在無線網路中，訊號容易受到訊號衰減、雜訊、干擾等外在因素影響，使得每個
使用者在不同的時間、不同的地點受到這些因素的影響所能夠使用的頻寬有所不
同。當使用者處在訊號衰減嚴重的地區時，封包遺失率增加，造成使用者收到的
影片品質不佳。可調式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。先前的研究提到的
方法主要是用低速率來傳輸視訊串流來確保每個使用者都能保有最低的視訊品
質，然而此方法對於可調式視訊資料而言，也就是同一張影像包含多種視訊品
質，反而限制了分配傳輸速率時的彈性。本篇論文針對可調式視訊資料的相依性
提出了傳輸速率排程的方法。透過為每個視訊資料決定其重要性，使得每個視訊
資料在確保相依性的情況下，能夠以其最適合的傳輸速率透過基地台廣播給接收
者，如此不但能更有效地利用無線網路頻寬資源，也讓使用者盡量避免收到無法
解碼的視訊資料。根據模擬的結果，我們的方法能在異質性使用者的無線網路環
境下有效增加成功傳送的視訊資料量，因此比現存的其他方法達到更好的整體視
訊品質。

Multicast video streaming allows multiple users to share the scarce wireless band-
width and watch video at the same time. In wireless networks, it is di cult to
control the perceived video quality since the channel quality of each client may be
di erent. Some multicast mechanisms transmit data based on the client with the
worst channel quality and provide all clients some video. However, the client with
the worst channel condition can result in very low average video quality. This pa-
per proposes a scheme, namely Scalable Video Multicast, to maximize the average
video quality of multicast clients under diverse channel conditions. The proposed
scheme uses the property that di erent modulation scheme can result in di erent bit
error rate and, thus, the transmission distance. Therefore, Scalable Video Coding
(SVC) in conjunction with transmission rate scheduling are exploited to improve
the average video quality perceived by the clients. The base layers of video frames
provide basic visual quality to the clients. Rate scheduling applying on the enhance
layers improves the average visual quality. Simulations show that the proposed rate
scheduling for SVC blocks can improve the average video quality of multicast clients
and outperforms other mechanisms in the literature.

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