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arxiv: 2605.15129 · v2 · pith:UCP6N54Pnew · submitted 2026-05-14 · 📡 eess.SP

Downlink Performance Analysis of Pinching Antenna Systems: WDMA or NOMA?

Han Zhang , Bingxin Zhang , Yizhe Zhao , Kun Yang This is my paper

Pith reviewed 2026-05-20 20:28 UTC · model grok-4.3

classification 📡 eess.SP
keywords pinching antenna systemsWDMANOMAoutage probabilityachievable ratespectral efficiencyantenna placementchannel model
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The pith

In pinching antenna systems NOMA reaches higher spectral efficiency at high SNR while WDMA stays more reliable at low to moderate SNR.

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

The paper develops an analytical framework to compare waveguide division multiple access and non-orthogonal multiple access in downlink pinching antenna systems. It introduces a unified channel model that incorporates antenna placement, user positions, and distance-based signal loss, then derives closed-form and integral expressions for outage probability and average achievable rate. Monte Carlo checks confirm the expressions. The comparison shows NOMA exploits successive interference cancellation to improve efficiency when transmit power is large, whereas WDMA avoids certain interference problems when power is limited yet hits an outage floor and rate limit as power grows. The work supplies concrete guidance on choosing the access method and siting the antennas.

Core claim

This paper presents an analytical framework for downlink pinching antenna systems employing waveguide division multiple access and non-orthogonal multiple access. A unified channel model captures antenna deployment, user spatial distribution, and path loss. Closed-form and single-integral expressions for outage probability and average achievable rate are derived and validated via Monte Carlo simulations. The results establish that NOMA achieves higher spectral efficiency at high transmit SNR due to successive interference cancellation, whereas WDMA offers more reliable performance at low to moderate SNR but suffers from an outage floor and rate saturation at high SNR, and that WDMA is more敏感

What carries the argument

The unified channel model that incorporates antenna deployment, user spatial distribution, and path loss to produce closed-form and integral expressions for outage probability and achievable rate under both WDMA and NOMA.

If this is right

  • NOMA should be selected when the system operates at high transmit SNR to obtain better spectral efficiency.
  • WDMA should be preferred at low to moderate SNR to avoid outage floors and maintain reliable links.
  • Antenna placement decisions must account more carefully for user spatial distribution under WDMA because of inter-waveguide interference.
  • Performance comparisons between the two schemes can be used directly to decide which access method to deploy for given SNR regimes.

Where Pith is reading between the lines

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

  • A hybrid scheduler that switches between WDMA and NOMA according to instantaneous SNR could combine the reliability of one with the efficiency of the other.
  • The sensitivity of WDMA to user locations suggests that adaptive pinching of waveguide elements might reduce inter-waveguide interference more effectively than fixed placement.
  • The same modeling approach could be extended to multi-cell or uplink scenarios to test whether the SNR-dependent preference between the schemes persists.

Load-bearing premise

The unified channel model is accurate enough to support the closed-form and integral derivations for outage probability and achievable rate in real deployments.

What would settle it

Real-world measurements or ray-tracing simulations of a pinching antenna array in which WDMA shows no rate saturation at high transmit power would falsify the model's prediction of an outage floor.

Figures

Figures reproduced from arXiv: 2605.15129 by Bingxin Zhang, Han Zhang, Kun Yang, Yizhe Zhao.

Figure 1
Figure 1. Figure 1: System model of PASS. A. WDMA We consider a downlink PASS with WDMA, as shown in [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Performance versus transmit SNR for different PA heights. [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Performance comparison of NOMA and WDMA under two spatial [PITH_FULL_IMAGE:figures/full_fig_p007_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Performance comparison of WDMA and NOMA under different [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
read the original abstract

This paper presents an analytical framework for downlink pinching antenna systems (PASS) employing waveguide division multiple access (WDMA) and non-orthogonal multiple access (NOMA). A unified channel model is developed to capture antenna deployment, user spatial distribution, and path loss. Closed-form and single-integral expressions for the outage probability and average achievable rate are derived and validated via Monte Carlo simulations. The results show that NOMA achieves higher spectral efficiency at high transmit signal-to-noise ratio (SNR) due to successive interference cancellation (SIC), whereas WDMA offers more reliable performance at low to moderate SNR but suffers from an outage floor and rate saturation at high SNR. Moreover, WDMA performance is more sensitive to the user spatial distribution due to the spatially dependent inter-waveguide interference. These findings provide design insights for access-scheme selection and antenna placement in PASS.

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. This paper presents an analytical framework for downlink pinching antenna systems (PASS) employing waveguide division multiple access (WDMA) and non-orthogonal multiple access (NOMA). A unified channel model is developed to capture antenna deployment, user spatial distribution, and path loss. Closed-form and single-integral expressions for the outage probability and average achievable rate are derived and validated via Monte Carlo simulations. The results show that NOMA achieves higher spectral efficiency at high transmit signal-to-noise ratio (SNR) due to successive interference cancellation (SIC), whereas WDMA offers more reliable performance at low to moderate SNR but suffers from an outage floor and rate saturation at high SNR. Moreover, WDMA performance is more sensitive to the user spatial distribution due to the spatially dependent inter-waveguide interference. These findings provide design insights for access-scheme selection and antenna placement in PASS.

