{"id":"156b1b7a-3f64-4385-9638-8c13a46b313c","arxiv_id":"2506.02420","paper_version":1,"verdict":"CONDITIONAL","confidence":"MODERATE","novelty_score":4.0,"correctness_risk":"medium","formal_verification":"none","parameter_count":2,"one_line_summary":"For a two-room pinching-antenna setup, the line-of-sight user's outage probability drops sharply compared to a fixed antenna, while the non-line-of-sight user keeps diversity order one and changes little.","lead":"This paper derives outage probability formulas for pinching-antenna systems serving one line-of-sight user and one non-line-of-sight user in separate rooms, under OMA and NOMA. It shows the line-of-sight user gains strongly from antenna placement while the non-line-of-sight user does not, which matters for deciding where to deploy waveguides.","discovery_kind":"extension","skeptic_critique":{"model":"deepseek-v4-flash","headline":"The 'slightly affected' NLoS-user claim is an artifact of fixing the PA at U1's x-coordinate for U2; OMA permits moving to the waveguide edge closest to U2, and NOMA placement is unoptimized, so the conclusion is placement-dependent.","rationale":"The reader's weakest_assumption points to the same load-bearing issue: all PASS results for U2 are computed for ψ_pin_1=[x1,0,d], a placement chosen for U1. My stress-test agrees and extends it: in OMA this contradicts the paper's own 'closest to Um' placement rule, since the waveguide-constrained closest point to U2 is x=D/2; in NOMA it is an unargued operating point. The central claim has two parts: U1 benefits strongly, and U2 is only slightly affected. The first part is well supported by the distance-statistic structure and Monte Carlo validation. The second part is the vulnerable one, because the comparison between CASS and PASS for U2 is really a comparison between two particular PA positions, and the choice x=x1 has no optimality justification for U2. The diversity-order conclusion is not in doubt, since Rayleigh fading fixes U2's diversity order at 1 for any position, but the magnitude of the U2 effect is precisely what the paper claims and what the fixed placement determines. I do not elevate the NOMA SIC-condition omission or the Chebyshev-Gauss 'closed-form' labeling to the main concern: under α1=0.1 and α2=0.9 the SIC condition is automatically satisfied whenever U1's own decoding condition holds, and quadrature affects the closed-form claim rather than the qualitative outage trends. The proposed check is cheap and directly settles whether the U2 conclusion survives a more natural placement rule.","tokens_in":20399,"tokens_out":8830,"duration_ms":89497,"concrete_test":"Recompute the U2 outage probability for OMA with the antenna at the waveguide edge x=D/2 instead of x=x1, deriving the corresponding distance CDF in the style of Lemma 4 and evaluating the Theorem 3 expression at the paper's parameters (D=20m, d=5m, α=6, Rbar=1 Mbps). In parallel, for NOMA sweep the PA position x over [-D/2,D/2] and record P_pin_2^{NOMA}(x) at representative SNR values such as 80 dB, verifying with Monte Carlo. If the OMA edge placement gives an OP below the CASS curve, or differs from the plotted PASS curve by more than the small margin in Fig. 6, or if the NOMA U2 OP varies by more than a factor of two across x, then the claimed 'slightly affected' result is not robust to the placement rule.","verdict_should_be":"UNCHANGED","load_bearing_attack":"Section II-B states that in OMA the PA is moved to the position closest to the served user, i.e., ψ_pin_m, yet Eqs. (8)-(12) and Lemmas 3-4 all use ψ_pin_1=[x1,0,d] for both U1 and U2. For U2, whose room is x2∈[D/2,3D/2], the closest point on the waveguide (x∈[-D/2,D/2]) is x=D/2, so the distance distribution in Lemma 4 is not the distribution for the OMA slot-2 placement promised by the model. At the waveguide edge the squared distance is (x2-D/2)^2+y2^2+d^2, with maximum 5D^2/4+d^2, whereas Lemma 4 with x1 allows horizontal separations up to 2D, giving squared distances up to 17D^2/4+d^2. This large difference can change the moderate-SNR U2 outage probability and the claimed 'slightly degraded' comparison in Corollaries 5-6. For NOMA, the same ψ_pin_1 is imposed without any argument that x1 is a reasonable operating point for the joint U1/U2 link; a