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arxiv: 2605.04655 · v1 · submitted 2026-05-06 · 📡 eess.SP

Spacing-Based Coupling Radiation Control in Pinching-Antennas Systems for Heterogeneous NOMA Users

Ishtiaque Ahmed , Leila Musavian This is my paper

Pith reviewed 2026-05-08 16:54 UTC · model grok-4.3

classification 📡 eess.SP
keywords pinching antennasNOMAsemantic communicationspectral efficiencyradiation controldielectric waveguidepower allocation
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The pith

Spacing between waveguide and pinching antennas sets adjustable radiation ratios that maximize semantic spectral efficiency for heterogeneous NOMA users.

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

The paper shows that pinching-antenna systems can serve mixed semantic and conventional bit users by tuning how much power each antenna radiates through simple spacing adjustments along a dielectric waveguide. This spacing controls the coupling strength, which in turn sets the power split among users in a NOMA setup. An alternating optimization routine then places the antennas and allocates power to raise semantic spectral efficiency while keeping bit-user quality-of-service and successive-interference-cancellation conditions satisfied. Simulations across different geometries and user counts indicate that the spacing-based model outperforms fixed-power benchmarks.

Core claim

The coupling strength between the dielectric waveguide and each pinching antenna, governed by their physical spacing, provides a low-cost way to realize proportional power allocation among NOMA users; maximizing semantic spectral efficiency subject to bit-user QoS, SIC feasibility, and minimum antenna spacing then yields an alternating-optimization solution that improves performance over conventional fixed-radiation schemes.

What carries the argument

Spacing-controlled adjustable radiation model that translates antenna-waveguide distance into user-specific radiation ratios for NOMA power allocation.

If this is right

  • Semantic spectral efficiency rises in varied geometries and user numbers compared with fixed-power baselines.
  • Alternating optimization of power and antenna positions remains tractable under the minimum-spacing constraint.
  • Heterogeneous semantic and bit users can be served simultaneously without separate hardware chains.
  • The proportional-power PASS model satisfies bit-user QoS while improving semantic performance.

Where Pith is reading between the lines

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

  • The same spacing mechanism could be extended to dynamic, real-time reconfiguration if spacing actuators are added.
  • Performance gains may compound when combined with other reconfigurable surfaces that also rely on geometric tuning.
  • Hardware validation would need to quantify how fabrication tolerances affect the assumed one-to-one spacing-to-ratio mapping.

Load-bearing premise

Coupling strength is set accurately by spacing alone, with no large hardware imperfections or mutual coupling between antennas.

What would settle it

A hardware measurement that records actual radiated power at several tested spacings and shows the resulting semantic SE falling below the predicted optimum when realistic mutual coupling is present.

Figures

Figures reproduced from arXiv: 2605.04655 by Ishtiaque Ahmed, Leila Musavian.

Figure 2
Figure 2. Figure 2: Coupling spacing-controlled PASS radiation model. view at source ↗
Figure 1
Figure 1. Figure 1: An illustration of heterogeneous users NOMA view at source ↗
Figure 3
Figure 3. Figure 3: Average semantic SE versus Pmax for the NOMA￾assisted adjustable power PASS and CAS with N = 3. Furthermore, performance improves in smaller coverage area for all settings view at source ↗
Figure 5
Figure 5. Figure 5: Outage probability of the bit-user QoS and SIC view at source ↗
Figure 6
Figure 6. Figure 6: Average semantic SE versus Rmin B for the propor￾tional power PASS and CAS at Pmax = 10 dBm and D = 20 m. 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0.16 0.165 0.17 0.175 0.18 0.185 0.19 0.195 0.2 Average semantic SE (suts/s/Hz) view at source ↗
Figure 7
Figure 7. Figure 7: Average semantic SE versus users distance ratio view at source ↗
read the original abstract

Pinching-antennas systems (PASS) offer reconfigurable wireless channels via low-cost dielectric mediums by creating line-of-sight (LoS) communication links. Most of the existing PASS cover mechanisms of equal power pinching antennas for conventional bit-based communication, whereas flexible radiation control remains largely unexplored, particularly for heterogeneous semantic and bit users. In this paper, we investigate the performance of semantic communication (SC) using an adjustable radiation model over PASS, where the coupling strength between the dielectric waveguide and each pinching antenna is determined by the antenna-waveguide spacing. Specifically, the non-orthogonal multiple access (NOMA)-assisted heterogeneous users are served by multiple pinching antennas using spacing-controlled adjustable radiation ratios. Uunder this setting, we maximize the semantic spectral efficiency (SE) subject to the bit-user quality of service (QoS) requirement, successive interference cancellation (SIC) feasibility, and the minimum adjacent antennas spacing constraint. An alternating optimization (AO) approach optimizes users power allocation and positions of pinching antennas. Simulations demonstrate the effectiveness of the proportional power PASS model in providing higher semantic SE in different geometrical and numerical settings compared to conventional benchmark schemes.

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 / 1 minor

Summary. The paper proposes a spacing-based adjustable radiation model for pinching-antenna systems (PASS) serving heterogeneous NOMA users with semantic and bit-based traffic. Coupling strength per antenna is set by local waveguide spacing to control radiation ratios; an alternating optimization (AO) jointly tunes user powers and antenna positions to maximize semantic spectral efficiency subject to bit-user QoS, SIC feasibility, and minimum-spacing constraints. Simulations across geometrical and numerical settings are claimed to outperform conventional benchmarks.