Significance. If the unified channel model accurately represents PASS propagation, the closed-form and single-integral expressions would provide a useful analytical tool for evaluating outage and rate performance without relying solely on simulations. The explicit comparison of NOMA and WDMA across SNR regimes, together with the Monte Carlo validation, supplies concrete design guidance on access-scheme selection and antenna placement for this emerging technology. The internal consistency checks are a positive feature of the work.

major comments (2)
  1. [System Model] System Model section: The unified channel model is load-bearing for every subsequent expression. The formulation of spatially dependent inter-waveguide interference for WDMA is presented without explicit electromagnetic justification or comparison to existing pinching-antenna propagation models; any inaccuracy here directly affects the predicted outage floor and the claim that WDMA is more sensitive to user spatial distribution.
  2. [Performance Analysis] Performance Analysis section: The closed-form outage probability and achievable-rate expressions for both schemes rest on the channel model and standard assumptions (e.g., perfect SIC for NOMA at high SNR). The manuscript should clarify whether residual interference or imperfect cancellation is accounted for, because the headline conclusion that NOMA yields higher spectral efficiency at high SNR depends on this modeling choice.
minor comments (2)
  1. Notation for path-loss exponents and waveguide parameters should be defined immediately before their first use in the equations to improve readability.
  2. Figure captions could explicitly state the number of users, waveguide length, and SNR range used in the Monte Carlo runs for easier cross-reference with the analytical curves.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the constructive and detailed comments on our manuscript. We have carefully addressed each major point below and revised the manuscript to enhance clarity and rigor where appropriate.

read point-by-point responses

  1. Referee: [System Model] System Model section: The unified channel model is load-bearing for every subsequent expression. The formulation of spatially dependent inter-waveguide interference for WDMA is presented without explicit electromagnetic justification or comparison to existing pinching-antenna propagation models; any inaccuracy here directly affects the predicted outage floor and the claim that WDMA is more sensitive to user spatial distribution.

    Authors: We appreciate the referee's emphasis on the foundational role of the channel model. The unified model integrates waveguide mode propagation with pinching-antenna radiation and incorporates user spatial distribution via a geometry-based path-loss formulation; the spatially dependent inter-waveguide interference term follows directly from the relative positions of the waveguides and users. While the model builds on standard assumptions in the PASS literature, we agree that additional electromagnetic justification and explicit comparisons would strengthen the presentation. In the revised manuscript we will add a dedicated paragraph in the System Model section deriving the interference coefficient from the Friis transmission formula adapted to waveguide-fed radiators and contrasting it with prior pinching-antenna models. This revision will be marked as an addition to the text. revision: yes

  2. Referee: [Performance Analysis] Performance Analysis section: The closed-form outage probability and achievable-rate expressions for both schemes rest on the channel model and standard assumptions (e.g., perfect SIC for NOMA at high SNR). The manuscript should clarify whether residual interference or imperfect cancellation is accounted for, because the headline conclusion that NOMA yields higher spectral efficiency at high SNR depends on this modeling choice.

    Authors: We agree that the modeling assumptions must be stated unambiguously. Our NOMA analysis employs the standard perfect successive interference cancellation (SIC) assumption, which is valid in the high-SNR regime where the interference term vanishes after cancellation; residual interference from imperfect SIC is not incorporated in the closed-form expressions. Consequently, the reported spectral-efficiency advantage of NOMA at high SNR holds under this ideal-SIC premise. In the revised Performance Analysis section we will explicitly declare the perfect-SIC assumption, note its implications for the high-SNR conclusion, and briefly discuss the potential impact of imperfect cancellation as a direction for future refinement. revision: yes

Circularity Check

0 steps flagged

Derivation of outage and rate expressions is self-contained

full rationale

The paper develops a unified channel model from standard wireless propagation principles to capture antenna deployment, user spatial distribution, and path loss, then applies conventional stochastic geometry and information-theoretic techniques to obtain closed-form and single-integral expressions for outage probability and achievable rate. Monte Carlo simulations are used solely to verify internal consistency between the derived expressions and numerical results. The SNR-regime comparisons between NOMA (via SIC) and WDMA (with outage floor) follow directly from these expressions without any fitted parameters renamed as predictions, self-definitional loops, or load-bearing self-citations that reduce the central claims to their own inputs by construction.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Abstract-only review provides no explicit list of fitted parameters or invented entities; the central derivations rest on the stated unified channel model.

axioms (1)
  • domain assumption A unified channel model accurately captures antenna deployment, user spatial distribution, and path loss for the pinching antenna system.
    This model is the foundation for all subsequent outage and rate derivations.

pith-pipeline@v0.9.0 · 5677 in / 1242 out tokens · 88561 ms · 2026-05-20T20:28:11.301360+00:00 · methodology

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Reference graph

Works this paper leans on

11 extracted references · 11 canonical work pages

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