隨著車載網路的迅速發展，3G/3.5G以及車間專用短程通信技術(DSRC)實現了針對車載網路的新型態網路服務。考慮在車載網路中進行多媒體影片串流，單一行進車輛中的使用者利用其3G/3.5G網路可能無法擁有足夠支援高品質影片串流的頻寬。針對以上的考慮，本篇論文的動機為研究如何在以車隊為基礎的車載網路環境中進行合作式的影片串流。在車隊中，當一輛車需要經過3G/3.5G網路連上Internet要求影片串流，這台車輛可以同時藉由鄰近的其他車隊成員們下載所需要的影片串流。接著，這些鄰近的車隊成員們可以利用車間專用短程通信技術將所下載的資料傳送給需要影片串流的這台車輛。在本篇論文中提出了兩個鄰近幫載成員選擇法(helper selection algorithms)在許多車隊成員中挑選適合的成員幫忙下載影片串流。當決定幫載成員(helper)後，利用所設計的兩個影片片段分配法(video assignment algorithms)將不同的影片片段排程到不同的幫載成員上。此外，為了區分隨著時間而持續由3G/3.5G以及DSRC兩段無線網路所造成的影響，一個緩衝區動態消脹感知排程技術被設計來根據影片需求者的緩衝區影片撥放長度在車載網路下的動態變化，調整串流的排程而滿足影片需求者的服務品質(QoS)。為了模擬車載網路中以車隊為基礎的合作式H.264/SVC可調式視訊串流，在NS-2的模擬環境中我們設計了一個在高速公路上車隊的移動模式，並且利用H.264/SVC作為影片編解碼技術。模擬的結果顯示在隨著不同的高速公路的交通情況以及隨時間改變的DSRC以及3G/3.5G網路環境中，影片片段分配法能夠區分不同的影片片段的優先順序以及重要性。在這裡所提出的影片片段分配法可以在不同的交通狀況以及網路狀況中保護較重要的H.264/SVC影片加強層，進而改善整體影片的品質。另外，緩衝區動態消脹感知的作法可以透過動態調整所要求的影片加強層以及幫載節點的集合，進而對網路的變化進行即時的反應。根據實驗結果，透過整合適當的影片片段分配法以及緩衝區動態消脹感知排程技術，可以在車載網路中提升影片品質。

The rapid development of vehicular communications, e.g., 3G/3.5G and Dedicated Short Range Communication (DSRC), realizes new types of network services for automotive use. Regarding multimedia streaming services, a vehicle may not have enough bandwidth to receive good quality of video using 3G/3.5G network. Hence, the motivation of this thesis is to investigate the fleet-based cooperative streaming scenario over the vehicular environment. When a vehicle requests a video stream from the Internet using 3G/3.5G network, it asks neighboring members belonging to the same fleet to download the requested video data simultaneously. Then, neighboring members forward video data to the requesting vehicle for quality improvement using DSRC network. In this thesis, two helper selection algorithms are proposed to select helpers among several members that belong to the same fleet. After determining helper candidates, two video assignment algorithms are designed to schedule each helper to download parts of video data. Besides, the differentiation between these two wireless networks, i.e., 3G/3.5G and DSRC, are varying with time. A buffer-aware scheduling mechanism is proposed to satisfy the requester’s QoS based on the requester’s buffer status over the dynamic variation of vehicular networks. In order to simulate the fleet-based cooperative H.264/SVC streaming over vehicular network, we designed the mobility pattern of a fleet on the highway in the NS-2 simulation environment, and adopted the H.264/SVC as the video coding technique. With different highway traffic conditions and the varying network conditions of DSRC and 3G/3.5G network, the video assignment algorithm takes the priority and importance of different enhancement layer into consideration. The proposed assignment can improve the video quality over different traffic and network conditions by protecting more important layers. Furthermore, the buffer-aware scheduling mechanism provides instantaneous reaction to the change of the network condition by adjusting the video quality and the helper set dynamically. Thus, from the experiment results, with the integration of the appropriate video assignment algorithm and the buffer-aware scheduling mechanism, video quality can be improved in the vehicular network condition.

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