異質無線多網下視訊串流封包分送系統之跨層設計與研究

A Cross-Layer Packet Striping Framework for Video Streaming in Heterogeneous Wireless Networks

廖碩唯(Shuo-Wei Liao)

指導教授 ： 謝宏昀

國立臺灣大學/電機資訊學院/電信工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.00024

摘要

隨著科技的發展，掌上型行動裝置的運算能力已大幅度的提升，並能透過各種異質的無線介面，使用網路提供的各種服務與應用，尤其是使用視訊串流技術收看隨選視訊已成為相當重要的應用。然而，一般在行動裝置上的視訊串流皆是使用單一無線網路作為傳輸媒介，由於無線網路具有許多不良的特性，視訊串流在無線網路上的效果不甚理想。儘管部份相關研究提出同時使用多重路徑來提昇視訊串流的品質，但是並未考量到行動裝置上無線多網的異質性，對於進ㄧ步關於有限電力資源以及通訊費用方面的討論，更是付之闕如。
本篇論文提出一個能夠在異質無線多網下運作的視訊串流封包分送系統。透過即時考量異質網路的頻寬、延遲變動等特性，再佐以獨特的跨層式設計，希望能在考慮底層能量消耗以及通訊費用的情形下，提供給使用者更佳的使用經驗以及更長的裝置可用時間。本論文首先分析無線網路造成視訊串流效果不理想的原因，包括相對於有線網路較高錯誤率、頻寬及封包延遲時間的變異性。其次介紹本論文提出的封包分送系統，並特別描述如何使用跨層的資訊如訊框的重要性、電力資源的消耗量等，以決定封包分送的策略，達到最佳的收視品質。最後經由NS-2模擬的結果驗證，使用此篇論文所提出的幾個機制，可以有效的降低重要訊框的遺失率，並且能在有限的電力資源以及通訊費用之下，提供視訊串流影像畫質大約2~3dB的增益。

關鍵字

異質 ； 無線 ； 多網 ； 視訊串流 ； 封包分送 ； 跨層 ； 雙模 ； 多模

並列摘要

The objective of this thesis is to design and implement a cross-layer packet striping framework for video streaming in heterogeneous wireless networks.
Due to the great progress of processing speed of integrated chips and cost down of small size color screens in recent years, mobile devices today are able to display color video clips well and to connect to various wireless networks through different network interfaces. With those abilities the users always want to stream video on them. Traditional video streaming framework can always uses only one network interface. However due to the unstable characteristics of wireless transmission channels, the quality is not well after all.
In order to overcome this problem, this thesis tries to use the available links on mobile devices spontaneously to improve overall wireless networks reliability. A packet striping framework is designed to schedule the video packets to the links to provide better video streaming quality.
However, some resources such as communication fee or battery power on mobile device are valuable to users. To increase the feasibility of the packet striping framework, the usage of resource is also considered while designing the framework. Finally, simulations are conducted on NS-2 to show the effectiveness of the proposed cross-layer packet striping framework.

並列關鍵字

video streaming ； packet striping ； communication fee ； cross-layer ； packet scheduling ； heterogeneous ； wireless network

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