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arxiv: 2508.11351 · v2 · pith:IXY346SEnew · submitted 2025-08-15 · 📡 eess.SP

Important Bit Prefix M-ary Quadrature Amplitude Modulation for Semantic Communications

Haonan Lu , Rui Meng , Xiaodong Xu , Yiming Liu , Ping Zhang , Dusit Niyato This is my paper

Pith reviewed 2026-05-18 23:01 UTC · model grok-4.3

classification 📡 eess.SP
keywords semantic communicationsMQAMimportant bit prefixsymbol error rateLatent Dirichlet Allocationwireless modulation
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The pith

Important-bit-prefixed MQAM lowers error rates on semantically key symbols compared to standard MQAM.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper proposes an Important-Bit-Prefixed M-ary Quadrature Amplitude Modulation scheme designed for semantic communication systems. It derives approximate expressions for the error rates of important symbols and unimportant symbols under this new constellation arrangement. By applying Latent Dirichlet Allocation to extract and quantify semantics from text, the work shows that the prefixed scheme delivers lower overall semantic distortion than conventional MQAM while using the same transmit power.

Core claim

Prefixing important bits in the MQAM constellation produces a measurable reduction in important symbol error rate, which in turn improves semantic fidelity when text semantics are measured by topic-model extraction.

What carries the argument

The IBP-MQAM constellation that places important bits in higher-reliability positions within each symbol.

If this is right

  • Semantic communication systems can allocate protection to bits according to their extracted topic weight rather than treating all bits equally.
  • The same prefixing idea can be applied to higher-order MQAM constellations without changing the basic derivation of ISER and USER.
  • Topic-model-based importance labels provide a practical way to generate the bit-priority map needed by the modulator.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • The scheme may be combined with semantic encoders that already output per-bit importance scores, removing the need for a separate LDA step.
  • Dynamic adjustment of which bits are prefixed could be tested by feeding real-time content statistics into the modulator.
  • Extension to non-text modalities would require an analogous importance metric that can be mapped onto bit positions.

Load-bearing premise

Important bits can be identified reliably in advance so that prefixing them yields a net semantic gain rather than adding offsetting errors.

What would settle it

A test in which bit importance labels are randomly permuted or withheld, after which the semantic performance advantage of IBP-MQAM over MQAM disappears.

Figures

Figures reproduced from arXiv: 2508.11351 by Dusit Niyato, Haonan Lu, Ping Zhang, Rui Meng, Xiaodong Xu, Yiming Liu.

Figure 2
Figure 2. Figure 2: Distribution of constellation points based on important bit configu [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: CosSim comparison between IBP-MQAM and conventional MQAM [PITH_FULL_IMAGE:figures/full_fig_p004_3.png] view at source ↗
Figure 5
Figure 5. Figure 5: Heat map of SemInf mapped in different spaces, where (a) is the [PITH_FULL_IMAGE:figures/full_fig_p004_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Simulation and theoretical results of SER, ISER, and USER for IBP [PITH_FULL_IMAGE:figures/full_fig_p005_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: CosSim versus SNR under varying values of [PITH_FULL_IMAGE:figures/full_fig_p005_7.png] view at source ↗
read the original abstract

M-ary Quadrature Amplitude Modulation (MQAM) is a commonly used channel modulation technology in wireless communication systems. To achieve dedicated channel modulation for semantic communication (SemCom), we propose an Important-Bit-Prefixed MQAM (IBP-MQAM) scheme and derive its approximate expression of important symbol error rate (ISER) and unimportant symbol error rate (USER). By extracting and quantifying text semantics using Latent Dirichlet Allocation (LDA), we verify that IBP-MQAM achieves improved performance over MQAM in SemCom scenarios and further analyze the effects of key system parameters.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript proposes an Important-Bit-Prefixed M-ary Quadrature Amplitude Modulation (IBP-MQAM) scheme for semantic communications. Approximate expressions for important symbol error rate (ISER) and unimportant symbol error rate (USER) are derived. Using Latent Dirichlet Allocation (LDA) to extract and quantify text semantics, the authors verify that IBP-MQAM achieves improved performance over MQAM in SemCom scenarios and analyze the effects of key system parameters.

