無線寬頻網路（如WiMAX）針對需要較大傳輸頻寬的影音串流服務應用（如VoD、IPTV等等）提供了一個較佳的傳輸環境，但是過多的影音串流服務仍然會造成無線網路的擁塞，因此，如何疏解無線網路的流量並提供使用者較佳的影音串流服務品質便是值得研究的問題。我們在本論文中提出了封包代回與複製機制，針對提出相同連線要求的影音串流，透過封包的複製來減輕無線網路的流量，另外我們針對不同優先權等級的影音串流，提出了連線允入控制機制及低優先權封包丟棄機制，透過延遲低優先權等級影音串流的進入或是在網路擁塞的情形下，藉由丟棄低優先權影音串流的封包來降低其位元率（Bit Rate），如此我們便可以讓其它高優先權的影音串流得到較好的服務品質。
我們在Linux平台上設計並實作了一部用戶端閘道器，用來監控通過WiMAX網路上影音串流連線的封包，並提供封包代回與複製、頻寬要求封包的截取、影音串流位元率的量測及通知丟棄低優先權封包等功能，另外我們在影音串流伺服器的部份也撰寫了提供影音串流優先權等級及低優先權封包丟棄的程式，透過這些功\\\能來配合完成上述的三個機制，最後經由實驗結果來驗證我們的機制可以有效的疏解WiMAX網路的流量，並提供使用者不同優先權等級的影音串流服務品質。

Wireless broadband networks (such as WiMAX) provide more bandwidth for video streaming applications. However, too many streaming services over WiMAX would lead to congestion in the wireless links. How to relax the traffic on WiMAX links and provide users with a better QoS of streaming services is a worthy studying problem. In this thesis, we propose packet replication and duplication mechanisms for video streaming with the same connection requests to decrease traffic load over WiMAX links. Besides, we propose admission control and low-priority dropping mechanisms for video streaming with different priority levels. We reject low-priority video requests to guarantee QoS for high-priority video streams. If the network is congested, we decrease the bit rate through statistically dropping the low-priority video packets, which consequently improves the quality of high-priority video streams.
A subscriber gateway is implemented on Linux platform to demonstrate the above-mentioned three mechanisms. In the implementations, we classified the video priority levels and developed a scheme to drop low-priority packets in a multimedia streaming server. Finally, from the experimental results, we have shown that our mechanisms can decrease the traffic load over WiMAX links and provide users with different levels of service quality in multimedia streaming.

第一章 導論 1
1.1 研究動機 1
1.2 研究方向與實作 1
1.3 章節介紹 3
第二章 WiMAX上的影音串流 4
2.1 串流技術及其網路協定 4
2.1.1 RTP (Real-Time Transport Protocol) 4
2.1.2 SDP (Session Description Protocol) 5
2.1.3 RTSP (Real-Time Streaming Protocol) 6
2.2 WiMAX 7
2.2.1 標準簡介 7
2.2.2 服務類別 8
2.3 影音串流多工與具有優先權的流量控制 9
2.3.1 影音串流多工的相關研究 10
2.3.1.1 Voice Multiplexing 10
2.3.1.2 Video Multiplexing 10
2.3.2 具有優先權的流量控制 12
2.3.2.1 Admission Control 12
2.3.2.2 Priority-based Traffic Control 12
2.4 本論文的影音串流改進機制 13
第三章 WiMAX用戶端閘道器之設計 14
3.1 影音串流在WiMAX的傳輸 14
3.2 機制流程及演算法 17
3.2.1 封包代回與複製機制 18
3.2.2 連線允入控制機制 22
3.2.3 低優先權封包丟棄機制 23
第四章 Linux上的實作與結果分析 25
4.1 Linux平台上的實作 25
4.1.1 SGW上的實作 25
4.1.1.1 RTSP與RTP封包截取 25
4.1.1.2 頻寬要求封包的截取及Bit Rate的量測 27
4.1.1.3 NDLP封包設計 30
4.1.2 MSS上的實作 30
4.1.2.1 影音串流優先權等級程式的撰寫 31
4.1.2.2 低優先權封包丟棄程式的撰寫 32
4.2 實驗設備與環境設定 33
4.3 實驗結果與分析 35
4.3.1 實驗一 35
4.3.2 實驗二 36
4.3.3 實驗三 39
第五章 結論與未來工作 43
5.1 結論 43
5.2 未來工作 46
參考文獻（References） 47
索引（Index） 52

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