點對點科技已經被發展在多媒體內容傳遞方面並可減少伺服器建置成本，藉由點對點網路傳輸，隨選視訊服務有越來越熱門的趨勢。在點對點隨選視訊系統上的節點可以取得要求的視訊內容，以及分享相關資源給其它的節點，並且他們總是期望視訊的發送請求和開始播放之間的延遲時間能夠盡可能地短暫。然而由於節點有動態加入與離開的行為，以及節點有隨機存取操作的特性，這使得要求視訊內容的接收者不容易去找到合適的串流提供者。此外隨著高解析度視訊內容的逐漸普及，對視訊的網路頻寬需求可能會超過節點平均的上傳能力，而節點的快取也可能只會緩衝儲存部份的視訊內容。因此，如何在有限的頻寬資源下去提供有效的內容分佈機制與減少搜尋所造成的延遲時間是相當重要的。這篇論文設計一個結合網路編碼技術的交錯式雙層快取機制去提供快速地視訊內容搜尋和有效地視訊隨機存取。一個影片的片段是由多個大區塊組成，每個大區塊被切割成多個小區塊，再透過網路編碼技術，將這些編碼後的小區塊有組織地散佈並儲存到每個節點的兩階段快取，包含了前置快取和後置快取。前置快取目的是為了達到快速地找到父節點、降低起始延遲時間、快速地反應隨機存取操作；後置快取目的則是為了節點有限的儲存空間去有彈性地調整快取大小。另外論文也提出了加強與補償機制，這幫助去減少視訊播放延遲時間、更有效地運用節點有限的上傳能力。以馬克夫鏈為基礎的數學分析模組也被推導去計算大區塊遺失的機率，進一步地選擇合適的系統參數去改善系統整體效能。模擬的實驗結果顯示我們所提出的方法在不同的節點到達時間與不同的視訊位元率下的網路情境中，不論在起始延遲時間、隨機存取延遲、伺服器負擔的表現上都比其它文獻所提出的方法來的出色。

Peer-to-peer technologies have been developed for distributing multimedia content at low infrastructure costs. With peer-to-peer assisted operations, video-on-demand services have increasingly proliferated. Peers in peer-to-peer video-on-demand systems obtain requested video content and share resources to other peers of the system. Further, they expect the interval between the video request and playback start time to be as short as possible. However, due to the dynamic nature of peers and random seeking, it is difficult to find suitable streaming suppliers for those demanding content. Moreover, as high-definition video content becomes increasingly popular, bandwidth demand for high-definition video content may exceed average peer uploading capacity, and peers may only cache parts of video content. Hence, a scheme for providing efficient content distribution and reducing search delays under restricted bandwidth resources is critical. In this dissertation, an interleaving two-level cache with network coding scheme is proposed to provide rapid content searching and efficiently support random seeking. A video segment is composed of chunks, and each chunk is divided into blocks. These blocks are encoded by a network coding technique and distributed to different peers for storage in a local two-level cache, which includes a prefix cache and suffix cache. The prefix cache helps achieve rapid parent peer searching, low startup delays, and quick responses for jump operations. The suffix cache primarily provides a scalable cache size adjustment based on the limited storage space of peers. Additionally, enhancement and compensation mechanisms are provided to reduce playback delay and more efficiently utilize limited uploading bandwidth. We also present an analytical model based on the proposed Markov chain for determining appropriate system parameters to reduce chunk loss probability. Experimental results show that the proposed scheme outperforms competing schemes in terms of startup delay, jump delay, and server stress under different peer arrival times and video bitrates.

論文審定書 i
誌謝 iii
中文摘要 iv
Abstract v
Table of Contents vii
List of Figures ix
List of Tables xii
Chapter 1. Introduction 1
1.1. Background and Motivation 1
1.2. Contributions 6
1.3. The Organization of the Dissertation 7
Chapter 2. Literature Review 8
2.1. P2P Transmission Architectures 8
2.2. Network Coding 9
2.3. Data Distribution 11
2.4. Realistic Measurements of P2P VoD System 12
Chapter 3. The Proposed Scheme 14
3.1. Multisource Structure and Network Coding 14
3.2. Cache Design 17
3.2.1. Prefix Cache 18
3.2.2. Suffix Cache 21
3.3. Enhancement and Compensation Mechanisms 24
3.4. Discussion 27
Chapter 4. System Analysis 30
4.1. Analytical Models 31
4.2. Analysis Results 35
Chapter 5. Experimental Results 49
5.1. Experimental Environment 49
5.2. Startup Delay 51
5.3. Jump Delay 56
5.4. Search Failure Probability 60
Chapter 6. Conclusions and Future Work 64
6.1. Conclusions 64
6.2. Future Work 65
References 66

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