On the degradations of Binary-Input Discrete Memoryless Channels

Fuente: arXiv
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Main Authors: Jiao, Yadong, Cheng, Xiaoyan, Tang, Yuansheng, Xu, Ming
Format: Preprint
Published: 2026
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author Jiao, Yadong
Cheng, Xiaoyan
Tang, Yuansheng
Xu, Ming
author_facet Jiao, Yadong
Cheng, Xiaoyan
Tang, Yuansheng
Xu, Ming
contents For the polar codes introduced by Arikan in 2009, the first code family achieving the capacity of binary-input discrete memoryless channels (BIDMCs) with low-complexity encoding and decoding, it is crucial to evaluate the reliability of the synthetic channels resulted in the code construction. Since the synthetic channels have an output alphabet that grows exponentially with the code length, an effective method for faithfully evaluating their reliability is to replace them with degradations of manageable alphabet size. The main aim of this paper is to find the optimal degradations of symmetric BIDMCs. We determine all the degradations with the minimum probability of error decoding and give a necessary condition for the degradations with the maximum symmetric capacity. Finally, based on this necessary condition, we propose an efficient algorithm for finding degradation schemes that maximize the symmetric capacity.
format Preprint
id arxiv_https___arxiv_org_abs_2604_25552
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle On the degradations of Binary-Input Discrete Memoryless Channels
Jiao, Yadong
Cheng, Xiaoyan
Tang, Yuansheng
Xu, Ming
Information Theory
For the polar codes introduced by Arikan in 2009, the first code family achieving the capacity of binary-input discrete memoryless channels (BIDMCs) with low-complexity encoding and decoding, it is crucial to evaluate the reliability of the synthetic channels resulted in the code construction. Since the synthetic channels have an output alphabet that grows exponentially with the code length, an effective method for faithfully evaluating their reliability is to replace them with degradations of manageable alphabet size. The main aim of this paper is to find the optimal degradations of symmetric BIDMCs. We determine all the degradations with the minimum probability of error decoding and give a necessary condition for the degradations with the maximum symmetric capacity. Finally, based on this necessary condition, we propose an efficient algorithm for finding degradation schemes that maximize the symmetric capacity.
title On the degradations of Binary-Input Discrete Memoryless Channels
topic Information Theory
url https://arxiv.org/abs/2604.25552