可調適視訊壓縮串流在超寬頻無線技術WiMedia傳輸之低視訊延遲回報機制設計

Abstract

可調適視訊編碼(SVC)是可針對應用與頻寬變化需求，彈性的調整輸出位元組的視訊編碼技術，適合無線傳輸與網路變動頻寬的應用。超寬頻（‎Ultra-wideband，簡稱UWB）是一種具備低耗電與高速傳輸的無線通訊技術，適合需要高質量服務的無線通信應用，可以用在家庭網路連接和無線個人區域網路等領域。透過系統上跨層級的設計，使短距無線多媒體傳輸成為可能且更有彈性與效率。 在本論文中，我們考慮可調適視訊編碼與超寬頻MB-OFDM WiMedia的特性，在視訊傳輸端提出WiMedia媒介存取控制層(MAC layer)的一套系統架構包括跨層級的回報機制。透過WiMedia 媒介存取控制層監測頻寬來估計下一段時間可用頻寬並同時考慮解碼器緩衝區的延遲效應後回報，進而調整可調適視訊編碼所要傳送的位元組，以減少頻寬變動與無線通道品質的干擾。最後在系統層級上模擬所提出來的跨層架構以及頻寬回報機制對於播放延遲、頻寬使用率以及資料緩衝區所累積的資料大小的效能表現.。

Scalable Video Coding (SVC) is a video compression technology which can provide flexible bitstream extraction according to the requirements of application and network bandwidth. WiMedia Ultra-WideBand is a wireless communication technique which contains the characteristics of low power and high data-rate. It is suitable for the Wireless Personal Area Network (WPAN) and communication network at home. Thought the cross layer design makes the wireless multimedia transmission over short distance become not only possible but also more flexible and efficient. In this thesis, we proposed a cross-layer architecture including a feedback scheme which takes advantage of the characteristics of SVC and WiMedia, on the Medium Access Control (MAC) layer of transmitter. Thought the monitoring of bandwidth fluctuation by MAC layer, we can estimate the available bandwidth of next period and dynamically adjust the feedback extraction bitrate after considering the issue of video latency on the buffer of decoder in order to reduce the impact of the variation of network bandwidth and channel condition on real time video communication. Finally, with the proposed architecture and mechanism, we will simulate the performance of video latency, bandwidth utilization and buffer condition on WiMedia with SVC as our application in system level.