在透過網路播映熱門影片的服務上，週期性廣播協定是一項高效能的技術。它可以在伺服器傳送影片至大量客戶端時減少頻寬的需求。現存的週期性廣播協定中，Pyramid-based 協定因其簡單設計及公式化的操作方式而易於實做。其他如 Pagoda-based 或 Harmonic-based 協定則過於特殊或理論化而難以實際運用。
在本篇論文中，我們將針對週期性廣播協定中的頻道調整機制進行探討。頻道調整機制可協助伺服器在提供週期性廣播服務時，針對各影片的熱門程度，增減其使用的頻道，以便於對頻寬資源運用進行最佳化。熱門影片分配較多頻道，可縮短播放等待時間(startup latency)；反之，使用較少頻道的影片播放等待時間較長。這種頻道調整機制必須是「無縫」（seamless）的，亦即在頻道調整的過程中，使用者的收播不可被中斷或干擾。現存的週期性廣播協定頻道調整機制包括了 Seamless Fast Broadcasting (SFB)、Seamless Staircase Broadcasting (SSB)及 Flexible Periodic Broadcasting (FPB)。這些頻道調整機制都是針對特定週期性廣播協定而設計，前兩者甚至必須對原始廣播協定進行修改。這些機制不但較為複雜，不易套用於其他的廣播協定，且有可能降低原始廣播協定的效能。我們在觀察數種Pyramid-based 週期性廣播協定之後，發現這些協定在使用者緩衝記憶體(client buffer)的運用上具備共通的特性。基於此項特性，我們提出了一套通用性的無縫頻道調整機制，稱為 Stairway Channel Transition（SWCT）機制。在本篇論文中，我們提出的SWCT 機制並非針對單一的廣播協定而設計，它可以適用於任何具有規律性播放配置模式，且具備可避免頻道重疊條件的Pyramid-based週期性廣播協定。事實上，SWCT 可以應用於現今大部分的週期性廣播協定，而我們在文中分析驗證了其中四種較受歡迎的協定。相較於現有的SFB、SSB及FPB機制，SWCT更有彈性，並且不需要修改原本週期性廣播協定的架構，也不需要額外的緩衝記憶體，因此不會降低該協定的效能。

Periodic broadcasting is known as an efficient technique to deliver popular videos by reducing bandwidth requirement for transmitting streaming videos to simultaneous viewers. Most of the existing periodic broadcasting protocols can be recognized as Pyramid-based, which possesses regular behavior as function (mathematical formula) thus favored by high practicability. Others are designed by somewhat ad hoc or optimization procedures, such as Pagoda-based or Harmonic protocols.
In this dissertation, the channel transition problem, which is a noticed issue to be concerned about the variability of popularity of video in periodic broadcasting, is addressed. The channel transition schemes modify the channel allocation of a video by its hotness, thus optimize the bandwidth utilization. A hot video possesses more broadcast channels and shorter startup latency; otherwise, a video with fewer channels have longer startup latency. This kind of transition scheme should be “seamless,” i.e. the receptions of clients should not be interrupted or interfered. Present channel transition schemes such as Seamless Fast Broadcasting (SFB), Seamless Staircase Broadcasting (SSB) and Flexible Periodic Broadcasting (FPB) are dedicated to specific broadcasting protocols. The SFB and SSB even modify the original protocols. These schemes are rather complicated and difficult to apply to other protocols. Further more, they possibly decrease the performance of the original protocols. After the observation of several Pyramid-based broadcasting protocols, we found the common characteristic of the client buffer utilization. Based on the characteristic, we proposed a generic seamless channel transition scheme for pyramid-based broadcasting protocols, named as the Stairway Channel Transition (SWCT) scheme. The SWCT is applicable to any Pyramid-based protocol which conforms to our coordinated condition. Compared to the existing channel transition schemes, our design possesses more flexibility, while does not reduce the performance of the original protocols.

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