placement closer to the boundary x=D/2 trades LoS U1 gain for NLoS U2 loss, and the paper never explores this tradeoff. Diversity order 1 is not endangered because it comes from Rayleigh fading, but the size of the U2 effect is placement-dependent.","agreement_with_reader":"agree"},"referee_report":{"model":"deepseek-v4-flash","summary":"This paper analyzes the outage probability of a pinching-antenna system (PASS) with one waveguide and one pinching antenna serving two users in separate rooms: U1 in the same room as the waveguide over a line-of-sight (LoS) link, and U2 in an adjacent obstructed room over a non-line-of-sight (NLoS) link. The authors derive distance distributions for the fixed-antenna (CASS) and pinching-antenna cases, then give outage-probability expressions for OMA and NOMA, together with high-SNR asymptotics that yield diversity orders. Monte Carlo simulations in Figures 2-4 match the analytical curves as written. The paper concludes that PASS significantly improves U1's outage probability compared with CASS, while U2's outage probability has the same diversity order and is only slightly affected by antenna movement.","tokens_in":20645,"tokens_out":7799,"duration_ms":74453,"significance":"If the analysis is corrected, the paper would provide a useful outage-probability framework for PASS deployments in which waveguides are too expensive to install in every room, a realistic limitation of the PASS concept. The Monte Carlo validation of the derived expressions is a strength, and the derivations are standard with no fitted parameters. However, the central comparative claim about U2 is currently tied to a placement assumption that contradicts the stated OMA protocol, so the main conclusion about 'slight degradation' of the NLoS user is not yet established. The diversity-order results are likely robust because they follow from Rayleigh fading, but the outage levels and the direction of the PASS-versus-CASS comparison for U2 are placement-dependent.","major_comments":[{"comment":"For NOMA, the PA is fixed at ψ_pin_1 = [x1, 0, d] for both users without any optimization or justification. Since the PA location determines the path-loss distribution of the NLoS U2 link through Lemma 4, the conclusion that PA movement has 'no significant effect' on U2 is not established; a placement near x = D/2 would trade a small LoS U1 gain for a substantial U2 path-loss reduction. The paper should either optimize the PA position for the joint NOMA link, justify x1 as the operating point on physical grounds (e.g., NOMA fairness), or restrict the 'slightly affected' claim to that specific placement and show how the result depends on the placement.","section":"Section II-B1, Eqs. (8)-(9), Lemma 4, Theorem 3"}],"minor_comments":[{"comment":"The threshold for PPin,OMA1 to become zero is stated as ρ ≥ (D^4/2 + d^2)(2M Rbar - 1)/η, but the correct threshold based on Lemma 3 and Eq. (37) should use D^2/4 + d^2, not D^4/2.","section":"Proposition 3"},{"comment":"The variable substitution in Appendix D is written as z = D^2/8 t + 3D^2/8, but the integrands and the preceding derivation use z = D^2/8 t + D^2/8 + d^2. This appears to be a typographical error that should be fixed.","section":"Appendix D, Eq. (D.4)"},{"comment":"The display equation (C.3) contains garbled symbols and missing offsets: the terms √̺ and √ς are used without being properly defined in that equation, and several expressions in Lemma 4 (ℓ, ∂, κ, ̺, τ, ς) are difficult to parse. The typesetting of the piecewise PDF/CDF and of the quadrature integrands should be carefully proofread.","section":"Appendix C, Eq. (C.3)"},{"comment":"The performance-gain expressions are written as functions of an undefined variable z. Since the gains depend on the threshold a or b through FZ1, the argument should be defined explicitly to make the piecewise formulas interpretable.","section":"Eqs. (49) and (51)"},{"comment":"The statement that the U2 outage difference is 'miniscule' is made from the first-order asymptotic difference Δ∞ ∝ ρ^-1, and Figures 6(b) and 8(b) plot only the asymptotic difference. The finite-SNR U2 outage difference is not shown, so the 'slightly degraded' wording should be explicitly qualified to the high-SNR regime unless finite-SNR curves are