{"id":"790647c5-cd4a-4001-9f6c-dda885f48c7c","arxiv_id":"2604.09214","paper_version":2,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":5.0,"correctness_risk":"unknown","formal_verification":"none","parameter_count":0,"one_line_summary":"Develops a physics-based frequency model for LC-RIS and a location-driven phase optimization framework that improves secrecy rates across subcarriers, validated via simulations and hardware experiments.","lead":"This paper models how liquid crystal reconfigurable intelligent surfaces change phase with frequency and proposes a location-based design to keep wideband signals secure by illuminating areas rather than single points. It could help deploy large, low-cost RIS hardware in millimeter-wave networks where full channel knowledge is unavailable.","discovery_kind":"new_method","skeptic_critique":{"model":"grok-4.3","headline":"The physics-based LC unit cell model must accurately predict frequency-dependent phase shifts for the location-only optimization to deliver claimed wideband secrecy gains.","rationale":"The reader's weakest assumption directly identifies the dependency that must hold for the location-based, model-driven design to translate from optimization to physical performance. No other internal inconsistency (e.g., in the SDP formulation or complexity claims) is evident from the provided description. The experimental validation is cited but its scope relative to the model is unclear, so the verdict moves from UNVERDICTED to CONDITIONAL pending explicit model-to-measurement agreement.","tokens_in":1838,"tokens_out":366,"duration_ms":51165,"concrete_test":"Implement the physics-based model equations from the paper and compare its predicted phase shift vs. frequency curve against direct measurements on the experimental LC-RIS unit cells at five evenly spaced frequencies across the operating band; if RMS phase error exceeds 15 degrees at any point, recompute the secrecy-rate curves with the measured response substituted for the model.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The central claim requires a single phase configuration (set via voltages) to produce effective beamforming that simultaneously maximizes secrecy rate across all subcarriers. This rests on the model correctly mapping frequency to phase response for each element so that the geometric channel model (derived from MU/eavesdropper locations) yields the intended area illumination. Any unmodeled effect—such as voltage nonlinearity, inter-element coupling, or temperature sensitivity—would cause the optimized phases to deviate from the modeled response, invalidating both the SDP solution and the heuristic. The broader-area illumination mitigates location errors but provides no protection against systematic model mismatch, which would appear as reduced secrecy in both simulation and the LC-RIS prototype.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The paper develops a physics-based model for the frequency-dependent phase response of liquid crystal (LC) unit cells in reconfigurable intelligent surfaces (RIS). It proposes a location-only phase shift optimization framework (using both SDP and a low-complexity heuristic) that illuminates a broader area around legitimate mobile users to maximize secrecy rates across all subcarriers in wideband mmWave systems while mitigating location estimation errors, without requiring full CSI. The approach is evaluated through simulations showing gains over baselines and experimental tests on an LC-RIS prototype.","tokens_in":1977,"tokens_out":607,"duration_ms":47432,"significance":"If the model and optimization hold, this addresses a practical barrier to deploying large-scale LC-RIS for secure wideband communications by avoiding full CSI acquisition and handling frequency dependence explicitly. The area-illumination strategy and scalable heuristic are useful for real-world mmWave scenarios; the inclusion of both optimal and low-complexity methods plus experimental validation on a prototype strengthens the contribution.","major_comments":[{"comment":"§3 (LC unit cell modeling): The physics-based model is load-bearing for the entire framework, as the SDP and heuristic solutions map locations to phases via this model. The manuscript should include quantitative validation metrics (e.g., phase error vs. frequency and voltage) comparing model predictions to measured data from the prototype, to confirm that unmodeled effects such as inter-element coupling or voltage nonlinearity do not invalidate the wideband secrecy claims.","section":"§3"},{"comment":"§5 (Simulation and experimental results): The central claim of improved secrecy rates across subcarriers rests on the broader-area illumination mitigating location