Pinching-Antenna Systems with LoS Blockages

Chongjun Ouyang; Kaidi Wang; Yuanwei Liu; Zhiguo Ding

REVIEW 4 major objections 5 minor 2 cited by

Pinching-Antenna Systems with LoS Blockages

T0 review · 4 major / 5 minor · reviewed 2026-08-06 · deepseek-v4-flash

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Pith's one-line read This paper claims that selectively activating pre-installed pinching antennas can turn LoS blockages into a tool for interference suppression, and that a matching-based algorithm jointly assigning waveguides and antennas significantly…

desk verdict Useful incremental paper on pinching antennas with blockages; Solution 1 is solid, but Solution 2's LoS/distance proxy is sold as a theorem when it is a heuristic. read the letter →

arxiv 2507.10173 v1 pith:JZGWXN5D submitted 2025-07-14 eess.SP

Kaidi Wang , Chongjun Ouyang , Yuanwei Liu , Zhiguo Ding This is my paper

classification eess.SP

keywords pinchingantennasline-of-sightblockageswaveguideassignmentantennaactivationmatchingtheorysum-ratemaximizationinterferencesuppressionnear-fieldcommunications

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

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

The reading

The paper studies a downlink where parallel waveguides, each carrying a set of pre-installed pinching antennas, serve an equal number of users in a room full of fixed obstacles. Its central claim is that deliberately choosing which antenna on which waveguide is active lets the system open line-of-sight paths to the desired user while leaving non-line-of-sight paths to other users, so the same blockages that hurt fixed antennas become a way to suppress interference. To make this choice, the paper formulates a sum-rate maximization problem over waveguide assignment and antenna activation, and solves it with a matching-based algorithm. The important practical message is that a low-complexity preference based only on LoS indicators and distances can approach the full sum-rate-based solution when scatterers are weak, at a fraction of the computational cost. If this holds, indoor millimeter-wave deployments could get large throughput gains from a modest amount of antenna-selection computation.

What carries the argument

The machinery is a three-sided one-to-one matching among users, waveguides, and pinching antennas, with swap-blocking pairs as the local improvement rule. A swap matching exchanges the waveguides of two users and, for each involved waveguide, re-evaluates all M antennas to decide whether to switch activation; a swap is accepted only if it strictly increases the total sum rate. The paper offers two preference designs: a sum-rate-based preference (Solution 1) and a LoS-and-distance proxy (Solution 2) that uses three inequalities, covering whether the new antenna creates a LoS link for the desired user, whether the user is closer to it, and whether the number of LoS interference links decreases, with at least one inequality strict and the others weak. The same proxy structure guides waveguide swaps, and the algorithm terminates when no swap-blocking pair survives a full cycle, which the paper equates with stability of the resulting matching.

What would settle it

Place strong scatterers so that the proxy-preferred antenna sits in a deep NLoS null for the served user while the original antenna has a strong NLoS component; if a swap satisfying conditions (14) or (16) reduces the true sum rate, the proxy's sufficiency claim fails. A direct exhaustive comparison over all matchings in a small 4-user, 4-waveguide grid would settle the issue.

Watch

Extended reading notes

Core claim

In an obstructed indoor downlink with K parallel waveguides, N = K single-antenna users, and M pre-installed pinching antennas per waveguide, the paper claims that LoS blockages are not merely obstacles but exploitable resources. By assigning each user to a unique waveguide and activating exactly one antenna per waveguide, the system can deliberately establish LoS links for desired signals while keeping NLoS links for interference, and a matching-based algorithm that repeatedly performs swap-blocking operations converges to a stable matching. The paper further claims that a simplified preference based only on LoS indicators and distances, rather than full sum-rate computation, approaches the sum-rate-based solution when scatterers are absent and still improves throughput when they are present, while reducing the number of computations to 1/[N(K+1)] of the rate-based approach. Simulation results in the paper show that both proposed solutions outperform fixed-location antennas, and the advantage grows as the blockage radius increases.

