提升H.264視訊傳輸品質於異質性網路

近年來，網際網路的普及化，帶動了許多網路多媒體服務。由於頻寬可能不足以應付多媒體傳輸時的龐大資料量，故服務品質保證(Quality of Service, QoS)是非常重要的議題。在異質性網路中的視訊服務品質保證，可區分為有線網域與無線網域，分別可以利用差異性網路(DiffServ Domain)與IEEE 802.11e提供資料封包的服務品質保證，本論文將整合這兩種網域，提升整體H.264視訊封包的傳輸品質。當視訊封包傳送到有線網路中，利用差異性網域將封包歸類為數種等級，以圖框間之結構不相似性(Structural Dissimilarity, SSIM)做為封包重要性之顏色標記依據，再經由存取點(Access Point, AP)，透過增強型分散式通道存取(Enhanced Distributed Channel Access, EDCA)，傳送到IEEE 802.11e之無線網域，並且利用封包檔頭(Header)中的結構不相似性與顏色之資訊進行佇列管理，將重要的視訊封包分配到優先權高的存取類別(Access Category, AC)佇列，減少其遺失的可能性。最後以NS2 (Network Simulator, Version 2)網路模擬平台下做實際模擬，利用背景訊流與視訊封包互相競逐，產生網路壅塞之現象模擬視訊畫面的遺失，以錯誤隱藏之機制遮隱遺失之畫面，並驗證本論文針對視訊傳輸品質提升之改良方法。

關鍵字

服務品質(QoS) ；差異性網域(DiffServ Domain) ； IEEE 802.11e ；增強型分散式通道存取(EDCA) ；網路模擬器2(NS2)

並列摘要

Multimedia network services are getting more prosperous than before as the Internet gradually becomes ubiquitously accessible. Since multimedia transmission could easily demand a considerable amount of bandwidth much more than the channel capacity, the Quality of Service (QoS) becomes an important issue. In the heterogeneous network, both frameworks of the DiffServ domain for wired network and the IEEE 802.11e domain for wireless network can guarantee the QoS service. In this thesis, we will integrate these two domains to improve the overall quality for H.264 video packet transmission. In DiffServ Domain of the wired network, we categorize the video packet into several QoS levels by marking different colors according to the structural dissimilarity between video frames. When these packets are delivered to the Access point (AP) of the IEEE 802.11e wireless network, The AP will examine the packet color value and the structural dissimilarity value from the packet header, and forwards the more important packet to the corresponding higher priority AC queue, to reduce the possibility of losing important video contents. NS-2 network simulator is used as our test-bed, for constructing a congested network and simulating the video packet loss with error concealment at decoder, to show that the transmitted video quality is improved.

並列關鍵字

Quality of Service ； DiffServ Domain ； IEEE 802.11e ； EDCA ； NS2

參考文獻

[9] J. Postel, “Internet Protocol,” IETF RFC 791, 1981.

[10] S. Deering and R. Hinden, “Internet Protocol, Version 6 (IPv6) Specification,” IETF RFC 2460, 1998.

[16] S. Floyd and V. Jacobson, “Random early detection gateways for congestion avoidance,” IEEE/ACM Transactions on Networking, Vol. 1, Issue 4, pp.397-413, Aug. 1993.

[17] D. Clark and W. J. Fang, “Explicit allocation of best-effort packet delivery service,” IEEE/ACM Transactions on Networking, Vol. 6, Issue 4, pp. 362-373, Aug. 1998.

[22] Y. L. Xu and Y. H. Zhou, “H.264 video communication based refined error concealment schemes,” IEEE Transactions on Consumer Electronics, Vol. 50, Issue 4, pp. 1135-1141, Nov. 2004.

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提升H.264視訊傳輸品質於異質性網路

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