errors. However, the results section should report explicit quantitative values (secrecy rate deltas, confidence intervals, and baseline comparisons) for both the SDP and heuristic methods under location perturbation, as the abstract provides none and the skeptic concern on model mismatch would appear here as reduced performance.","section":"§5"}],"minor_comments":[{"comment":"Abstract: Include at least one quantitative result (e.g., average secrecy rate improvement in bps/Hz) from simulations and experiments to allow readers to gauge the practical impact without reading the full text.","section":"Abstract"},{"comment":"Notation and equations: Ensure consistent definition of the secrecy rate expression across subcarriers and clarify how the area illumination radius is chosen relative to location error variance.","section":"§2 and §4"},{"comment":"Figures: Add error bars or multiple runs to simulation plots of secrecy rate vs. number of elements or SNR to demonstrate robustness.","section":"Figures in §5"}],"recommendation":"major_revision","confidential_remarks":"The experimental prototype validation is a positive aspect, but the manuscript's fit for eess.SP is strong; no obvious citation gaps noted from the abstract."},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for the positive assessment of our contributions and for the detailed feedback on the LC-RIS modeling and results sections. We address each major comment below and will incorporate revisions to strengthen the manuscript.","responses":[{"response":"We agree that explicit quantitative validation of the physics-based LC unit cell model against prototype measurements is essential to substantiate the wideband secrecy claims. In the revised manuscript, we will add a dedicated subsection (or expanded figure) in §3 that reports phase error metrics, including mean absolute phase deviation versus frequency and applied voltage, directly comparing model predictions to measured data from the LC-RIS prototype. This addition will explicitly address potential unmodeled effects such as inter-element coupling and voltage nonlinearity, confirming their negligible impact within the operating bandwidth and thereby reinforcing the validity of the subsequent optimization framework.","revision_made":"yes","referee_comment":"[§3] §3 (LC unit cell modeling): The physics-based model is load-bearing for the entire framework, as the SDP and heuristic solutions map locations to phases via this model. The manuscript should include quantitative validation metrics (e.g., phase error vs. frequency and voltage) comparing model predictions to measured data from the prototype, to confirm that unmodeled effects such as inter-element coupling or voltage nonlinearity do not invalidate the wideband secrecy claims."},{"response":"We acknowledge that the current presentation of results would benefit from more explicit quantitative reporting to clearly demonstrate the gains from area illumination under location uncertainty. In the revised §5, we will include additional tables and/or annotated plots that provide specific secrecy rate deltas (in bits/s/Hz) for both the SDP and heuristic methods, along with confidence intervals where Monte Carlo averaging is used, and direct numerical comparisons against all baselines across multiple levels of location perturbation. These enhancements will quantify the robustness benefits and directly address potential concerns regarding model mismatch by showing the performance under realistic conditions.","revision_made":"yes","referee_comment":"[§5] §5 (Simulation and experimental results): The central claim of improved secrecy rates across subcarriers rests on the broader-area illumination mitigating location errors. However, the results section should report explicit quantitative values (secrecy rate deltas, confidence intervals, and baseline comparisons) for both the SDP and heuristic methods under location perturbation, as the abstract provides none and the skeptic concern on model mismatch would appear here as reduced performance."