車載群播網路多媒體串流封包補傳最佳時間延遲演算法

Delay-Guarantee Chunk Reloading for Real-Time Multicasting in VANET Network

劉政昕(Cheng-Hsin Liu)

指導教授 ： 張本杰

朝陽科技大學/資訊學院/資訊工程系/碩士(2010年)

摘要

Vehicular Adhoc Networks(VANet)車載網路系統環境中，提供了多媒體影音服務是未來的趨勢，因此發展出Real-time Video Streaming的協定來傳送影像封包，隨著影音的品質提升，對於無線網路環境下傳送封包的Delay time 和Packet lost rate更嚴謹。為了節省頻寬與具有服務品質保證(Quality of services)，Multicast 來傳送封包，使用者在接收Video streaming封包時候，因為頻寬不足、無線傳輸干擾等因素，造成封包的遺失與嚴重封包延遲，Real-time Video Streaming又要求Delay time不能超過200ms，可能會造成影像中斷或服務品質下降等缺點，因此，在VANet無線網路連線品質不佳與不穩定的網路中，很難達成符合QoS的Multicast streaming服務。因此我們提出這篇論文在VANet的環境形成Vehicle-to-vehicle(V2V)的特性，提出Delay-Guarantee P2P Algorithm(DGPA)以VANet Multicasting為基礎，對streaming packet遺失的接收節點，提出peer-to-peer應用重疊網路(P2P Application overlay Network)選擇最佳的peer來補償packet loss運作，並且考量傳送的延遲時間，來達到Real-time streaming 的服務品質要求；數據顯示，我們所提的Multicast streaming P2P補償方法在(1)chunk救援成功率、(2)平均封包delay、(3)不符合QoS品質比率等表現，皆優於所比較的方法，其中，採用Multicast重傳與隨機選擇單點重傳，可能都會造成浪費頻寬以及傳送延遲時間過長，並且可能補傳中又發生遺失。而我們的方法，有效減少傳送的延遲時間，並且增加了補傳封包的成功率，來達到影音服務的最高品質。

關鍵字

即時多媒體 ； 車載網路 ； 群播傳送

並列摘要

One of the interesting trends in the future wireless mobile applications is to offer real-time video streaming service in Vehicular Adhoc Networks (VANETs). The specification of Real-Time Video Streaming for video chunk transmission is thus specified. As the video quality increasing, the constraints of packet delay, packet loss rate and the required bandwidth of packet transmission become more critically in VANET. Multicasting is thus adopted to reduce the bandwidth waste rate while a sender wants to send real-time videos to a group of receivers. In VANET, wireless interference and limited bandwidth easily lead to lost chunks and long chunk delay, and then significantly degrade network performance. Although the multicasting VANET can adopt the retransmission of lost chunks, it results in long multicasting delay and wastes bandwidth for re-sending video chunks to the receivers that have successfully received chunks. Therefore, this work proposes a P2P overlay network to cooperate with the multicast VANET, in which a Delay-Guarantee chunk Reloading mechanism (DGR) is adopted to reload the lost or unconfirmed chunks. In DGPA, a chunk with the least delay to the lost-chunk is selected as the optimal compensating result. Numerical results demonstrate that the proposed DGR approach outperforms the compared approaches in 1) successful chunk reload rate, 2) average chunk delay, and 3) unconfirmed-QoS chunk rate. Clearly, the retransmission-based multicasting and the random chunk-selection mechanism lead to long delay and high bandwidth waste rate. DGR minimizes the chunk compensation delay and bandwidth waste rate.

並列關鍵字

Vehicular adhoc networks ； Multicasting ； real-time video streaming

參考文獻

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