當選用MDC作為編碼技術的情況下,效能與視訊品質最佳化路由相差不到0.2 dB。最後,我們進一步考慮了傳輸功率控制與傳輸速率調整兩種媒體控制層機制,在使用不同編碼技術時對最佳化視訊品質的影響。我們發現在考慮了媒體控制層的機制後,FGS視訊品質提升之程度是三者中最好的,而MDC由於其解碼的獨立性,在不同網路環境下有較穩定的視訊品質。模擬結果顯示,在尋求視訊品質最佳化的目標下,在選擇不同視訊編碼技術時,需要考慮路由層以及媒體控制層機制所造成的影響。 The objective of this thesis is to analyze and optimize video performance using different coding techniques over wireless mesh networks. Most work focuses on achieving the highest throughput for performance optimization in mesh networks. However, this goal is not always the best for video streaming, and the characteristics of video coding techniques need to be considered. In this thesis, we first investigate the impact of network factors on optimal video quality. We build an optimization framework for video streaming in mesh networks by considering rate-distortion optimization of different coding techniques. The optimization problem can be formulated as a mixed integer nonlinear programming, and we evaluate the performance of different coding techniques, including MPEG-4, Fine Granularity Scalability (FGS), and Multiple Description Coding (MDC) in the proposed framework. We find that although MDC has poor coding efficiency, it performs better than MPEG-4 and FGS when the link capacity is small. We next extend the proposed framework to incorporate the impact of routing layer mechanisms, including minimum delay routing, minimum hop routing, and minimum distance routing. We discuss their difference from the optimal routing, and find that minimum delay routing performs best, especially when MDC is used. Finally, we extend the framework to incorporate the impact of MAC layer mechanisms, including transmission power control and rate adaptation. We find that among the different coding techniques, FGS improves most when using MAC layer mechanisms. MDC has stable performance for different network conditions due to the independency of multiple descriptions. We conclude that the optimal choice of video coding techniques should consider the routing and MAC layer mechanisms in mesh networks. |
URI: | http://ntur.lib.ntu.edu.tw//handle/246246/187993 |
顯示於: | 電機工程學系 |
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ntu-97-R95942101-1.pdf | 23.32 kB | Adobe PDF | 檢視/開啟 |
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