隨著WiMAX無線寬頻網路的快速發展，如何提供高速及具QoS保證之影音群播服務，如視訊會議、網路電視與數位電視廣播服務等，已成為一新興且重要的研究議題。針對一提供影音服務的BS而言，有效的群播排程較個別傳輸排程節省頻寬，然而，某些傳輸連線卻可能因配合群播傳輸的速率而採用速率較低的調變技術，使得傳輸速度較慢而違反傳輸延遲限制，因此，BS該如何滿足用戶之QoS要求，並開發群播的機會以達到提昇網路的效能，將是一重大挑戰。本論文在不違反各行動主機傳輸延遲限制的條件下，探討如何設計一有效之群播排程演算法，其中更針對群播分群、傳輸速率搭配及封包切割等排程問題進行深入研究，以期達到最大化網路吞吐量之目的。模擬實驗顯示，本論文所設計的群播排程機制可確實滿足網路中所有傳輸連線之QoS要求，並有效減少影音資料之傳輸時間以最大化網路吞吐量。 The mobile WiMAX networks characterized by the long-haul communications and high-speed transmissions have received much attention in recent years. The WiMAX network is able to support the wireless video services, such as mobile IPTV or multimedia services. For those mobile users who subscribe the same IPTV program, the multicasting can save the bandwidth consumption and thus gains the multicast advantages, as compared with unicasting. However, all MSs in a multicast group should apply the same modulation and the delay constraint of some MSs might not be guaranteed. This thesis proposes an IPTV multicast approach aiming at maximizing the bandwidth conservation and overall network throughput. The proposed approach partitions the mobile stations that demand for the same IPTV program into several multicast groups and schedules them for network access such that the multicast advantage can be fully explored while the delay constraints can be satisfied. Simulation results reveal that the proposed multicast mechanism outperforms existing work in terms of the multicast advantages, user satisfactory and network throughput.
