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arXiv 1708.04778cs.ITmath.IT
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任意信源高斯码本率失真的改进渐近性

Refined Asymptotics for Rate-Distortion using Gaussian Codebooks for Arbitrary Sources

Lin Zhou, Vincent Y. F. Tan, Mehul Motani

摘要:

Lapidoth(1997)所考虑的率失真鞍点问题在于当被约束为使用随机高斯码本并且采用最小(欧几里德)距离编码时,找到压缩任意遍历源的最小速率。在本文中,我们扩展了Lapidoth的分析在几个方向。首先,我们考虑精化渐近性。特别是,当源是平稳和无记忆的,我们建立了二阶,中等,大偏差渐近的问题。其次,Lapidoth通过“随机高斯码本”来指代随机码字的集合,每个随机码字独立且均匀地从$n$维球体的表面绘制。更准确地说,我们称之为球形码本。我们也考虑i.i.d.。高斯码本,其中每个随机码字独立于乘积高斯分布而绘制。我们推导出二阶、中等和大偏差渐近时,i.i.d.\采用高斯码本。与Scarlett,Tan和Durisi(2017)最近关于信道编码对应物的工作相反,球形和i.i.d.\高斯码本是相同的。我们给出了球面和i.i.d.的系综过度失真指数。为所有速率建立高斯码本。此外,我们还证明了i.i.d.\高斯码本有一个严格更大的过度失真指数比球面对应的任何速率大于合奏率失真函数由Lapidoth。

英文摘要:

The rate-distortion saddle-point problem considered by Lapidoth (1997) consists in finding the minimum rate to compress an arbitrary ergodic source when one is constrained to use a random Gaussian codebook and minimum (Euclidean) distance encoding is employed. We extend Lapidoth's analysis in several directions in this paper. Firstly, we consider refined asymptotics. In particular, when the source is stationary and memoryless, we establish the second-order, moderate, and large deviation asymptotics of the problem. Secondly, by "random Gaussian codebook", Lapidoth referred to a collection of random codewords, each of which is drawn independently and uniformly from the surface of an $n$-dimensional sphere. To be more precise, we term this as a spherical codebook. We also consider i.i.d.\ Gaussian codebooks in which each random codeword is drawn independently from a product Gaussian distribution. We derive the second-order, moderate, and large deviation asymptotics when i.i.d.\ Gaussian codebooks are employed. In contrast to the recent work on the channel coding counterpart by Scarlett, Tan and Durisi (2017), the dispersions for spherical and i.i.d.\ Gaussian codebooks are identical. The ensemble excess-distortion exponents for both spherical and i.i.d.\ Gaussian codebooks are established for all rates. Furthermore, we show that the i.i.d.\ Gaussian codebook has a strictly larger excess-distortion exponent than its spherical counterpart for any rate greater than the ensemble rate-distortion function derived by Lapidoth.

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