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arxiv: 1907.07269 · v1 · pith:MA5A7TNVnew · submitted 2019-07-16 · 💻 cs.IT · math.IT

Scalar Quantizer Design for Two-Way Channels

Saeed Rezazadeh , Fady Alajaji , Wai-Yip Chan This is my paper

Pith reviewed 2026-05-24 20:24 UTC · model grok-4.3

classification 💻 cs.IT math.IT
keywords two-way channelsscalar quantizationcorrelated sourceslossy transmissionfull-duplexinterference mitigationGaussian sourcessignal-to-distortion ratio
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The pith

A full-duplex channel-optimized scalar quantizer implicitly mitigates interference for correlated source transmission over two-way channels.

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

The paper develops a low-complexity full-duplex scheme based on channel-optimized scalar quantization for sending correlated sources over memoryless two-way channels without any error correction. Quantizers are designed to handle user interference implicitly through direct optimization for the channel. Numerical tests transmit Gaussian bivariate sources over binary additive-noise two-way channels that include either additive or multiplicative interference. These tests show the full-duplex scheme reaching higher signal-to-distortion ratios than the corresponding half-duplex scheme. A sympathetic reader would care because the method keeps delay and complexity low while still addressing bidirectional interference.

Core claim

The proposed full-duplex COSQ scheme for lossy transmission of correlated sources over memoryless two-way channels implicitly mitigates TWC interference and, in numerical tests with Gaussian bivariate sources over binary additive-noise TWCs, yields higher signal-to-distortion ratios than the corresponding half-duplex COSQ scheme.

What carries the argument

Channel optimized scalar quantization (COSQ) that tunes scalar quantizers directly to the two-way channel statistics to mitigate interference without explicit coding or joint decoding.

If this is right

  • Full-duplex COSQ achieves higher signal-to-distortion ratio than half-duplex COSQ on the tested channels.
  • The same scalar-quantizer design handles both additive and multiplicative user interference.
  • Low-delay transmission of correlated Gaussian sources is possible without error-correction coding.
  • Implicit interference mitigation works inside a simple scalar quantizer structure.

Where Pith is reading between the lines

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

  • The same design approach might be tested on non-Gaussian sources or on channels with memory to check whether the implicit-mitigation property persists.
  • If the optimization can be made adaptive, the scheme could track slowly varying interference levels in real time.
  • Replacing the scalar quantizer with a vector version could be examined to see whether further gains appear while still avoiding explicit coding.

Load-bearing premise

Optimizing scalar quantizers for the channel can mitigate two-way interference without the observed performance gains depending on the specific optimization routine or the exact channel parameters used in the examples.

What would settle it

A new set of simulations on the same binary additive-noise two-way channels but with different noise variances or source correlations where the full-duplex COSQ no longer exceeds the half-duplex COSQ signal-to-distortion ratio would falsify the central claim.

Figures

Figures reproduced from arXiv: 1907.07269 by Fady Alajaji, Saeed Rezazadeh, Wai-Yip Chan.

Figure 1
Figure 1. Figure 1: The block diagram of the COSQ TWC system. [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: The block diagram of the half-duplex COSQ system where [PITH_FULL_IMAGE:figures/full_fig_p004_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Codebook constellations at terminal two for full-duplex (Fig. 3(a)) and [PITH_FULL_IMAGE:figures/full_fig_p005_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Quantization cells for full-duplex (Fig. 4(a)) and half-duplex [PITH_FULL_IMAGE:figures/full_fig_p006_4.png] view at source ↗
read the original abstract

The problem of lossy transmission of correlated sources over memoryless two-way channels (TWCs) is considered. The objective is to develop a robust low delay and low complexity source-channel coding scheme without using error correction. A simple full-duplex channel optimized scalar quantization (COSQ) scheme that implicitly mitigates TWC interference is designed. Numerical results for sending Gaussian bivariate sources over binary additive-noise TWCs with either additive or multiplicative user interference show that, in terms of signal-to-distortion ratio performance, the proposed full-duplex COSQ scheme compares favourably with half-duplex COSQ.

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

1 major / 1 minor

Summary. The paper addresses lossy transmission of correlated sources over memoryless two-way channels (TWCs). It proposes a full-duplex channel-optimized scalar quantization (COSQ) scheme designed to implicitly mitigate user interference without explicit error correction or joint decoding. For Gaussian bivariate sources sent over binary additive-noise TWCs with either additive or multiplicative interference, numerical comparisons are presented claiming that the full-duplex COSQ achieves higher signal-to-distortion ratio (SDR) than a half-duplex COSQ baseline.

Significance. If the reported numerical advantage holds under reproducible conditions, the work would demonstrate that scalar quantizers can be optimized to handle TWC interference implicitly, yielding a low-delay, low-complexity alternative to schemes that rely on explicit coding. This could be relevant for bidirectional source transmission scenarios where complexity and latency constraints preclude more sophisticated coding.

major comments (1)
  1. [Abstract and numerical results description] The abstract states that numerical results favor full-duplex COSQ, but provides no details on the optimization algorithm, convergence criteria, number of trials, or error bars. This absence directly undermines verification of the central performance claim, as the SDR comparison cannot be assessed for robustness or reproducibility from the given description.
minor comments (1)
  1. The manuscript would benefit from a clear algorithmic description or pseudocode for the COSQ design procedure to allow readers to understand how the quantizers are optimized for the TWC models.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for the detailed review and the opportunity to clarify the presentation of our numerical results. We address the single major comment below.

read point-by-point responses

  1. Referee: [Abstract and numerical results description] The abstract states that numerical results favor full-duplex COSQ, but provides no details on the optimization algorithm, convergence criteria, number of trials, or error bars. This absence directly undermines verification of the central performance claim, as the SDR comparison cannot be assessed for robustness or reproducibility from the given description.

    Authors: We agree that the abstract, owing to length constraints, omits implementation specifics. The body of the manuscript describes the COSQ design, the iterative optimization procedure used to minimize end-to-end distortion, and the simulation setup for the Gaussian bivariate sources over the binary additive-noise TWCs. To improve reproducibility, we will revise the numerical-results section to state the exact optimization algorithm (including the update rule and stopping criterion), the number of random initializations performed, and how the reported SDR values were obtained from those runs. Because the underlying channel is deterministic, conventional error bars are not applicable; we will instead report the range of SDR values observed across initializations to address robustness concerns. These additions will be made without altering the central claims. revision: yes

Circularity Check

0 steps flagged

No significant circularity; empirical numerical comparison only

full rationale

The paper presents a design method for full-duplex COSQ and reports numerical SDR comparisons against half-duplex COSQ on two specific binary TWC models with Gaussian sources. No derivation, theorem, or first-principles prediction is claimed; the result is a direct simulation outcome. No self-citation, fitted-input-as-prediction, or definitional loop is present or load-bearing. The work is self-contained as an empirical engineering design study.

Axiom & Free-Parameter Ledger

0 free parameters · 0 axioms · 0 invented entities

Abstract-only review prevents enumeration of specific free parameters or axioms; the design likely involves fitted quantization thresholds and distortion weights optimized numerically for the given source and channel statistics.

pith-pipeline@v0.9.0 · 5621 in / 1055 out tokens · 17945 ms · 2026-05-24T20:24:06.015276+00:00 · methodology

discussion (0)

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Reference graph

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