Load-bearing premise

The load-bearing premise is that a switch to an antenna that is closer, with more LoS links for the desired user and fewer LoS links to others, always raises the total rate; the paper asserts this without proof and it ignores the strength of scattered NLoS paths.

Editorial extensions

If this is right

Pinching-antenna systems with selective activation can outperform fixed-location antennas in obstructed environments even before any optimization, as the initial-state results show.
Larger blockage radii improve the achievable sum rate of the proposed solutions while degrading the fixed-antenna benchmark, so the benefit of pinching antennas widens as obstructions become more severe.
The LoS-and-distance proxy (Solution 2) runs at 1/[N(K+1)] the computations of the sum-rate-based preference and approaches its performance when scatterers are absent, offering a practical complexity-performance trade-off.
With many scatterers, Solution 2 still beats fixed antennas and the unoptimized initial state, but its gap to Solution 1 grows because the proxy ignores NLoS link quality.
The matching-based algorithm converges to a stable matching where no user and waveguide pair has an incentive to swap, providing a principled stopping point for the joint assignment and activation problem.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

The sufficiency claim behind Solution 2 is the most delicate part: if a swap that improves the LoS-and-distance proxy ever lowers the true sum rate, one could repair the proxy by adding rough NLoS-path gain estimates to the three inequalities, keeping most of the complexity savings.
The same matching formulation transfers to other discrete-position flexible antennas, such as movable or fluid antennas with quantized positions, because it only relies on a finite set of candidate channel states.
Because the algorithm only accepts swaps that raise sum rate, it monotonically improves from any starting matching, so it could plausibly track slowly moving users by re-running over time; the paper does not test dynamic scenarios.
The result that blockages suppress interference suggests that deliberate placement of absorbing or reflective blockers could be co-designed with antenna activation, although the paper treats blockages as fixed environmental features.

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Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

Colleague — quick take on arXiv:2507.10173.

The paper does something genuinely useful: it extends the pinching-antenna line to multi-waveguide setups with LoS blockages and formulates the joint waveguide-assignment/antenna-activation problem. The matching-based algorithm for Solution 1 (sum-rate preference) is a reasonable local search: each swap is accepted only if it strictly raises sum rate, so it converges to a stable matching. That part is fine.

The real contribution is the second preference design, using LoS indicators and distances to avoid computing rates. The claim in Sec. III-C is that conditions (14) and (16) are sufficient for a strict sum-rate increase. That is not proven, and it is false when NLoS components are present. The channel is h = phi h_LoS + h_NLoS, and the sum rate depends on the magnitude of the whole channel. A switch can satisfy (14a–c) — new LoS path, shorter distance, fewer LoS interference links — while the old antenna had a strong NLoS path through a nearby scatterer and the new one doesn't. The desired-signal loss can outweigh the LoS gains. The paper later concedes Solution 2 underperforms with scatterers, but it never retreats from the sufficiency claim. That matters because convergence and stability of Solution 2 rely on monotone sum-rate improvement; if the proxy can accept a sum-rate-decreasing swap, the algorithm's termination is not guaranteed.

Simulation methodology is thin: no error bars, no seed or placement details for scatterers and blockages beyond a figure, no comparison across random initializations. That said, the qualitative trend — pinching antennas exploiting blockages to suppress interference — is plausible and matches the intuition from the authors' earlier work.

Who is this for? People working on flexible antennas and matching-based resource allocation. It is a letter, so the depth is limited, but the core question — whether cheap proxies can capture most of the gain — is worth asking, and the paper gives a starting point even if the answer is not rigorous.

My recommendation: read it if you care about pinching antennas, but treat Solution 2 as a heuristic. If you referee it, ask the authors to either prove (14) under mild conditions or reframe it as an approximate preference and bound the performance loss. A serious referee should engage with it; I would not desk-reject.

