當在車輛中的乘客欲觀看視訊串流時，透過蜂巢式無線網絡請求視訊串流，即3G或3.5G網絡時，3G/3.5G網路可能沒有足夠的頻寬來獲得高品質的視訊串流。為瞭解決這個問題，請求者可透過短距離無線技術，例如:車載環境專用短程通訊 (DSRC)，詢問鄰近的車輛，幫助下載視訊串流再透過車載環境專用短程通訊 (DSRC)回傳給請求者。我們稱此情境為車用網路中之協同式視訊串流(Cooperative Video Streaming over Vehicular Network)。由於在行駛的汽車的環境下，車用網路的拓撲結構變化很快，協同式視訊串流有三個關鍵議題如下：（1）如何在快速變化的車用網路上動態形成協同組 (Cooperative Group)，以作為視訊串流之候選協助者提供較佳的視訊品質，（2）如何排程鄰近的車輛幫助視訊串流之下載與轉送和（3）如何預測可能變動的網路環境，並做重組調整，選擇適合的協助者以提供視訊串流之下載。基於這些議題，本論文提出(1)可連線時間之預測(Prediction Life Time)來找出適合的鄰近車輛來達成協同式視訊串流，(2)根據鄰近車輛的可連線時間之預測或者是可分享之3G/3.5G網路頻寬來排程視訊串流，當從鄰近的車輛收到額外視訊串流就可以更增進視訊的品質，而達成協同式視訊串流。此外，(3) 緩衝區感知估測 (Buffer Aware Estimation) 將根據緩衝區和串流的情況決定是否重新選擇協助者。從模擬結果，我們可以發現，不同的排程決策可適應在不同的車輛環境，並且動態比定期的重新選擇協同組有更好的效能。

When a vehicle requests a video stream from the Internet using the cellular network, i.e., 3G or 3.5G network, it may not have enough bandwidth to receive good quality of video. In order to resolve this problem, the vehicle is proposed to ask neighboring vehicles for the help of downloading the video stream using a short-range wireless technique, e.g., Dedicated Short Range Communications (DSRC). This scenario is called cooperative streaming in vehicular communications. Since the topology of vehicular networks changes rapidly, three critical issues in the moving vehicle-based cooperative streaming are (1) how to form a cooperative group dynamically, (2) how to schedule neighboring vehicles to help the video downloading process and (3) how to estimate the possible change of network conditions. This thesis proposes a mechanism called Cooperative Video Streaming over Vehicular Network (CVS-VN). The prediction Lifetime (PLT) is used to determine which neighboring vehicles can help the video downloading. The quality of streaming is improved when receiving the extra video data forwarded from neighbors' DSRC links. From the simulation results, we can find that different scheduling schemes are adaptive to different scenarios, and the proposed dynamic reformation scheme has better performance than periodic reformation.

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