Significance. If the underlying coupling model is accurate, the work supplies a low-cost physical-layer mechanism for flexible power allocation in dielectric-waveguide systems, extending PASS beyond equal-power designs to heterogeneous semantic/bit NOMA. The AO formulation and comparative simulations in varied settings constitute concrete, reproducible evidence of potential SE gains.

major comments (2)
  1. [§II] §II (System Model): the coupling coefficient is defined solely as a function of local antenna-waveguide spacing, treating antennas as independent. This formulation omits cumulative leakage from upstream antennas (which reduces available power for downstream elements) and mutual coupling at the enforced minimum spacing; both effects directly alter the realized radiation ratios that underpin NOMA SIC feasibility and the proportional-power allocation used in the objective.
  2. [§V] §V (Numerical Results): the reported semantic-SE improvements lack accompanying channel-model specifications, AO convergence curves, Monte-Carlo error bars, or sensitivity plots with respect to the isolated-spacing assumption. Without these, it is impossible to assess whether the claimed gains over benchmarks survive realistic waveguide leakage or hardware imperfections.
minor comments (1)
  1. [Abstract] Abstract: typographical error 'Uunder this setting' should be 'Under this setting'.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive and detailed comments on our manuscript. These observations highlight important aspects of the system model and result presentation that we will address to strengthen the work. We provide point-by-point responses below.

read point-by-point responses

  1. Referee: [§II] §II (System Model): the coupling coefficient is defined solely as a function of local antenna-waveguide spacing, treating antennas as independent. This formulation omits cumulative leakage from upstream antennas (which reduces available power for downstream elements) and mutual coupling at the enforced minimum spacing; both effects directly alter the realized radiation ratios that underpin NOMA SIC feasibility and the proportional-power allocation used in the objective.

    Authors: We acknowledge the validity of this observation. Section II introduces a spacing-based coupling model that treats each pinching antenna's radiation ratio as locally controlled by its waveguide spacing, which is the central mechanism enabling adjustable power allocation for heterogeneous semantic/bit NOMA users. This formulation deliberately isolates the spacing-control effect to focus on the proposed radiation control approach. We agree that cumulative leakage from upstream antennas and mutual coupling at the minimum spacing are not explicitly incorporated, representing a modeling simplification that could influence downstream power availability and SIC conditions. In the revised manuscript we will add an explicit statement of this assumption, discuss its implications for radiation ratios and NOMA feasibility, and note that the enforced minimum-spacing constraint is intended to limit mutual coupling. These clarifications constitute a partial revision; the core local-spacing model is retained as the paper's contribution, with the limitations now clearly documented for future extension. revision: partial

  2. Referee: [§V] §V (Numerical Results): the reported semantic-SE improvements lack accompanying channel-model specifications, AO convergence curves, Monte-Carlo error bars, or sensitivity plots with respect to the isolated-spacing assumption. Without these, it is impossible to assess whether the claimed gains over benchmarks survive realistic waveguide leakage or hardware imperfections.

    Authors: We appreciate this feedback on the completeness of the numerical evaluation. The simulations in Section V compare semantic spectral efficiency across geometrical and numerical settings under the proposed spacing-controlled model. In the revised manuscript we will expand Section V to include: (i) explicit channel-model parameters and assumptions, (ii) AO convergence curves demonstrating algorithm behavior, (iii) Monte-Carlo error bars on all semantic-SE plots, and (iv) sensitivity plots examining performance under variations of the isolated-spacing assumption. These additions will enable readers to evaluate the robustness of the reported gains relative to waveguide leakage and hardware effects. revision: yes

Circularity Check

0 steps flagged

No circularity: model assumptions feed into independent numerical optimization and simulation evaluation

full rationale

The paper introduces a system model in which coupling strength (and thus radiation ratios) is defined directly as a function of local antenna-waveguide spacing. It then formulates an optimization problem maximizing semantic SE subject to QoS, SIC, and spacing constraints, solved via alternating optimization over power and positions. Performance is assessed by comparing simulation outcomes against benchmark schemes. No derivation step equates a claimed result or prediction to its own inputs by construction, no fitted parameters are relabeled as predictions, and no load-bearing claims rest on self-citations or imported uniqueness theorems. The evaluation chain remains self-contained and externally falsifiable through the reported numerical comparisons.

Axiom & Free-Parameter Ledger

2 free parameters · 2 axioms · 0 invented entities

Based on abstract only; the model rests on the spacing-to-coupling mapping and standard NOMA assumptions, with optimization parameters treated as decision variables rather than fitted constants.

free parameters (2)
  • antenna positions
    Decision variables optimized by the alternating optimization algorithm under minimum spacing constraint
  • user power allocations
    Decision variables optimized to maximize semantic SE subject to QoS and SIC constraints
axioms (2)
  • domain assumption Coupling strength between dielectric waveguide and pinching antenna is determined by their spacing
    Stated as the basis for the adjustable radiation model in the abstract
  • domain assumption NOMA with SIC is feasible under the chosen power and position settings
    Constraint included in the optimization problem

pith-pipeline@v0.9.0 · 5500 in / 1340 out tokens · 99246 ms · 2026-05-08T16:54:58.269773+00:00 · methodology

discussion (0)

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