provided.","section":"Corollaries 5-6 and Section V-B"},{"comment":"The expressions described as 'closed-form' are Chebyshev-Gauss quadrature sums whose accuracy depends on the chosen number of nodes n. Calling them closed-form is misleading; the abstract and contributions should describe them as semi-analytical approximations with a controllable quadrature error. This does not affect the simulation validation, which is a strength of the paper.","section":"Abstract and Theorems 1-4"}],"recommendation":"major_revision","confidential_remarks":"The paper is within the journal's scope, and I did not find citation-pattern or novelty concerns. The key technical issue is the placement inconsistency for the OMA U2 link, which is fixable but may change the paper's second main conclusion. The NOMA SIC-condition omission and the placement-dependence of the NOMA U2 result should also be addressed before the manuscript can be accepted."},"author_rebuttal":null,"desk_editor":{"model":"deepseek-v4-flash","letter":"Short version: the paper gives a genuinely new outage analysis for a two-room pinching-antenna setup with one LoS and one NLoS user, and the Monte Carlo matches the formulas. But the OMA analysis does not do what the model says it does, and that undermines the headline claim that NLoS users are only slightly affected.\n\nWhat's new: the distance statistics for a PA at U1's x-coordinate serving U2 in an adjacent room (Lemmas 3 and 4) are new, and the diversity-order results (all diversity-one for NLoS, zero asymptotic OP for LoS) are correct and cleanly derived. The quadrature expressions are honest numerical integration, though calling them closed-form is a stretch. The paper is also careful to validate against simulation.\n\nThe soft spots, in order of importance. First, Section II-B says the PA moves to the closest position for the served user, but for OMA slot 2 the analysis keeps the PA at U1's x-coordinate. For U2 the closest waveguide point is x=D/2, which gives a different distance distribution with much smaller maximum separation. So the U2 outage probability in Theorem 3 is not the outage of the described system, and the comparison in Corollary 5 (and the 'slightly degraded' claim) is an artifact of a fixed, suboptimal placement. For NOMA the placement is a choice, but the paper never justifies x1 or explores the tradeoff; the same claim is therefore not robust. Second, the NOMA outage for U1 ignores the SIC decoding condition: the event should require both R_{1,2} and R_1 above threshold. In the stated parameter regime this is probably numerically minor, but it should be stated and checked. Third, there are typos in Propositions 3 and 4 (the 'becomes zero' statements refer to U1, not U2). None of this destroys the diversity-order conclusion, which comes from the Rayleigh fading and is solid.\n\nWho is this for? Researchers working on pinching-antenna performance analysis; it is a useful reference for the two-room geometry. It deserves a serious referee, but it needs revision first: rewrite the OMA slot-2 analysis with the correct placement, fix the SIC condition, and soften the 'slightly affected' claim to 'for the considered placement.'","headline":"Fresh two-room outage analysis for pinching antennas, but the OMA equations don't match the stated PA placement, so the 'slightly degraded NLoS' claim is not yet established.","tokens_in":21240,"tokens_out":5533,"would_cite":false,"duration_ms":48344,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"deepseek-v4-flash","headline":"One movable pinching antenna reduces outage for the line-of-sight user while leaving the non-line-of-sight user's diversity order unchanged.","keywords":["pinching-antenna systems","non-orthogonal multiple access","orthogonal multiple access","outage probability","diversity order","line-of-sight link","non-line-of-sight link","movable antenna"],"falsifier":"In the two-room geometry with $D=20$ m, $d=5$ m, and $\\alpha=6$, simulate the non-line-of-sight user's outage at high SNR while sweeping the pinching antenna's x-coordinate across the waveguide; if some position away from the line-of-sight user's x-coordinate makes that user's outage drop appreciably below the paper's PASS curve, or makes the gap to the fixed-antenna system grow with SNR rather