隨著高畫質影音串流的興起，使用單一無線存取介面的行動主機(Mobile Station, MS)接收影音串流時可能會發生頻寬不足的問題，導致影片畫面可能產生大量馬賽克或停格的現象，為了解決上述問題，本論文在WiFi和LTE的多重無線存取技術(Multi Radio Access Technology, Multi-RAT)網路環境中提出SVC影音串流的分流機制(SVC Stream-Splitting Mechanism, SSSM)，在我們所提出的SSSM中，一條SVC影音串流會從影音串流伺服器經由WiFi和LTE傳送到MS，但是當WiFi的可用頻寬降低時會導致封包遺失率上升，所以MS會每隔一段時間量測在WiFi網路中的平均封包遺失率(Packet Loss Rate)與單位時間的吞吐量(Throughput)。為了讓伺服器可以在LTE和WiFi兩個介面間做適當的分流，我們修改Real-time Transport Streaming Protocol (RTSP)協定的DESCRIBE Message，當平均封包遺失率超過某個臨界值時，MS會使用單位時間的吞吐量來比對SVC每一層的Bit Rate以計算出要經由WiFi傳送的層級。另外，因為影音串流經由WiFi與LTE分流後會產生封包亂序的情形，我們在Real-time Transport Protocol (RTP)協定中新增一個欄位(Common Sequence Number)來重組影音串流的封包。最後，我們使用Linux平台來實作本論文所提出的SSSM，從量測結果中我們驗證有使用分流的單位時間吞吐量比沒有使用分流時來的高，而且影片的畫面品質也會比沒有使用分流時來的好。

With the emerging of high-definition video, a mobile station (MS) using a single radio interface may suffer insufficient bandwidth, leading to serious mosaic or even frame-frozen phenomenon. To solve the above problem, in this thesis, we propose an SVC Stream-Splitting Mechanism (SSSM) using multi-radio access technologies (Multi-RAT). In our proposed scheme, an SVC (Scalable Video Coding) streaming server divides a video stream into two sub-streams, and each sub-stream is delivered, respectively, via WiFi and LTE to an MS. When WiFi network encounters congestion, packet loss rate (PLR) will largely increase. A threshold of PLR is therefore set to divert the transmission of a certain upper SVC layers to LTE. One of the major contributions in this thesis is that we modify the DESCRIBE message of Real-time Transport Streaming Protocol (RTSP) such that the bit rate of each SVC layer can be delivered to an MS. Thus, an MS can compute the number of SVC layers to be diverted to LTE by comparing the received bit rates with the measured WiFi throughput. Additionally, since a video stream after the split into two sub-streams may produce out-of-order packets, we design a pre-buffer scheme to re-sequence the out-of-order packets by adding a common sequence number (CSN) in the Real-time Transport Protocol (RTP) header. Finally, we implement the SSSM on the Linux platform. From the experimental results, we demonstrate that the proposed SSSM with stream splitting can achieve higher throughput than that without using stream splitting. Also, the video stream received at MS can exhibit much better quality.

摘要 i
Abstract ii
目錄 iii
圖表目錄 vi
第一章　導論 1
1.1 研究動機 1
1.2 研究方法 2
1.3 章節介紹 3
第二章　SVC影音串流與多重無線存取技術 4
2.1 SVC影音串流技術 4
2.2 RTSP與RTP 6
2.2.1 RTSP 6
2.2.1.1 OPTIONS Request/Response Message 7
2.2.1.2 DESCRIBE Request/Response Message 9
2.2.1.3 SETUP Request/Response Message 11
2.2.1.4 PLAY Request/Response Message 12
2.2.2 RTP 13
2.3 Multi-RAT 13
2.3.1 LWA 14
2.3.2 SVC影音串流在Multi-RAT上的序列重組 15
2.3.3 MS的雙介面的層級架構 16
2.4相關研究 17
2.4.1 不考慮資料流型態的分配法 17
2.4.2 考慮資料流型態的分流法 18
2.4.2.1 一般影音串流的分流方法 18
2.4.1.2 SVC影音串流的分流方法 20
2.5本論文的機制 22
第三章 SVC影音串流的分流機制 24
3.1 SSSM的系統架構 24
3.2 RTSP連線建立模組的修改 28
3.3 決定SVC層級的分流與回復模組 29
3.3.1 計算封包遺失率與單位時間的吞吐量 29
3.3.2 決定在WiFi傳送的SVC層級 31
3.4 SVC影片動態層級配置模組 34
3.5 RTP協定的修改 35
3.6 使用PB重新排序的模組 36
3.7 SVC動態層級配置的舉例說明 38
第四章　Linux平台的實作與結果分析 40
4.1實驗環境與設備規格 40
4.2 在Linux平台上的實作 42
4.2.1 SVC影片動態層級配置模組 42
4.2.2 決定SVC層級的分流與回復模組 50
4.2.3 使用PB重新排序的模組 56
4.3實驗與結果分析 60
4.3.1 實作結果 60
4.3.2 實驗內容與參數的設定 63
4.3.2.1 固定 改變BG 64
4.3.2.2 改變 與BG 69
4.3.2.3 固定 與BG 71
第五章　結論與未來工作 73
5.1 結論 73
5.2 實作中所遭遇的困難與解決方法 74
5.3 未來工作 74
Reference 76
Acronyms 80
Index 83

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