Referee Report

4 major / 5 minor

Summary. This letter studies a downlink multi-waveguide pinching-antenna system with LoS blockages. With N=K users and waveguides, each waveguide activates one of M pre-installed pinching antennas, and the problem is to assign users to waveguides and to activate antennas so as to maximize the sum rate. The authors formulate an integer program and solve it approximately with a swap-based matching algorithm. Two preference designs are used: Solution 1 compares the true sum rates, while Solution 2 uses conditions on LoS indicators and distances to reduce computation. Simulations compare both solutions with fixed-location antennas and with a random initial state under varying transmit power, blockage radius, and number of scatterers. The paper claims that the proposed system and algorithms significantly improve throughput and that LoS blockages can be exploited for interference suppression.

Significance. If the claims are substantiated, the letter makes a useful practical contribution: it introduces a matching-theoretic local search for pinching-antenna activation and waveguide assignment under blockages, and the LoS/distance proxy (Solution 2) could offer a low-complexity alternative. The paper uses appropriate external baselines (fixed-location antennas and a random initial state), and it explicitly acknowledges in Section IV that Solution 2 underperforms Solution 1 when scatterers are present. However, the theoretical support for Solution 2 is currently missing, and the simulation evidence lacks error characterization. The central idea is plausible, but the manuscript needs to either prove or explicitly recharacterize the sufficiency conditions as heuristics before the complexity-performance trade-off claim is acceptable.

major comments (4)

[III-C] Section III-C, Eq. (14): The assertion that conditions (14a)-(14c), being non-strict with at least one strict inequality, imply the strict preference in (11) is not proved and is not implied by the channel model. Since h_{k,m,n} = phi_{k,m,n} h^LoS_{k,m,n} + h^NLoS_{k,m,n} in Eq. (3), the desired and interference powers in Eq. (7) depend on the NLoS magnitudes, not only on LoS indicators and distances. A switch satisfying (14a), (14b), and (14c) can lose a strong NLoS desired path and reduce the true sum rate. The paper itself states in Section IV that Solution 2 underperforms when scatterers are present, but this concession does not repair the unsupported sufficiency claim. Please either provide a rigorous derivation under explicit assumptions or label (14) as a heuristic and adjust the claims about Solution 2's performance.
[III-C] Section III-C, Eq. (16): The same issue arises for the waveguide-swap conditions. A swap changes the desired and interference channels of both involved users and can trigger antenna re-activation on the affected waveguides; conditions (16a)-(16c) track only LoS indicators and distances, so they do not bound the true sum-rate change in Eq. (7). A swap satisfying all three conditions can decrease the sum rate when NLoS terms dominate. Consequently, the stability statement in Section III-D is only valid with respect to the proxy preference, not with respect to the sum-rate preference in Eq. (10). Please add a proof of the claimed implication or explicitly characterize the resulting matching as stable for the proxy preference only.
[III-D] Section III-D: The convergence argument is sound in that each accepted swap strictly improves the relevant preference and the state space is finite, but the letter overstates what follows. For Solution 1, the terminal matching is a local optimum of the swap neighborhood, not a global optimum, and no optimality gap is given. For Solution 2, even the local-optimality statement is relative to the proxy preference once the issues in (14)/(16) are addressed. The sentence 'the resulting matching is, by Definition 3, always stable' should be qualified accordingly. In addition, the claimed complexity reduction to 1/(N(K+1)) of the original computational load should be derived from an explicit count of elementary operations.
[IV] Section IV, Figs. 3-5: The simulation curves appear to be generated from a single scatterer realization and a single random initial matching, with no error bars or averaging. Because the algorithm's outcome depends on the random initialization and the scatterer positions are random, the claim of 'significantly improving system throughput' needs either confidence intervals or averages over many independent trials, particularly for the L=3 case where Solution 2 is visibly below Solution 1.

minor comments (5)