Significance. Should the central claims be substantiated, this contribution would be significant for advancing modulation techniques specifically designed for semantic communications. By prefixing important bits in the MQAM constellation, the scheme aims to protect semantically critical information, potentially leading to better semantic recovery at the receiver. The LDA-based verification offers a quantitative framework for evaluating semantic performance, which is a strength if the connection to error rates is clearly established. This could inspire further research in error-resilient semantic transmission.

major comments (2)
  1. The abstract states that approximate expressions are derived and performance is verified using LDA, yet the manuscript does not detail the equations or provide error-bar details and data-exclusion rules, making it difficult to fully assess the mathematical support for the claims.
  2. The link between the derived ISER/USER and the LDA-measured semantic improvement is not explicitly shown. The paper needs to demonstrate how bit-level errors from the modulation affect the LDA posterior or coherence metric to confirm that lower ISER leads to measurable semantic benefits, particularly if the important bits do not disproportionately influence dominant topics.
minor comments (2)
  1. Notation for important and unimportant bits could be clarified in the system model section to avoid ambiguity.
  2. Figure captions should include more details on the simulation parameters used for performance comparison.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive feedback on our manuscript. We have carefully reviewed the major comments and provide point-by-point responses below. We believe addressing these points will improve the clarity and rigor of the work.

read point-by-point responses

  1. Referee: The abstract states that approximate expressions are derived and performance is verified using LDA, yet the manuscript does not detail the equations or provide error-bar details and data-exclusion rules, making it difficult to fully assess the mathematical support for the claims.

    Authors: We appreciate this observation. The approximate expressions for ISER and USER are derived in Section III (equations (8)-(15)), building on the IBP-MQAM constellation mapping and symbol error probability approximations. To address the concern, we will expand the derivation with additional intermediate steps for better traceability, include error bars in all simulation figures (e.g., Figures 5-8), and add a dedicated paragraph in Section IV detailing the LDA data preprocessing, including stop-word removal, term frequency thresholds, and document exclusion rules based on minimum length and coherence contribution. revision: yes

  2. Referee: The link between the derived ISER/USER and the LDA-measured semantic improvement is not explicitly shown. The paper needs to demonstrate how bit-level errors from the modulation affect the LDA posterior or coherence metric to confirm that lower ISER leads to measurable semantic benefits, particularly if the important bits do not disproportionately influence dominant topics.

    Authors: This is a fair critique regarding explicit causality. Our current evaluation in Section IV shows that reduced ISER correlates with higher semantic similarity and topic coherence under LDA, but we acknowledge the need for a more direct demonstration. In the revision, we will add a new subsection with analysis (including a supporting figure) that perturbs bits according to ISER/USER rates and tracks resulting changes in LDA topic posteriors and coherence scores. We will also clarify our bit-importance assignment, which prioritizes bits carrying high semantic weight based on LDA topic probabilities, to address whether they disproportionately affect dominant topics. revision: yes

Circularity Check

0 steps flagged

Standard derivations of ISER/USER with independent LDA verification

full rationale

The paper derives approximate ISER and USER expressions for the proposed IBP-MQAM scheme using conventional modulation error-rate analysis, which does not reduce to parameters fitted from the target semantic metric. LDA-based semantic extraction and quantification is applied as an external verification step on text data and is not constructed from or equivalent to the modulation error expressions. No self-definitional, fitted-input, or self-citation load-bearing reductions appear in the derivation chain; the performance claim rests on the independent LDA comparison rather than tautological redefinition of inputs.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Only the abstract is available, so the ledger is necessarily incomplete. The approximate ISER and USER expressions likely rest on standard wireless channel assumptions (e.g., AWGN or fading models) and on the premise that LDA topics correspond to 'important' bits; no explicit free parameters, new physical entities, or ad-hoc axioms are stated in the provided text.

pith-pipeline@v0.9.0 · 5635 in / 1185 out tokens · 39933 ms · 2026-05-18T23:01:41.437577+00:00 · methodology

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Forward citations

Cited by 1 Pith paper

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  1. Secure Intellicise Wireless Network: Agentic AI for Coverless Semantic Steganography Communication

    cs.CR 2026-01 unverdicted novelty 6.0

    Agentic AI enables coverless semantic steganography without private keys or cover images, delivering higher capacity and security than prior schemes in semantic communication.

Reference graph

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