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ABSTRACT: The two-channel multiple descriptions problem for an independent and identically distributed (i.i.d.) source, with feed-forward to one or both side-decoders is considered. A single-letter achievable rate-region is derived; it enlarges the best known rate-region for multiple descriptions without feed-forward. The proof of the result uses a block-Markov superposition source coding strategy. In point-to-point source coding, feed-forward does not decrease the rate-distortion function of an i.i.d. source. In contrast, an example is provided to show that the derived region can be strictly larger than the optimal multiple description rate-distortion region without feed-forward.
IEEE Transactions on Information Theory 05/2011; · 3.01 Impact Factor
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ABSTRACT: A single-letter achievable rate region is proposed for the two-receiver discrete memoryless broadcast channel with feedback. It is shown through an example that the rate-region can be strictly larger than the no-feedback capacity region. The coding strategy involves block-Markov superposition coding using Marton's scheme as the starting point. If the message rates in the Marton scheme are too high to be decoded at the end of a block, each receiver is left with a list of messages compatible with its output. In the next block, we send resolution information for each receiver to resolve its list. The key observation is that the resolution information of the first receiver is correlated with that of the second. We transmit this correlated information efficiently in the following block using ideas from the Han-Costa coding scheme.
Information Theory Proceedings (ISIT), 2010 IEEE International Symposium on; 07/2010
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ABSTRACT: Let X and Y be finite alphabets and P<sub>XY</sub> a joint distribution over them, with P<sub>X</sub> and P<sub>Y</sub> representing the marginals. For any ϵ > 0, the set of n-length sequences x<sup>n</sup> and y<sup>n</sup> that are jointly typical according to P<sub>XY</sub> can be represented on a bipartite graph. We present a formal definition of such a graph, known as a typicality graph, and study some of its properties. These properties arise in the study of several multiuser communication problems.
Information Theory Proceedings (ISIT), 2010 IEEE International Symposium on; 07/2010
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ABSTRACT: A single-letter achievable rate region for the two-user discrete memoryless multiple-access channel is proposed. The rate region includes the Cover-Leung region, and it is shown that the inclusion is strict. The proof uses a block-Markov superposition strategy based on the observation that the messages of the two users are correlated given the feedback. The rates of transmission are too high for each encoder to decode the other's message directly using the feedback, so they transmit correlated information in the next block in order to learn the message of one another. They then cooperate in the following block to resolve the residual uncertainty of the decoder. Our scheme may be viewed as a natural generalization of the Cover-Leung scheme with a delay of one extra block and a pair of additional auxiliary random variables. The scheme can also be extended to obtain larger rate-regions with more auxiliary random variables.
Information Theory, 2009. ISIT 2009. IEEE International Symposium on; 08/2009
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ABSTRACT: The two-channel multiple descriptions problem for an i.i.d source, with feed-forward to one or both side-decoders is considered. A single-letter achievable rate-region is derived; it enlarges the best known rate-region for multiple descriptions without feed-forward. The proof of the result uses a block-Markov superposition source coding strategy. In point-to-point source coding, feed-forward does not decrease the rate-distortion function of an i.i.d source. In contrast, an example is provided to show that the derived region can be larger than the optimal multiple description rate region without feed-forward.
Information Theory, 2008. ISIT 2008. IEEE International Symposium on; 08/2008
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ABSTRACT: In this work, we consider a source coding model with feed-forward. We analyze a system with a noiseless, feed-forward link where the decoder has knowledge of all previous source samples while reconstructing the present sample. The rate-distortion function for an arbitrary source with feed-forward is derived in terms of directed information, a variant of mutual information. We further investigate the nature of the rate-distortion function with feed-forward for two common types of sources- discrete memory- less sources and Gaussian sources. We then characterize the error exponent for a general source with feed-forward. The results are then extended to feed-forward with an arbitrary delay larger than the block length.
IEEE Transactions on Information Theory 07/2007; · 3.01 Impact Factor
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ABSTRACT: In this work, we consider a source coding model with feedforward. We analyze a system with a noiseless feedforward link where the decoder has knowledge of all previous source samples while reconstructing the present sample. The rate-distortion function for an arbitrary source with feedforward is derived in terms of directed information, a variant of mutual information. The special cases of discrete memoryless sources and Gaussian sources with feedforward are further examined. We also derive a random coding error exponent which is used to bound the probability of decoding error for a source code (with feedforward) of finite block length. The results are then extended to feedforward with an arbitrary delay larger than the block length.
Information Theory Workshop, 2004. IEEE; 11/2004
