Internet Protocol Television(IPTV)是一種利用寬頻網路做媒介傳輸電視影像的服務系統。在IPTV系統內由於網路頻寬的不足，因此用戶端無法一次接收到所有的電視頻道，所以只有在做頻道切換時才能接收到新的頻道串流，而導致頻道接收延遲的狀況產生。而現有的文獻上對於此問題其中一種解法是利用預收多個頻道的方式，預先接收未來可能會收看的電視頻道，當下次換台收視這些頻道時，就可以立刻觀看新頻道而減少換台延遲時間。
在P2P IPTV network下，利用P2P的特性藉由peer本身具有可用的上傳頻寬來協助分擔伺服器的負載，因此在P2P IPTV系統內，使用者所觀看的頻道部分來源是來自其他peer，也因如此peer在資源分享時會產生分享量不一的情形產生，由目前文獻的量測可以得知在P2P網路架構下會有自私的free-rider (無貢獻頻寬)使用者存在，這些使用者在P2P網路內的行為是只下載卻不上傳資源給其他使用者，造成系統資源使用效率低落，因此若free-rider採用預先收取額外的頻道內容且未分享給其他peer時，將會導致與其相連的peer執行頻道切換時無法獲取觀看的頻道串流，而被迫使得頻道切換時間增加。現有的P2P IPTV頻道快速切換方式並沒有對不同貢獻頻寬的用戶採取不同的服務措施，所以對free-rider沒有預防方法。因此本研究基於一個P2P IPTV快速換台的機制下，設計了一種避免free-rider佔據頻道的頻道切換機制，貢獻越多上傳頻寬的peer能獲得越多的預收頻道，導致較少的頻道切換延遲。此機制包含兩個步驟，第一步先量測peer的上傳貢獻程度，並給予排名，第二步則在peer下次做換台時利用該peer不同排名的程度，給予不同頻道收取數量，以此防止free-rider佔用多數的頻道資源不上傳導致接收peer無法順利接收串流內容而使得頻道換台延遲。

Internet Protocol Television (IPTV) is a broadband network streaming service through the Internet. Due to Bandwidth limitation, viewers cannot receive all TV channels in the STB. Therefore, viewers can only receive a new channel when they are switching to it. This leads to a longer channel switching delay. One of solutions to decrease the channel change delay is using the pre-join multi-channels which are potential channels viewers may switch to watch them.
In the p2p IPTV network, using the p2p property, peer can decrease the server overhead by contributing their upload bandwidth to other peers. Since part of the source is from other peers, rather than entirely by the server, this causes the imbalanced resource sharing between the peers. Free-rider is a peer that doesn’t contribute resources but consume service in p2p networks. Researcher have conducted measurements in real p2p application and observed the free-rider behavior could make inefficient utilization of the system resource. Hence, if we take the channel switching scheme by pre-join multi-channels to the free-rider, this will make the free-rider’s neighbors can’t receive the watching channel content when they switch to the channel, that increase the channel switching delay resulting from the free-rider. Existing fast channel change scheme doesn’t adopt the differential services according to the peer contribution in p2p IPTV, and thus it can’t prevent the free-rider, making the channel change blocked.
This thesis focuses on a p2p IPTV fast channel switching mechanism. We design a new channel switching scheme in which a peer contributing more upload bandwidth will receive more pre-join channels and consequently get better channel switching quality. This proposed method contains two steps. In the first step, we measure the peer uploading bandwidth and rank it. The second is that the system will give it the different channel receiving quantity according to its rank when a peer switches channel on the next time. This will prevent the free-rider occupying the multiple channels without uploading to other peers which suffer from the more channel switching delay.

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