Achievable Refined Asymptotics for Successive Refinement Using Gaussian Codebooks

TL;DR

This paper analyzes the performance limits of Gaussian codebooks in the successive refinement source coding problem, deriving refined asymptotics and showing strong successiveness for a broad class of sources.

Contribution

It provides new achievable refined asymptotics for mismatched successive refinement with Gaussian codebooks, including second-order, moderate, and large deviations regimes, and proves strong successiveness for mild conditions.

Findings

Achievable second-order rate-region under joint excess-distortion probability.

Strong successiveness for mild source conditions.

Achievable exponents for large deviations with Gaussian codebooks.

Abstract

We study the mismatched successive refinement problem where one uses Gaussian codebooks to compress an arbitrary memoryless source with successive minimum Euclidean distance encoding under the quadratic distortion measure. Specifically, we derive achievable refined asymptotics under both the joint excess-distortion probability (JEP) and the separate excess-distortion probabilities (SEP) criteria. For both second-order and moderate deviations asymptotics, we consider two types of codebooks: the spherical codebook where each codeword is drawn independently and uniformly from the surface of a sphere and the i.i.d. Gaussian codebook where each component of each codeword is drawn independently from a Gaussian distribution. We establish the achievable second-order rate-region under JEP and we show that under SEP any memoryless source satisfying mild moment conditions is strongly successively refinable. When specialized to a Gaussian memoryless source (GMS), our results provide an alternative achievability proof with specific code design. We show that under JEP and SEP, the same moderate deviations constant is achievable. For large deviations asymptotics, we only consider the i.i.d. Gaussian codebook since the i.i.d. Gaussian codebook has better performance than the spherical codebook in this regime for the one layer mismatched rate-distortion problem (Zhou, Tan, Motani, TIT, 2019). We derive achievable exponents of both JEP and SEP and specialize our results to a GMS, which appears to be a novel result of independent interest.