由於現在有越來越多的人在車上收看數位廣播的串流影片，但是在車上收看因為移動的關係，所以常常會經過訊號接受不佳或者是受到建築物遮蔽而影響收訊的區域。因為訊號接受不佳而產生封包遺失的問題，當發生封包遺失那麼使用者的收看品質就會受到影響。我們希望讓使用者透過加入同儕網路而可以取回掉落的封包，因為只透過網路取回少部分的封包而不是整個串流影片，所以也可以降低網路的負擔。目前已經有很多方法在處理封包修補的問題，當中也很不少提出透過同儕網路來實現，我們參考並分析他們的策略並提出一套有效的封包儲存機制。
在本篇論文中，我們提出了一套階層式儲存機制，使用者可以透過同儕網路取回掉的封包，但也必須負責存取部分串流影片。我們的機制是控制影片封包的儲存份數，而儲存的份數是參考現在使用者數的多少來決定。這樣可以降低某些封包複製的份數過多，而某些複製份數太少的問題。如此一來就可以減少不必要的儲存以及降低使用者的負擔。

Due to more and more viewers using DVB-T to watch live streaming in vehicle, watching live streaming in vehicle will cross weak signal strength areas or signal blocked by high building. Packet loss problem occurs when the signal strength is weak and affects the video quality. Viewers will join the p2p networks for packet loss repair. Because the source of video streaming is from DVB-T and just request for lost packet from p2p network, our solution can reduce the usage of network bandwidth. In recently years, there are many strategies researching into packet loss repair problem. Using p2p network as the repair system is a hot issue. We reference and analyze their strategies, and then propose an efficient caching mechanism.
In this thesis, we propose a Hierarchical Caching Mechanism that viewers should join the p2p network and cache partial of video streaming. They can repair the lost packet from the p2p network. In our mechanism, we can dynamic control chunk replications according to the number of peers in the p2p network. It is used to avoid number of some video chunks’ replication is high and some low.

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