由於目前消費性電子產業崛起，加上許多服務例如數位影像廣播(DVB)及數位電視頻道的播送，隨時隨地經由消費性電子產品接收影音娛樂資訊已經勢在必行，且在無線接取網路技術的趨近成熟下，尋求殺手級的應用(killer application)以提供服務供應商以及消費者雙方面的利益共享，將會影響下一網路世代的發展趨勢，因此，視訊群播(video multicast)的應用被視為將會對一般大眾最有吸引力且最具有無限發展潛力的應用。 本研究主要發展於WiMAX無線接取網路環境，採用具有高彈性分配頻譜資源特性的OFDMA PHY層，利用二維的頻譜分配，加上SVC(Scalable Video Coding)影像編碼技術的分層方式，確實跨層地利用PHY層的使用者通道資訊，先針對頻率軸找出各自適合的subchannel，再針對時間軸作SVC影像分層群播，以達成本論文跨PHY層與MAC層的群播機制。 本文提出的跨層群播資源分配方法達成在有限的無線網路頻寬資源情況下，根據各個使用者與傳送端之間的通道狀況好壞，盡可能降低消耗的無線網路資源，並保證每個接收端的基本影像品質(fairness)，且有效(efficient)提升整體系統網路效能。 As a result of the rapid growth of the consumer electronics products and many services like DVB and digital channels begin broadcasting their content, receiving multimedia content through these devices anytime and anywhere becomes imperative. Furthermore, the technology of wireless access network is getting mature, therefore seeking a killer application to benefit service providers and consumers will make an impact on the next network generation. For this reason, video multicast seems to be a killer application that is attractive and has potential for development. This study is developed on WiMAX, the PHY technique adopted is OFDMA due to the flexibility of its resource allocation. By two-dimension resource allocation and SVC(Scalable Video Coding) technique for layered coding, we refer to every receiver's channel condition to find each appropriate subchannel from frequency domain, and then layered video multicast from time domain to attain the proposed cross-layer multicast scheduling. The proposed scheme achieves the objective that it takes cross-layer information into account, to minimize the resource usage according to every receiver's channel condition, to guarantee fairness of video quality of every receivers and to increase the throughput efficiently.