than vanish, then the claim that antenna movement barely affects the NLoS user is not the whole story.","tokens_in":20143,"feed_emoji":"📡","tokens_out":8751,"duration_ms":77413,"temperature":0.7,"pith_summary":"This paper asks whether a single movable antenna on a ceiling waveguide can serve two users in separate rooms, one with a direct line of sight and one without, under time-sharing (OMA) and power-domain NOMA. The answer it argues for is yes, but with an asymmetry: moving the antenna to the line-of-sight user's position lowers that user's outage probability substantially compared with a fixed antenna at the room center, while the blocked user's outage is only slightly affected and keeps the same diversity order. To make the case, the paper derives closed-form outage probabilities for both users in both access schemes, adds high-SNR approximations that expose the diversity orders, and confirms the formulas by simulation. The finding matters because waveguides are expensive enough that not every room will have one, so a practical pinching-antenna deployment needs to know what happens to users beyond the line-of-sight service area.","feed_headline":"One movable antenna cuts outage for the line-of-sight user","feed_subtitle":"Line-of-sight link outage vanishes at high SNR; blocked link keeps diversity order one.","key_machinery":"The load-bearing machinery is a set of distance-statistic distributions. Lemmas 1 and 2 give the squared-distance distributions from the fixed center antenna to the two users; Lemmas 3 and 4 give the corresponding distributions from the pinching antenna, which is always placed at $\\psi_1^{\\mathrm{pin}} = [x_1,0,d]$. Because the line-of-sight link has no fading, its outage probability is the CDF of the squared distance evaluated at a threshold; because the non-line-of-sight link is Rayleigh, its outage probability is an integral of the exponential fading CDF against the distance PDF. The high-SNR propositions expand the exponential term and keep the first-order term, which is what yields diversity order one for the non-line-of-sight user and zero outage for the line-of-sight user at sufficiently high SNR.","core_discovery":"On the paper's own terms, the central discovery is that the line-of-sight user's outage in a pinching-antenna system is a purely geometric event: because there is no small-scale fading on that link, the user is in outage only when the squared distance from the pinching antenna exceeds a threshold set by the SNR, target rate, and carrier frequency. Moving the antenna to the user's x-coordinate makes the distance distribution concentrate near $d^2$, so the outage probability can be driven exactly to zero beyond a finite SNR threshold. For the non-line-of-sight user, Rayleigh fading makes the outage probability an average of an exponential tail over the distance distribution, and the high-SNR expansion gives $P \\approx c\\rho^{-1}$, so the diversity order is one whether the antenna is fixed or moved. Theorems 1 through 4 give the exact closed-form outage expressions, and Propositions 1 through 4 give the asymptotic coefficients that expose the diversity orders.","pith_inferences":["The paper fixes the antenna at the line-of-sight user's x-coordinate for all schemes; an optimization over antenna position for the non-line-of-sight user might turn the reported slight degradation into an improvement, or expose a trade-off that the paper's one-dimensional comparison does not capture.","Because the non-line-of-sight user's outage has diversity order one, adding a second pinching antenna and selecting the better one would likely raise that diversity order to two; this is a direct but unexamined consequence of the distance-averaging mechanism.","For fixed-rate traffic, the paper's formulas imply that system reliability at high SNR is governed almost entirely by the non-line-of-sight tail, so the simple $c\\rho^{-1}$ asymptotics could be used to dimension transmit power without full Monte-Carlo simulation."],"forward_implications":["In both OMA and NOMA, a single movable pinching antenna reduces the line-of-sight user's outage probability relative to a fixed center antenna, with the largest reduction in the middle SNR regime.","The non-line-of-sight user's outage probability keeps