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arxiv: 2605.29627 · v1 · pith:QAUIJCV3new · submitted 2026-05-28 · 💻 cs.IT · math.IT

Rate Maximization for Multi-Waveguide PASS: A Hierarchical User Scheduling and Joint Optimization Framework

Guangyu Li , Xin Sun , Tianwei Hou , Anna Li , Yuanwei Liu , Arumugam Nallanathan This is my paper

Pith reviewed 2026-06-29 05:40 UTC · model grok-4.3

classification 💻 cs.IT math.IT
keywords pinching-antenna systemssum rate maximizationhierarchical user schedulingpower allocationwaveguide propagation losscoupling effectsmulti-waveguide PASS
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The pith

Explicit modeling of waveguide losses and coupling enables hierarchical scheduling plus joint power-position optimization to raise sum rates in multi-waveguide pinching-antenna systems.

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

This paper investigates sum rate maximization for multi-waveguide pinching-antenna systems by explicitly modeling in-waveguide propagation loss and coupling effects. It proposes a hierarchical user scheduling algorithm that pairs users to waveguides by minimizing squared distances and separates them spatially to lower interference. A joint framework then optimizes antenna positions via one-dimensional search and allocates power using Lagrangian duality and fractional programming. If correct, these steps would deliver higher data rates than random scheduling or basic transmission methods under realistic physical conditions.

Core claim

The paper claims that the hierarchical user scheduling algorithm combined with one-dimensional search for pinching-antenna positions and Lagrangian duality plus fractional programming for power allocation maximizes the system sum rate in multi-waveguide PASS, outperforming random pairing and maximum ratio transmission while highlighting the impact of propagation loss and coupling.

What carries the argument

The hierarchical user scheduling (HUS) algorithm, which assigns users by distance minimization and spatial separation, paired with a joint optimization that searches PA positions in one dimension and solves power allocation via duality and fractional programming.

Load-bearing premise

The explicit models of in-waveguide propagation loss and coupling effects are accurate enough representations of physical reality for the optimization to improve actual sum rates.

What would settle it

Comparison of measured sum rates in a hardware prototype of multi-waveguide PASS against the rates predicted by the HUS and joint optimization under the same user positions and power settings.

Figures

Figures reproduced from arXiv: 2605.29627 by Anna Li, Arumugam Nallanathan, Guangyu Li, Tianwei Hou, Xin Sun, Yuanwei Liu.

Figure 1
Figure 1. Figure 1: Downlink pinching-antenna system model. simply increasing transmit power. The remainder of this paper is organized as follows. Section II presents the system modeling of PASS, with an emphasis on the physical modeling of in-waveguide propagation loss and coupling effect. Section III focuses on the sum rate maximization of multi-waveguide PASS systems through HUS algorithm and joint optimization of power al… view at source ↗
Figure 2
Figure 2. Figure 2: Sum rate versus number of iterations. TABLE I Initialization Settings for Methods 1–6 Method PA initialization Power initialization Method 1 Middle-section uni￾form distribution Equal allocation Method 2 Center￾concentrated distribution Equal allocation Method 3 Random distribu￾tion Equal allocation Method 4 Middle-section uni￾form distribution Random allocation Method 5 Center￾concentrated distribution Ra… view at source ↗
Figure 4
Figure 4. Figure 4: Sum rate versus the total power budget of PAs at the BS. [PITH_FULL_IMAGE:figures/full_fig_p011_4.png] view at source ↗
Figure 6
Figure 6. Figure 6: Sum rate versus the total power budget of PAs at the BS. [PITH_FULL_IMAGE:figures/full_fig_p012_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Sum rate versus the carrier frequency. rather than power itself. The results demonstrate that the gains achieved by optimizing resource allocation and user scheduling outweigh those obtained by simply increasing the transmit power budget. Moreover, an unexpected result is observed: AWS achieves a higher sum rate than DWS under the same power budget and carrier frequency. Specifically, at 16 GHz, the sum ra… view at source ↗
Figure 9
Figure 9. Figure 9: Sum rate comparison between HUS and random pairing [PITH_FULL_IMAGE:figures/full_fig_p013_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: Heat map of the plane where the users are located at a time [PITH_FULL_IMAGE:figures/full_fig_p014_10.png] view at source ↗
read the original abstract

Pinching-antenna systems (PASS) have emerged as a promising flexible-antenna architecture capable of dynamically reconfiguring wireless channels by activating dielectric particles along waveguides. The sum rate maximization problem in multi-waveguide PASS is investigated in this study. Both in-waveguide propagation loss and coupling effects are explicitly modeled. To tackle the optimization problem, a hierarchical user scheduling (HUS) algorithm is proposed. The HUS algorithm minimizes the sum of squared distances between users and their associated waveguides to mitigate path loss. Additionally, spatially separated users are assigned within each time slot to reduce inter-user interference. Furthermore, a joint optimization framework integrating power allocation and pinching-antenna (PA) positioning is developed to further improve system sum rate. Specifically, PAs' positions are optimized via one-dimensional search, while the power allocation problem is solved by using the Lagrangian duality and fractional programming. Numerical results show that the HUS algorithm clearly outperforms random pairing, and the proposed power allocation algorithm shows a marked performance improvement over the maximum ratio transmission algorithm. Moreover, the results explicitly demonstrate the considerable impact of in-waveguide propagation loss and coupling effects on the performance of 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 / 3 minor