}],"tokens_in":1505,"tokens_out":514,"duration_ms":23798,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The paper's core contribution is a physics-based model of how LC unit cells change phase with frequency, then using that to set one voltage configuration that keeps secrecy decent across the band. They optimize from user and eavesdropper locations only, by spreading the illumination over an area instead of a point, and they supply both an SDP solver and a simpler heuristic that scales better for big arrays. The experimental validation on a real LC RIS prototype is the part that stands out most.","headline":"They give a usable physics model for LC frequency response and a location-only phase design with area illumination for wideband secrecy, backed by both optimization methods and hardware tests.","tokens_in":2492,"tokens_out":173,"would_cite":false,"duration_ms":29509,"reading_group":"maybe","serious_thinker":"yes","would_accept_peer_review":true},"rs_alignment":null,"lean_confirmation":null,"pith_extraction":{"msc":[],"pacs":[],"model":"grok-4.3","headline":"Liquid crystal RISs maintain wideband secrecy by optimizing phase shifts from user and eavesdropper locations alone, illuminating areas instead of points.","keywords":["liquid crystal","reconfigurable intelligent surface","wideband","secure communication","phase shift design","millimeter wave"],"falsifier":"An experiment in which measured secrecy rates with realistic location errors fall below those of a conventional point-focused phase design at the same total power.","tokens_in":2745,"feed_emoji":"📡","tokens_out":596,"duration_ms":24519,"temperature":0.7,"pith_summary":"The paper builds a physics-based model of how liquid crystal unit cells change phase with frequency, then uses that model to set element phases across a wide band. It optimizes those phases using only the positions of legitimate users and eavesdroppers rather than full channel measurements, deliberately spreading the reflected energy over a region around each user. Two solvers are presented: a semidefinite program that gives the best secrecy and a low-complexity heuristic that scales to very large surfaces. Both are shown in simulation to raise secrecy rates over point-focused baselines, and the design is confirmed on a physical LC RIS prototype.","feed_headline":"Location-only design keeps LC RIS secure across wide bands","feed_subtitle":"Phase shifts chosen from user and eavesdropper positions illuminate areas, preserving secrecy on every subcarrier without full channel state","key_machinery":"Physics-based LC unit-cell model paired with an area-illumination phase-shift optimizer that treats locations of users and eavesdroppers as the sole inputs and is solved by either SDP or a scalable heuristic.","core_discovery":"By modeling the frequency-dependent phase response of each LC cell and then choosing phases to illuminate an area around each legitimate receiver while steering away from eavesdroppers, the surface achieves higher secrecy rates on every subcarrier even when only location data is available.","pith_inferences":["The area-illumination idea could be reused for any RIS technology whose phase response drifts with frequency.","If users move, periodic location updates would be needed but the computational cost per update stays modest.","The approach may also reduce sensitivity to small errors in eavesdropper position estimates."],"forward_implications":["Large mmWave RISs become practical for secure links because full CSI acquisition is avoided.","The same location-driven design works across multiple subcarriers without per-subcarrier retuning.","A low-complexity heuristic remains effective as the number of elements grows into the thousands.","Experimental hardware confirms that the modeled frequency variation is the dominant impairment being corrected."],"fun_headline_variants":["Location-tuned LC RIS phases secure every subcarrier in wideband","LC cell frequency model leads to position-based secure illumination","Wideband LC RIS uses locations to avoid eavesdroppers on all frequencies","Experimental LC RIS design illuminates areas for location-only secrecy"],"cache_read_input_tokens":2112,"weakest_assumption_plain":"That location coordinates alone, combined with area illumination, are enough to keep secrecy high when actual channels deviate from the assumed geometry.","fun_headline_variants_meta":{"raw":{"variants":["Location-tuned LC RIS phases secure every subcarrier in wideband","LC cell frequency model leads to position-based secure illumination","Wideband LC RIS uses locations to avoid eavesdroppers on all frequencies","Experimental LC RIS design illuminates areas for location-only secrecy"]},"model":"grok-4.3","cost_usd":0.004711,"raw_usage":{"total_tokens":2357,"prompt_tokens":730,"num_sources_used":0,"completion_tokens":67,"cost_in_usd_ticks":47112000,"prompt_tokens_details":{"text_tokens":730,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":1560,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":730,"tokens_out":67,"duration_ms":25289,"temperature":1.0,"reasoning_tokens":1560,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-05-10T17:07:55.259331+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"An experiment in which measured secrecy rates with realistic location errors fall below those of a conventional point-focused phase design at the same total power.","supporting_citations":[],"review_version":1}