diversity order one in both fixed and pinching systems, and the difference between the two is on the order of $\\rho^{-1}$, vanishing as the SNR grows.","In the pinching-antenna system, NOMA still delivers the familiar fairness trade: the line-of-sight user is slightly worse than under OMA while the non-line-of-sight user is better.","The closed-form expressions are computationally light, with Chebyshev-Gauss quadrature at $n=100$ nodes giving a negligible approximation error.","The performance gain of the pinching antenna over the fixed antenna is maximized in the middle SNR regime and shifts with room size without changing the diversity order."],"supporting_citations":[{"why":"Supplies the spherical-wave channel model and the flexible-antenna system setup that the paper adapts to its OMA and NOMA rate expressions.","marker":"[22]"},{"why":"Provides the earlier closed-form outage and ergodic-rate analysis of pinching-antenna systems that this work extends to mixed LoS and NLoS rooms.","marker":"[18]"},{"why":"Defines the pinching-antenna architecture and the waveguide-cost constraint that motivates restricting the waveguide to one room.","marker":"[2]"},{"why":"Documents the use of pinching antennas to mitigate signal blockage, grounding the adjacent-room NLoS scenario.","marker":"[16]"},{"why":"Supplies the NOMA fixed-power-allocation fairness convention used when setting $\\alpha_1 < \\alpha_2$.","marker":"[13]"},{"why":"Discusses NOMA-based pinching-antenna systems in multi-user settings, providing the background that NOMA improves spectral efficiency when waveguides are scarce.","marker":"[23]"}],"fun_headline_variants":["Move antenna, erase LoS outage at high SNR","Pinching antenna drives LoS outage to zero","LoS outage vanishes; NLoS stays at diversity one","Antenna movement cuts direct-link outage, not blocked link","Zero outage for LoS with antenna movement"],"cache_read_input_tokens":3200,"weakest_assumption_plain":"The analysis assumes the pinching antenna is always moved to the line-of-sight user's x-coordinate, and that same placement is used for the non-line-of-sight user's link, without optimizing or justifying the choice.","fun_headline_variants_meta":{"raw":{"variants":["Move antenna, erase LoS outage at high SNR","Pinching antenna drives LoS outage to zero","LoS outage vanishes; NLoS stays at diversity one","Antenna movement cuts direct-link outage, not blocked link","Zero outage for LoS with antenna movement"]},"model":"deepseek-v4-flash","effort":"low","cost_usd":0.000673,"raw_usage":{"total_tokens":3096,"prompt_tokens":1009,"completion_tokens":2087,"prompt_tokens_details":{"cached_tokens":384},"prompt_cache_hit_tokens":384,"prompt_cache_miss_tokens":625,"completion_tokens_details":{"reasoning_tokens":2012}},"tokens_in":625,"tokens_out":2087,"duration_ms":14140,"temperature":1.0,"reasoning_tokens":2012,"cache_read_input_tokens":384,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-08-07T11:25:07.878883+00:00","model_set":{"reader":"deepseek-v4-flash"},"falsifier":"In the two-room geometry with $D=20$ m, $d=5$ m, and $\\alpha=6$, simulate the non-line-of-sight user's outage at high SNR while sweeping the pinching antenna's x-coordinate across the waveguide; if some position away from the line-of-sight user's x-coordinate makes that user's outage drop appreciably below the paper's PASS curve, or makes the gap to the fixed-antenna system grow with SNR rather than vanish, then the claim that antenna movement barely affects the NLoS user is not the whole story.","supporting_citations":[{"cited_title":"Flexible-antenna s ystems: A pinching-antenna perspective,","cited_arxiv_id":null,"evidence_quote":"Supplies the spherical-wave channel model and the flexible-antenna system setup that the paper adapts to its OMA and NOMA rate expressions."},{"cited_title":"(2021) Pinching An- tenna","cited_arxiv_id":null,"evidence_quote":"Documents the use of pinching antennas to mitigate signal blockage, grounding the adjacent-room NLoS scenario."},{"cited_title":"Non- orthogonal multiple access (NOMA) with multiple intellige nt reflecting surfaces,","cited_arxiv_id":null,"evidence_quote":"Supplies the NOMA fixed-power-allocation fairness convention used when setting $\\alpha_1 < \\alpha_2$."}],"review_version":1}