Efficient Online WiFi Delivery of Layered-Coding Media Using Inter-layer Network Coding
Efficient Online WiFi Delivery of Layered-Coding Media Using Inter-layer Network Coding
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DOI：
10.1109/icdcs.2011.52
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发表时间：
2011-06
期刊：
影响因子：
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通讯作者：
Dimitrios Koutsonikolas;Y. C. Hu;Chih-Chun Wang;M. Comer;Amr Mahmoud;Salem Mohamed
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文献类型：
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作者：
Dimitrios Koutsonikolas;Y. C. Hu;Chih-Chun Wang;M. Comer;Amr Mahmoud;Salem Mohamed
在无线 LAN 中向多个客户端多播视频的主要挑战是处理客户端多样性 - 客户端可能具有不同的通道特性，因此从 AP 接收到不同数量的传输。克服这个问题的一个有前途的方法是将多分辨率（分层）视频编码与层间网络编码相结合。这种方法的基本挑战是确定跨不同层对数据包进行编码的策略，以最大化所有客户端的解码层数。本文做出了三点贡献。 (1) 我们首先表明，即使对于一个客户端，先前提出的用于层间网络编码的规范三角方案也可能表现不佳。我们展示了如何通过合并估计的目标层数来增强三角方案，从而显着提高其有效性。 （2）我们表明，这种增强的三角方案对于具有不同信道特征的多个客户端来说仍然表现不佳，这激发了搜索最佳编码策略的需要。搜索最优策略的简单方法在计算上是令人望而却步的。我们提出了几种优化方法，可以大大降低彻底搜索最佳策略的复杂性，使其实时可行。 (3) 最后，我们设计并评估了一种在线视频传输方案 Percy，该方案将部署在无线 LAN 的 AP 后面的代理处。我们的模拟结果表明，对于不同数量的客户端，Percy 的性能优于之前的层间编码启发式高达 22-80%。
A primary challenge in multi casting video in a wireless LAN to multiple clients is to deal with the client diversity -- clients may have different channel characteristics and hence receive different numbers of transmissions from the AP. A promising approach to overcome this problem is to combine multi-resolution (layered) video coding with interlayer network coding. The fundamental challenge in such an approach is to determine the strategy of coding the packets across different layers that maximizes the number of decoded layers at all clients. This paper makes three contributions. (1) We first show that even for one client, the previously proposed canonical triangular scheme for inter-layer network coding can perform poorly. We show how to enhance the triangular scheme by incorporating the estimated target number of layers which significantly improves its effectiveness. (2) We show that such an enhanced triangular scheme still performs poorly for multiple clients with diverse channel characteristics, which motivates the need for searching for the optimal coding strategy. The naive way of searching for the optimal strategy is computationally prohibitive. We present several optimizations that drastically reduce the complexity of exhaustively searching for the optimal strategy, making it feasible in real time. (3) Finally, we design and evaluate an on line video delivery scheme, Percy, to be deployed at a proxy behind the AP of a wireless LAN. Our simulation results show that Percy outperforms the previous inter-layer coding heuristic by up to 22-80% with varying numbers of clients.