License: Creative Commons Attribution 4.0 International license (CC BY 4.0)
When quoting this document, please refer to the following
DOI: 10.4230/LIPIcs.APPROX/RANDOM.2022.17
URN: urn:nbn:de:0030-drops-171393
URL: http://dagstuhl.sunsite.rwth-aachen.de/volltexte/2022/17139/
Go to the corresponding LIPIcs Volume Portal

Duursma, Iwan ; Gabrys, Ryan ; Guruswami, Venkatesan ; Lin, Ting-Chun ; Wang, Hsin-Po

Accelerating Polarization via Alphabet Extension

pdf-format:
LIPIcs-APPROX17.pdf (0.7 MB)

Abstract

Polarization is an unprecedented coding technique in that it not only achieves channel capacity, but also does so at a faster speed of convergence than any other technique. This speed is measured by the "scaling exponent" and its importance is three-fold. Firstly, estimating the scaling exponent is challenging and demands a deeper understanding of the dynamics of communication channels. Secondly, scaling exponents serve as a benchmark for different variants of polar codes that helps us select the proper variant for real-life applications. Thirdly, the need to optimize for the scaling exponent sheds light on how to reinforce the design of polar code.
In this paper, we generalize the binary erasure channel (BEC), the simplest communication channel and the protagonist of many polar code studies, to the "tetrahedral erasure channel" (TEC). We then invoke Mori-Tanaka’s 2 × 2 matrix over ?_4 to construct polar codes over TEC. Our main contribution is showing that the dynamic of TECs converges to an almost-one-parameter family of channels, which then leads to an upper bound of 3.328 on the scaling exponent. This is the first non-binary matrix whose scaling exponent is upper-bounded. It also polarizes BEC faster than all known binary matrices up to 23 × 23 in size. Our result indicates that expanding the alphabet is a more effective and practical alternative to enlarging the matrix in order to achieve faster polarization.

BibTeX - Entry

@InProceedings{duursma_et_al:LIPIcs.APPROX/RANDOM.2022.17,
  author =	{Duursma, Iwan and Gabrys, Ryan and Guruswami, Venkatesan and Lin, Ting-Chun and Wang, Hsin-Po},
  title =	{{Accelerating Polarization via Alphabet Extension}},
  booktitle =	{Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2022)},
  pages =	{17:1--17:15},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-249-5},
  ISSN =	{1868-8969},
  year =	{2022},
  volume =	{245},
  editor =	{Chakrabarti, Amit and Swamy, Chaitanya},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/opus/volltexte/2022/17139},
  URN =		{urn:nbn:de:0030-drops-171393},
  doi =		{10.4230/LIPIcs.APPROX/RANDOM.2022.17},
  annote =	{Keywords: polar code, scaling exponent}
}

Keywords: polar code, scaling exponent
Collection: Approximation, Randomization, and Combinatorial Optimization. Algorithms and Techniques (APPROX/RANDOM 2022)
Issue Date: 2022
Date of publication: 15.09.2022

DROPS-Home | Fulltext Search | Imprint | Privacy Published by LZI