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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

On Optimum Conventional Quantization for Source Coding with Side Information at the Decoder

Zheng, Lin January 2007 (has links)
In many scenarios, side information naturally exists in point-to-point communications. Although side information can be present in the encoder and/or decoder and thus yield several cases, the most important case that worths particular attention is source coding with side information at the decoder (Wyner-Ziv coding) which requires different design strategies compared to the the conventional source coding problem. Due to the difficulty caused by the joint design of random variable and reconstruction function, a common approach to this lossy source coding problem is to apply conventional vector quantization followed by Slepian-Wolf coding. In this thesis, we investigate the best rate-distortion performance achievable asymptotically by practical Wyner-Ziv coding schemes of the above approach from an information theoretic viewpoint and a numerical computation viewpoint respectively.From the information theoretic viewpoint, we establish the corresponding rate-distortion function $\hat{R}_{WZ}(D)$ for any memoryless pair $(X,Y)$ and any distortion measure. Given an arbitrary single letter distortion measure $d$, it is shown that the best rate achievable asymptotically under the constraint that $X$ is recovered with distortion level no greater than $D \geq 0$ is $\hat{R}_{WZ}(D) = \min_{\hat{X}} [I(X; \hat{X}) - I(Y; \hat{X})]$, where the minimum is taken over all auxiliary random variables $\hat{X}$ such that $Ed(X, \hat{X}) \leq D$ and $\hat{X}\to X \to Y$ is a Markov chain.Further, we are interested in designing practical Wyner-Ziv coding. With the characterization at $\hat{R}_{WZ}(D)$, this reduces to investigating $\hat{X}$. Then from the viewpoint of numerical computation, the extended Blahut-Arimoto algorithm is proposed to study the rate-distortion performance, as well as determine the random variable $\hat{X}$ that achieves $\hat{R}_{WZ}(D)$ which provids guidelines for designing practical Wyner-Ziv coding.In most cases, the random variable $\hat{X}$ that achieves $\hat{R}_{WZ}(D)$ is different from the random variable $\hat{X}'$ that achieves the classical rate-distortion $R(D)$ without side information at the decoder. Interestingly, the extended Blahut-Arimoto algorithm allows us to observe an interesting phenomenon, that is, there are indeed cases where $\hat{X} = \hat{X}'$. To gain deep insights of the quantizer's design problem between practical Wyner-Ziv coding and classic rate-distortion coding schemes, we give a mathematic proof to show under what conditions the two random quantizers are equivalent or distinct. We completely settle this problem for the case where ${\cal X}$, ${\cal Y}$, and $\hat{\cal X}$ are all binary with Hamming distortion measure.We also determine sufficient conditions (equivalent condition) for non-binary alphabets with Hamming distortion measure case and Gaussian source with mean-squared error distortion measure case respectively.
2

On Optimum Conventional Quantization for Source Coding with Side Information at the Decoder

Zheng, Lin January 2007 (has links)
In many scenarios, side information naturally exists in point-to-point communications. Although side information can be present in the encoder and/or decoder and thus yield several cases, the most important case that worths particular attention is source coding with side information at the decoder (Wyner-Ziv coding) which requires different design strategies compared to the the conventional source coding problem. Due to the difficulty caused by the joint design of random variable and reconstruction function, a common approach to this lossy source coding problem is to apply conventional vector quantization followed by Slepian-Wolf coding. In this thesis, we investigate the best rate-distortion performance achievable asymptotically by practical Wyner-Ziv coding schemes of the above approach from an information theoretic viewpoint and a numerical computation viewpoint respectively.From the information theoretic viewpoint, we establish the corresponding rate-distortion function $\hat{R}_{WZ}(D)$ for any memoryless pair $(X,Y)$ and any distortion measure. Given an arbitrary single letter distortion measure $d$, it is shown that the best rate achievable asymptotically under the constraint that $X$ is recovered with distortion level no greater than $D \geq 0$ is $\hat{R}_{WZ}(D) = \min_{\hat{X}} [I(X; \hat{X}) - I(Y; \hat{X})]$, where the minimum is taken over all auxiliary random variables $\hat{X}$ such that $Ed(X, \hat{X}) \leq D$ and $\hat{X}\to X \to Y$ is a Markov chain.Further, we are interested in designing practical Wyner-Ziv coding. With the characterization at $\hat{R}_{WZ}(D)$, this reduces to investigating $\hat{X}$. Then from the viewpoint of numerical computation, the extended Blahut-Arimoto algorithm is proposed to study the rate-distortion performance, as well as determine the random variable $\hat{X}$ that achieves $\hat{R}_{WZ}(D)$ which provids guidelines for designing practical Wyner-Ziv coding.In most cases, the random variable $\hat{X}$ that achieves $\hat{R}_{WZ}(D)$ is different from the random variable $\hat{X}'$ that achieves the classical rate-distortion $R(D)$ without side information at the decoder. Interestingly, the extended Blahut-Arimoto algorithm allows us to observe an interesting phenomenon, that is, there are indeed cases where $\hat{X} = \hat{X}'$. To gain deep insights of the quantizer's design problem between practical Wyner-Ziv coding and classic rate-distortion coding schemes, we give a mathematic proof to show under what conditions the two random quantizers are equivalent or distinct. We completely settle this problem for the case where ${\cal X}$, ${\cal Y}$, and $\hat{\cal X}$ are all binary with Hamming distortion measure.We also determine sufficient conditions (equivalent condition) for non-binary alphabets with Hamming distortion measure case and Gaussian source with mean-squared error distortion measure case respectively.

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