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標題: | 在無線網路中提供異質傳輸串流品質之分群式速率調節機制 Rate-Adaptive Video Multicast for Heterogeneous Clients over Wireless Networks |
作者: | Wei-Lun Liu 劉維倫 |
指導教授: | 周承復(Cheng-Fu Chou) |
關鍵字: | 即時傳輸,異質網路,傳輸速率調節, real-time streaming,heterogeneous environment,rate adaptation, |
出版年 : | 2009 |
學位: | 碩士 |
摘要: | 在無線網路環境下,多重傳送時考慮每個接收者的網路狀況並且定
期的做傳輸速率的調節是愈來愈困難的課題.首先碰到的問題是同時接 收多位接收者回報的訊息會在發送端發生碰撞,若使用分時多工的方法 當有大量接收者時會造成時間的浪費.之前的方法提出選一位網路狀況 最差的接收者當代表負責回報訊息,由此調整傳輸速率藉以保證網路上 的所有接收者都能接收到資料. 然而這些方法雖然保證每個接收者都能 接收到資料,卻處罰了處在網路狀況比較好能接收到高傳輸效率的一群 接收者. 因此在這篇論文中,我們提出一個分群式的異質性網路傳輸速 率調節機制讓每位接收者能夠依據他們所在的網路狀況接收自己能收 看最好的影片品質. 我們的方法會使用分群式的架構, 對每一群不同能 力的接收者選出一位代表者, 由這些代表者來預估整體接收者接收影片 品質的情形. 接者每張影片選擇最好的傳輸速率來達成最大化網路所有 接收者的收看品質. 最後由實驗能夠發現我們的方法會比之前找最差的 接收者當代表的方法平均收看的峰值信噪比(PSNR)好2 5dB,且也能 夠適應不同的網路狀況與不同的影片可變碼率(video bit rate). Rate adaptation for video multicast over wireless networks is a challenging problem because of network dynamics, variable video bit rates, and heterogeneous clients who may expect differentiated video qualities. Prior works on the leader-based scheme select the channel rate that can provide reliable transmission for the node who experiences the worst channel condition. However, this may penalize other nodes that can achieve a higher throughput by receiving at a higher rate. Hence, in this work, we investigate a rate-adaptive video multicast scheme that can provide heterogeneous clients differentiated visual qualities matching their channel conditions. We first propose a rate scheduling model that can select an optimal transmission bit-rate for each video frame in order to maximize the total visual quality for a multicast group subject to the minimum-visual-quality-guaranteed constraint. We then present a practical protocol, called CRAM, which constructs a cluster-based structure to characterize node heterogeneity and adapts the channel rate based on video quality perceived by the representative cluster heads. Since CRAM selects the rate by a sample-based technique, it is suitable for real-time video streaming without the need of any pre-process. The simulation results show that CRAM can produce a gain of 2-5dB in terms of the average video quality as compared with the leader-based approach, and adapt to network dynamics and variable video bit rates. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/44288 |
全文授權: | 有償授權 |
顯示於系所單位: | 資訊工程學系 |
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