[III-A] Definition 1: The notation Psi: N -> K -> M is ambiguous; a standard function from N to K to M would return an element of M, whereas later lines treat Psi(k) as a pair (n,m). Please define the mapping more carefully.
[IV] The caption of Fig. 2 states that the proposed algorithm improves fairness, but no fairness metric is defined in the letter; either define the metric or remove the claim.
[III-C] The sentence 'This condition typically satisfied under the following scenarios' contains a grammatical error and, more importantly, the informal wording should be replaced by a precise statement of the claim, especially because the conditions are the basis of the proxy preference.
[III-C] In Eq. (16b), the distance-change notation for the second user, such as Delta D^{n'}_{k',m'->k,m}, is used implicitly without a definition analogous to Eq. (15); please define it explicitly.
[II-B] The equal power allocation P_t/K across waveguides is fixed in Eq. (5); this should be stated explicitly as an assumption in the problem formulation, since it restricts the optimum.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the central throughput claim is benchmarked against external baselines, and the LoS/distance proxy is an explicit suboptimal heuristic rather than a fitted input relabeled as a prediction.

full rationale

The paper's performance claims are validated by direct simulation against conventional fixed-location antennas and a random initial matching state (Figs. 3-5), using the stated channel model (1)-(4) and sum-rate objective (7)-(8). No parameter is fitted to those simulation curves, and no result is predicted from data used to fit it. The self-citations ([4], [9]) motivate the system model and are not used to prove the numerical gains, which are computed from the paper's own equations. The Section III-C assertion that conditions (14a)-(14c) imply the strict sum-rate preference (11) is unsupported and may be false when NLoS paths dominate; however, this is a correctness and complexity-tradeoff gap, not a circular reduction, because the proxy conditions are not defined in terms of the sum rate and the paper explicitly concedes in Sec. IV that Solution 2 underperforms when scatterers are present. No derivation step reduces to its own input by construction.

Assumptions & free parameters 0 free parameters · 5 assumptions · 0 invented entities

The central algorithm depends on standard channel-model assumptions and on an unproved sufficiency claim for the LoS-distance preference proxy. No free parameters are fitted to data; system parameters (M=20, d=3m, fc=28GHz, sigma2=-80dBm) are fixed simulation inputs, not fudge factors. No new physical entities are invented.

assumptions (5)

domain assumption Spherical-wave LoS and scatterer-based NLoS channel model (Eqs 1-3) fully captures propagation.
Sec II-A; no experimental or ray-tracing validation is provided.
domain assumption LoS existence between an antenna and a user is a known binary quantity determined only by blockage geometry.
Eq (3) and conditions (14)/(16) treat phi as available and static; in practice phi must be estimated or measured.
domain assumption Dielectric waveguide propagation loss is negligible.
Sec II-B after Eq (5), justified only by citation [11].
ad hoc to paper Sufficiency of conditions (14)/(16) for the sum-rate preferences (11)/(10).
Sec III-C; asserted without proof, and ignores NLoS link quality.
standard math The three-sided matching game has a stable core as in [12].
Sec III-A/B invokes [12] to guarantee convergence to a stable matching; no proof that this specific utility satisfies the required conditions.

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Cite this review

Pith. "Pith review of Pinching-Antenna Systems with LoS Blockages." pith.science (2026). https://pith.science/paper/JZGWXN5D

@misc{pith2026250710173,
  author       = {Pith},
  title        = {Pith review of: Pinching-Antenna Systems with LoS Blockages},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/JZGWXN5D}},
  note         = {Machine review of arXiv:2507.10173}
}

read the original abstract

The aim of this letter is to explore the capability of pinching-antenna systems to construct line-of-sight (LoS) links in the presence of LoS blockages. Specifically, pinching antennas are pre-installed at preconfigured positions along waveguides and can be selectively activated to create LoS links for enhancing desired signals and non-line-of-sight (NLoS) links for eliminating inter-user interference. On this basis, a sum-rate maximization problem is formulated by jointly optimizing waveguide assignment and antenna activation. To solve this problem, a matching based algorithm is proposed using two distinct preference designs. Simulation results demonstrate that the considered pinching-antenna system and proposed solutions can dynamically establish LoS links and effectively exploit LoS blockages to mitigate interference, thereby significantly improving system throughput.

Figures

Figures reproduced from arXiv: 2507.10173 by the authors.

