近幾年來，隨著WiMAX無線寬頻網路的快速發展和行動通訊設備的普及，行動即時影音群播服務如視訊會議與網路電視等群播服務也愈來愈受到重視。有別於IEEE 802.16-2004，IEEE 802.16e以及IEEE 802.16j支援行動設備之移動性，並擁有高速率、遠距離傳輸之傳輸特性，在這樣優勢的網路環境下，如何提供高速及具QoS保證之影音群播服務，儼然已成為一重要的研究議題。針對各個使用者不同的群播需求與接收資料的環境，其中包括影片解析度、延遲限制及相異的傳輸速率，BS該如何在滿足QoS要求的條件下，進行最有效的傳輸排程以節省頻寬資源的耗費，將是一項重大的挑戰。本論文擬在WiMAX 802.16j的網路環境中，考量Relay Station的加入，並基於OFDMA模式下，針對使用者所提出的IPTV服務，進行群播排程，以滿足其影片解析度及延遲時間之要求，並達到節省頻寬資源及最大的網路吞吐量之目的。模擬實驗說明本論文的群播排程機制在滿足網路中所有的QoS服務要求下，可減少影音資料傳輸的整體時間，並有效使用無線頻寬資源。 WiMAX Mobile and Multi-hop Relay (MMR) networks characterized by the long-haul communications and high-speed transmissions have attracted much attention in recent years. The broadband WiMAX networks are able to support wireless video services, such as mobile IPTV. In IEEE 802.16j networks, relay stations not only complicate the design of grouping and scheduling approaches but also impact the design of sub-channel allocation approaches. As compared with unicasting, multicasting can save the bandwidth consumption and thus gains multicast advantages. However, all MSs in the multicast group should apply a common modulation and hence the delay constraints of some MSs might not be guaranteed. This paper develops the OFDMA-based multicast mechanisms to maximize multicast advantages and network throughputs while the QoS of MSs can be guaranteed. Simulation results reveal that the proposed multicast mechanism outperforms existing multicast works in terms of multicast advantages, user satisfactory and throughput.
