Poset-Markov Channels: Capacity via Group Symmetry

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Main Authors: Atay, Eray Unsal, Levin, Eitan, Chandrasekaran, Venkat, Kostina, Victoria
Format: Preprint
Published: 2025
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author Atay, Eray Unsal
Levin, Eitan
Chandrasekaran, Venkat
Kostina, Victoria
author_facet Atay, Eray Unsal
Levin, Eitan
Chandrasekaran, Venkat
Kostina, Victoria
contents Computing channel capacity is in general intractable because it is given by the limit of a sequence of optimization problems whose dimensionality grows to infinity. As a result, constant-sized characterizations of feedback or non-feedback capacity are known for only a few classes of channels with memory. This paper introduces poset-causal channels$\unicode{x2014}$a new formalism of a communication channel in which channel inputs and outputs are indexed by the elements of a partially ordered set (poset). We develop a novel methodology that allows us to establish a single-letter upper bound on the feedback capacity of a subclass of poset-causal channels whose memory structure exhibits a Markov property and symmetry. The methodology is based on symmetry reduction in optimization. We instantiate our method on two channel models: the Noisy Output is The STate (NOST) channel$\unicode{x2014}$for which the bound is tight$\unicode{x2014}$and a new two-dimensional extension of it.
format Preprint
id arxiv_https___arxiv_org_abs_2506_19305
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Poset-Markov Channels: Capacity via Group Symmetry
Atay, Eray Unsal
Levin, Eitan
Chandrasekaran, Venkat
Kostina, Victoria
Information Theory
Optimization and Control
Computing channel capacity is in general intractable because it is given by the limit of a sequence of optimization problems whose dimensionality grows to infinity. As a result, constant-sized characterizations of feedback or non-feedback capacity are known for only a few classes of channels with memory. This paper introduces poset-causal channels$\unicode{x2014}$a new formalism of a communication channel in which channel inputs and outputs are indexed by the elements of a partially ordered set (poset). We develop a novel methodology that allows us to establish a single-letter upper bound on the feedback capacity of a subclass of poset-causal channels whose memory structure exhibits a Markov property and symmetry. The methodology is based on symmetry reduction in optimization. We instantiate our method on two channel models: the Noisy Output is The STate (NOST) channel$\unicode{x2014}$for which the bound is tight$\unicode{x2014}$and a new two-dimensional extension of it.
title Poset-Markov Channels: Capacity via Group Symmetry
topic Information Theory
Optimization and Control
url https://arxiv.org/abs/2506.19305