86,533 research outputs found

    Variable-length compression allowing errors

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    This paper studies the fundamental limits of the minimum average length of lossless and lossy variable-length compression, allowing a nonzero error probability ϵ\epsilon, for lossless compression. We give non-asymptotic bounds on the minimum average length in terms of Erokhin's rate-distortion function and we use those bounds to obtain a Gaussian approximation on the speed of approach to the limit which is quite accurate for all but small blocklengths: (1−ϵ)kH(S)−kV(S)2πe−(Q−1(ϵ))22(1 - \epsilon) k H(\mathsf S) - \sqrt{\frac{k V(\mathsf S)}{2 \pi} } e^{- \frac {(Q^{-1}(\epsilon))^2} 2 } where Q−1(⋅)Q^{-1}(\cdot) is the functional inverse of the standard Gaussian complementary cdf, and V(S)V(\mathsf S) is the source dispersion. A nonzero error probability thus not only reduces the asymptotically achievable rate by a factor of 1−ϵ1 - \epsilon, but this asymptotic limit is approached from below, i.e. larger source dispersions and shorter blocklengths are beneficial. Variable-length lossy compression under an excess distortion constraint is shown to exhibit similar properties

    Cross layer techniques for flexible transport protocol using UDP-Lite over a satellite network

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    Traditional real-time multimedia and streaming services have utilised UDP over RTP. Wireless transmission, by its nature, may introduce a variable, sometimes high bit error ratio. Current transport layer protocols drop all corrupted packets, in contrast, protocols such as UDP-Lite allow error-resilient applications to be supported in the networking stack. This paper presents experimental quantitative performance metrics using H.264 and UDP Lite for the next generation transport of IP multimedia, and discusses the architectural implications for enhancing performance of a wireless and/or satellite environment

    Iterative Slepian-Wolf Decoding and FEC Decoding for Compress-and-Forward Systems

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    While many studies have concentrated on providing theoretical analysis for the relay assisted compress-and-forward systems little effort has yet been made to the construction and evaluation of a practical system. In this paper a practical CF system incorporating an error-resilient multilevel Slepian-Wolf decoder is introduced and a novel iterative processing structure which allows information exchanging between the Slepian-Wolf decoder and the forward error correction decoder of the main source message is proposed. In addition, a new quantization scheme is incorporated as well to avoid the complexity of the reconstruction of the relay signal at the final decoder of the destination. The results demonstrate that the iterative structure not only reduces the decoding loss of the Slepian-Wolf decoder, it also improves the decoding performance of the main message from the source
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