由於手機、車用數位電視、筆記型電腦以及PDA等電子產品越來越普及，加上數位電視的提倡，未來在行動式裝置上收看節目的品質逐日重要，視訊編碼以及群播技術將成為影響服務的主要原因。視訊群播技術的主要問題是群組中的使用者可能因為移動而造成通道狀況有所變化，WiMAX中提出了適應性調變與編碼方法(Adaptive Modulation and Coding scheme, AMC)，可以根據移動端(Mobile Station, MS)與基地台(Base Station, BS)之間的通道狀況調整傳輸時使用的調變技術。
可調性視訊編碼方法(Scalable Video Coding, SVC)是一種適用於使用者通道狀況不同的視訊編碼方法。SVC一般將影片編碼為一個基本層和數個改善層，使用者根據通道狀況收到個數不同的視訊編碼層。我們結合可調適調變技術與編碼方法以及可調適視訊編碼方法，用來改善系統中使用者收到的影片品質。
影片在多媒體伺服器用可調適視訊編碼方法將影片分層後，必須經由基地台根據通道狀況群播給行動台(Mobile Station, MS)，我們提出一個中央控制伺服器(Intermediate Control Server, ICS)，ICS處理多媒體伺服器和基地台之間的信令，它重新封裝接收到的視訊編碼分層，基地台可根據重新封裝後的封包訊息傳送不同分層數給不同通道狀況的使用者。利用模擬的方式驗證了我們提出的方法，在不同狀況下都可以有效的改善系統中使用者接收到的影片品質。

According to the popularization of consumer electronic products such as cell phone, vehicle digital television, notebook and PDA (Personal Digital Assistance), etc. and the promotion of digital television, the perceived video quality on mobile device becomes more important in the future. Video encoding and multicasting technology have huge influence on digital television service. The major issue in multicasting is that channel condition may vary with the mobility of users. AMC (Adaptive Modulation and Coding), which is a technology used when channel condition changes, is adapted in Mobile WiMAX.
SVC (Scalable Video Coding) is a video coding scheme used for different bandwidth level users. SVC encodes a video into one base layer and several enhancement layers. User receives different number of encoded layers based on their channel condition. AMC in WiMAX and SVC are combined to enhance the user perceived video quality in the system.
BS (Base Station) multicasts the SVC-encoded layers which is encoded in multimedia server to MS (Mobile Station) according to the channel condition. We propose an ICS (Intermediate Control Server) to deal with the signaling between the multimedia server and BS. The major task of ICS is to re-package the packets of the encoded layers received from multimedia server. BS multicasts different number of layers to users according to different channel condition. Besides, simulation results are used to prove that the proposed scheme is used to enhance the user perceived video quality effectively.

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