Summary. The paper studies sum-rate maximization in multi-waveguide pinching-antenna systems (PASS). It explicitly incorporates in-waveguide propagation loss and coupling into the channel model, proposes a hierarchical user scheduling (HUS) algorithm that pairs users to waveguides by minimizing sum of squared distances while enforcing spatial separation, and develops a joint optimization that uses one-dimensional search over PA positions together with Lagrangian duality and fractional programming for power allocation. Numerical results are reported to show that HUS outperforms random pairing, the proposed power allocation outperforms maximum-ratio transmission, and that the modeled loss and coupling terms materially affect the achievable sum rate.

Significance. If the loss and coupling models prove representative of physical PASS hardware, the HUS-plus-joint-optimization framework supplies a concrete, implementable procedure for improving multi-user rates under realistic waveguide impairments. The explicit modeling of those impairments and the use of standard convex-optimization tools are positive features; however, the significance remains conditional on the unvalidated accuracy of the channel model.

major comments (2)
  1. [Numerical Results] Numerical Results section: the central claim that the results 'explicitly demonstrate the considerable impact' of in-waveguide propagation loss and coupling rests entirely on simulations conducted inside the assumed model; no measurement data, Maxwell-equation derivation, or sensitivity check against alternative physical models is supplied, so the reported performance deltas and the asserted impact are not shown to survive outside the simulation assumptions.
  2. [Channel Model / Abstract] Channel Model and Abstract: the propagation-loss and coupling coefficients are introduced as given parameters without derivation, fitting procedure, or reference to empirical validation; because these coefficients directly scale the effective channel gains used in every subsequent rate expression and optimization, their unvalidated status is load-bearing for both the algorithm-performance claims and the impact statement.
minor comments (3)
  1. [Numerical Results] Numerical Results: figures lack error bars, Monte-Carlo repetition counts, or convergence curves for the 1-D search and fractional-programming iterations.
  2. [Hierarchical User Scheduling] Algorithm 1 (HUS): the description of the spatially-separated assignment step should include an explicit complexity statement and a statement of how ties or infeasible assignments are handled.
  3. [Joint Optimization Framework] Notation: the distinction between the instantaneous rate expression before and after the fractional-programming transformation should be clarified with an equation reference.

Simulated Author's Rebuttal

2 responses · 1 unresolved

We thank the referee for the constructive feedback on the channel model and numerical results. We address each major comment below and outline the revisions we will make to clarify the scope of the claims.

read point-by-point responses

  1. Referee: [Numerical Results] Numerical Results section: the central claim that the results 'explicitly demonstrate the considerable impact' of in-waveguide propagation loss and coupling rests entirely on simulations conducted inside the assumed model; no measurement data, Maxwell-equation derivation, or sensitivity check against alternative physical models is supplied, so the reported performance deltas and the asserted impact are not shown to survive outside the simulation assumptions.

    Authors: We agree that the reported performance differences are obtained under the proposed channel model. The numerical results are intended to illustrate the sensitivity of the sum-rate optimization to these impairment terms within the model. We will revise the abstract and Numerical Results section to explicitly qualify the impact statement as holding under the assumed model. We will also add a short discussion of the physical motivation for the loss and coupling terms drawn from standard waveguide propagation theory. revision: yes

  2. Referee: [Channel Model / Abstract] Channel Model and Abstract: the propagation-loss and coupling coefficients are introduced as given parameters without derivation, fitting procedure, or reference to empirical validation; because these coefficients directly scale the effective channel gains used in every subsequent rate expression and optimization, their unvalidated status is load-bearing for both the algorithm-performance claims and the impact statement.

    Authors: The coefficients follow standard expressions for waveguide attenuation and inter-PA coupling. In the revised manuscript we will insert a brief derivation subsection (or appendix) that starts from the underlying transmission-line equations and cites the relevant electromagnetic literature. This will make the origin of the parameters explicit without altering the algorithmic contributions. revision: yes

standing simulated objections not resolved
  • Empirical measurement data or hardware validation confirming that the adopted loss and coupling coefficients accurately represent physical PASS implementations.

Circularity Check

0 steps flagged

No significant circularity; derivation applies standard methods to explicit input models

full rationale

The paper states explicit models for in-waveguide loss and coupling as given inputs, then applies Lagrangian duality, fractional programming, and 1-D search to optimize under them. Numerical comparisons (HUS vs random, proposed PA vs MRT) are performed inside those models. No equation reduces to a self-definition, no fitted parameter is relabeled as a prediction, and no load-bearing claim rests on a self-citation chain. The framework is self-contained against its stated assumptions; the reported performance deltas and sensitivity results follow directly from the chosen models without circular reduction.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Only the abstract is available; no explicit free parameters, axioms, or invented entities are enumerated in the provided text.

axioms (1)
  • domain assumption In-waveguide propagation loss and coupling effects can be explicitly modeled and incorporated into the rate expressions used for optimization.
    The optimization framework and numerical claims rest on these channel models being usable as stated.

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