**Figure 2.** An illustration of the proposed solution, where [PITH_FULL_IMAGE:figures/full_fig_p011_2.png] view at source ↗

**Figure 3.** Impact of the transmit power on the sum rate, where [PITH_FULL_IMAGE:figures/full_fig_p011_3.png] view at source ↗

Figures from the paper (2 more)

**Figure 4.** Figure 4: Impact of the radius of blockage on the sum rate, where [PITH_FULL_IMAGE:figures/full_fig_p012_4.png]

**Figure 5.** Figure 5: Impact of the number of scatterers on the sum rate, whe [PITH_FULL_IMAGE:figures/full_fig_p012_5.png]

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Forward citations

Cited by 2 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

Pinching-Antenna System Design with LoS Blockage: Does In-Waveguide Attenuation Matter?
eess.SP 2025-08 conditional novelty 5.0 of 10

Under realistic LoS blockage, ignoring in-waveguide attenuation costs only about α^2/(β ln2) bps/Hz in large dense-blockage areas, but the loss grows with area squared when blockages are sparse.
Multi-Mode Pinching-Antenna Systems: Mode Selection or Mode Combining?
eess.SP 2026-03 conditional novelty 4.0 of 10

Multi-mode pinching-antenna systems using mode combining or mode selection can outperform single-mode PASS and hybrid beamforming in sum rate.

Reference graph

Works this paper leans on

12 extracted references · 7 canonical work pages · cited by 2 Pith papers

[1]

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Pith tools

Reviewed August 6, 2026 · model on record in the stance chip above.

[1] [1]

Fl uid antenna systems,

K.-K. Wong, A. Shojaeifard, K.-F. Tong, and Y . Zhang, “Fl uid antenna systems,” IEEE Trans. Wireless Commun. , vol. 20, no. 3, pp. 1950–1962, Mar. 2020

work page 1950

[2] [2]

Modeling and performance ana lysis for movable antenna enabled wireless communications ,

L. Zhu, W. Ma, and R. Zhang, “Modeling and performance ana lysis for movable antenna enabled wireless communications ,” IEEE Trans. Wireless Commun. , vol. 23, no. 6, pp. 6234–6250, June 2024

work page 2024

[3] [3]

Flexible-ante nna systems: A pinching-antenna perspective,

Z. Ding, R. Schober, and H. Vincent Poor, “Flexible-ante nna systems: A pinching-antenna perspective,” IEEE Trans. Commun., pp. 1–1, 2025

work page 2025

[4] [4]

LoS blockage in pinching-antenna systems: Curse or blessing?

Z. Ding and H. V . Poor, “LoS blockage in pinching-antenna systems: Curse or blessing?” IEEE Wireless Commun. Lett. , pp. 1–1, 2025

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[5] [5]

Pinching antenna-using a dielectric waveguide as an antenna,

A. Fukuda, H. Yamamoto, H. Okazaki, Y . Suzuki, and K. Kawa i, “Pinching antenna-using a dielectric waveguide as an antenna,” NTT DOCOMO Technical J. , vol. 23, no. 3, pp. 5–12, Jan. 2022

work page 2022

[6] [6]

Pinch ing antenna systems (PASS): Architecture designs, opportunities, and outlook,

Y . Liu, Z. Wang, X. Mu, C. Ouyang, X. Xu, and Z. Ding, “Pinch ing antenna systems (PASS): Architecture designs, opportunities, and outlook,” arXiv preprint arXiv:2501.18409 , 2025

arXiv 2025

[7] [7]

QoS-aware NOMA desi gn for downlink pinching-antenna systems,

Y . Xu, Z. Ding, D. Cai, and V . W. Wong, “QoS-aware NOMA desi gn for downlink pinching-antenna systems,” arXiv preprint arXiv:2504.13723, 2025

arXiv 2025

[8] [8]

Joint transmit a nd pinching beamforming for PASS: Optimization-based or learning-based?

X. Xu, X. Mu, Y . Liu, and A. Nallanathan, “Joint transmit a nd pinching beamforming for PASS: Optimization-based or learning-based?” arXiv preprint arXiv:2502.08637 , 2025

arXiv 2025