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总览 评价 王莉莎 ， 刘丹谱 * ， 张志龙 （ 北京邮电大学网络体系构建与融合北京市重点实验室，北京 100876； ） 摘要： 近年来无线视频组播技术受到人们广泛关注。传统的点对点传输方案要求发送端预知接收端信道条件并选择最佳的编码调制方案，但在组播场
王莉莎， 刘丹谱*， 张志龙
（
北京邮电大学网络体系构建与融合北京市重点实验室，北京 100876； ）
摘要：
近年来无线视频组播技术受到人们广泛关注。传统的点对点传输方案要求发送端预知接收端信道条件并选择最佳的编码调制方案，但在组播场景或移动场景下，这种方案将产生悬崖效应，即信噪比小于某一门限值后，接收质量急剧下降。SoftCast系统通过保证信道中传输的信号与原始像素值的线性关系解决了这一问题，使得接收效果只受接收端信道条件的影响。本文基于IEEE802.11a协议搭建SoftCast仿真平台，并针对3DDCT系数的分布规律提出了一种简化的对角视频块划分方案。该划分方式相比于传统均等划分方案，只需要传输少量的元数据，并且复杂度相对较低。仿真结果表明，在相同信道下传输相同数据量，对角划分方案可以将峰值信噪比提高约2dB。
关键词：
视频组播传输；SoftCast；简化视频块划分；3DDCT
Wang Lisha， Liu Danpu*， Zhang Zhilong
（
Beijing Key Laboratory of Network System Architecture and Convergence Beijing University of Posts and Telecommunications,Beijing 100876； ）
Abstract：
In recent years, wireless video broadcasting receives widespread attention, the conventional wireless system based on source and channel coding generally needs to know the channel parameters and choose the optimal coding and modulation scheme. However, in broadcast or mobile scenarios, the traditional method will lead to clift effect, once the signal-to-noise ratio falls below a threshold, the decoding process tends to break down sharply. Softcast makes a great improvement on this problem by keeping the linear repation between the pixels luminance and the signal transmitted on the channel, it ensure the decoding quality only influenced by the receiver's channel condition. In this paper,we simulate the SoftCast scheme base on IEEE802.11a protocal, and proposed a simplfied diagonal chunk division method according to the distribution of 3DDCT coefficients. This method transfers less metadata and consumpts less time. Expertimental results show that the proposed scheme can improve the performance of the original SoftCast by almost 2dB, using the same number of metadata and lower time consumption.
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