臺灣博碩士論文加值系統

合作式通訊是近年來廣被研究的通訊技術，使用者藉由彼此之間互相合作的傳輸方式，達到更好的傳輸效能。傳統式的視訊群播，為了使所有使用者都能接收到視訊資料，必須遷就於系統中通道狀況最差的使用者，整體系統的傳輸效率因而受到限制。合作式群播含有空間、時間、頻率的多樣性，可減低無線網路中通道衰弱、路徑損耗所造成的影響，因此適合運用於遞送視訊。

分層視訊編碼是一個新的技術，這個編碼技術能讓使用者依據其本身的通道狀況、服務需求等而解碼出相對應的視訊品質。此研究提出了兩個適用於遞送分層視訊的合作式群播方案，分別命名為機會合作式群播(Opportunistic Cooperative Multicast，簡稱OppCM)，以及編碼合作式群播(Coded Cooperative Multicast，簡稱CodedCM)。

機會合作式群播利用機會偵測，配合條件解調變，使第二階段成功解碼的使用者，能進一步解碼在第一階段偵測到卻未能解碼的資訊，因而提升整體系統的效能。編碼合作式群播則是一個可讓網路供應商主動調控的方案。在此方案中，基地台使用多解析度調變，遞送經由分層編碼過後的視訊資訊給使用者，收到視訊資訊的使用著，再藉由合作式群播的通訊技術，分送給更多使用者。

此研究探討了四種群播方案，分別為傳統式群播(作為比較的基準點)、單純合作式群播、機會合作式群播，以及編碼合作式群播。我們利用中斷機率，分析這四種方案的系統表現。根據模擬的結果，機會合作式群播的表現優於傳統式以及單純合作式群播。而編碼合作式群播由於其可主動調控的特性，更可符合網路供應商的需求，表現優異。從結果觀察，此研究提出的機會合作式群播，以及編碼合作式群播，皆為適用於遞送分層視訊的極佳方案。

Cooperative multicast is a promising technique to combat severe fading and path loss for wireless video delivery. In typical video multicast, nodes under the worst channel condition determine the video delivery quality, thereby limiting system performance. To tackle this problem, we propose two new cooperative multicast schemes called OppCM and CodedCM, respectively. OppCM performs opportunistic listening and conditional demodulating to enhance the system performance. The other scheme, CodedCM, delivers layer-encoded video with multi-resolution modulation through cooperative multicast. We analyze the system performance in terms of average outage probability for four multicast schemes, including direct multicast (for baseline comparison), pure cooperative multicast, and the proposed OppCM and CodedCM. We also compare their performance via simulations, which show that the proposed OppCM and CodedCM both outperform other two schemes, demonstrating that they are indeed excellent solutions to wireless scalable video multicasting.

謝辭 ii
摘要 iii
Abstract v
Contents vi
List of Figures viii
Chapter 1 Introduction 1
1.1 Wireless Video Multicast 1
1.2 Scalable Video 2
1.3 Cooperative Communications 2
1.4 Related Works and Motivation 3
1.5 Solution 4
1.6 Thesis Organization 5
Chapter 2 Multicast Schemes for Scalable Video 6
2.1 Direct Multicast (DM) 6
2.2 Pure Cooperative Multicast (PureCM) 7
2.3 Opportunistic Cooperative Multicast (OppCM) 7
2.4 Coded Cooperative Multicast (CodedCM) 11
Chapter 3 System Analysis 14
3.1 System Model 14
3.2 Received SNR Computation 15
3.3 Average Outage Probabilities Derivation 25
Chapter 4 Performance Evaluation 30
4.1 Environment and Parameter Settings 30
4.2 Simulation Results 31
Chapter 5 Conclusion 40
Reference 41

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