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Visual Media Coding and Transmission by Ahmet Kondoz

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9.3 Link Adaptation for Video Services

(Portion reprinted, with permission, from H. Kodikara, S.T. Worrall, A.M. Kondoz, A.H. Sadka, “Combined adaptive spreading gain control and unequal error protection for real-time video communications over WCDMA System”, 5th Int. Workshop on Image Analysis for Multimedia Interactive Services (WIAMIS'2004), Lisbon, Portugal, 21–23 April 2004. ©2004 IEEE.)

The previous sections investigated the performance of video in error-prone environments. The time-varying channel conditions resulting from the mobility of the terminal and the surroundings were not considered. The effects of time-varying channel conditions (slow-fading) on video performance and the techniques that can be used to mitigate these effects are investigated in this section. A performance enhancement method for real-time video communications employing link adaptation is discussed. A novel link-adaptation algorithm, which is based on feedback channel information including BLER, received signal strength (RSS), and the first-order statistic of the RSS is proposed and analyzed. Two approaches for link adaptation are investigated. First, the effects of a link-adaptation scheme at the video frame level, which aims to optimize video quality by varying the channel-coding scheme and video source rate for a fixed channel allocation, is studied. Second, a link-adaptation algorithm with a goal of maximizing the overall access network throughput is developed at the radio block level. Another ...

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