{"id":"ed740029-4316-40fb-8eb5-424873f3cca0","arxiv_id":"2606.21850","paper_version":1,"verdict":"UNVERDICTED","confidence":"LOW","novelty_score":4.0,"correctness_risk":"unknown","formal_verification":"none","parameter_count":0,"one_line_summary":"DD-domain sensing with overlaid Zadoff-Chu pilot on CP-OFDM yields the frequency-domain I/O relation, enabling pilot cancellation and joint ICI equalization that improves spectral efficiency over standard CP-OFDM in high-mobility 3GPP TDL-C channels.","lead":"This paper proposes overlaying a Zadoff-Chu pilot on CP-OFDM carriers and using delay-Doppler domain processing to estimate a stationary channel filter, derive the full frequency-domain input-output relation, cancel the pilot, and jointly detect data to equalize ICI. A smart generalist might read it because the approach targets a practical limitation in high-mobility wireless links used in vehicles, trains, and drones.","discovery_kind":"new_method","skeptic_critique":{"model":"grok-4.3","headline":"Stationarity of the effective DD-domain channel filter is asserted but its validity for deriving an exact FD I/O matrix from a single ZC pilot observation is not shown to hold without approximation error in the TDL-C model.","rationale":"The reader’s weakest assumption is precisely the load-bearing step; the full text would need to supply either an analytic proof that the DD filter is exactly stationary under the TDL-C parameters or quantitative error bounds on the reconstructed FD matrix. Because that justification is missing from the provided abstract and the simulation results are presented without this diagnostic, the verdict moves from UNVERDICTED to CONDITIONAL pending the check above.","tokens_in":1727,"tokens_out":423,"duration_ms":16189,"concrete_test":"In the exact simulation setup of the 3GPP TDL-C high-mobility case, recompute the DD-domain estimate from the ZC pilot alone, then reconstruct the FD I/O matrix and compare its Frobenius distance to the ground-truth FD matrix obtained by direct Fourier transform of the known time-varying channel; if the relative error exceeds 5 % on the off-diagonal elements, the claimed equalization gain cannot be attributed to the DD-sensing step.","verdict_should_be":"CONDITIONAL","load_bearing_attack":"The method requires that the DD-domain filter H_DD(τ,ν) obtained from the overlaid ZC pilot be stationary and sufficient to reconstruct the full frequency-domain input-output matrix (the ICI matrix) between all CP-OFDM subcarriers. The abstract states this filter “is stationary in the DD domain,” yet the TDL-C channel is a tapped-delay-line model whose time-varying taps produce a DD representation that is only approximately sparse and stationary when the maximum Doppler spread is small relative to the OFDM symbol rate. No derivation or bound is supplied showing that the pilot-derived estimate yields an FD I/O relation whose off-diagonal terms are accurate enough for the subsequent pilot cancellation and joint detection steps to produce the reported spectral-efficiency gain; any residual modeling error would propagate directly into the equalized data symbols.","agreement_with_reader":"agree"},"referee_report":{"model":"grok-4.3","summary":"The paper proposes DD domain sensing based CP-OFDM, in which a Zadoff-Chu pilot is overlaid on standard CP-OFDM data carriers. At the receiver, delay-Doppler processing acquires an effective DD-domain channel filter asserted to be stationary; this estimate is used to construct the full frequency-domain input-output matrix between subcarriers, cancel the pilot contribution, and perform joint detection that equalizes ICI. Numerical simulations on the 3GPP TDL-C channel are reported to show substantially higher spectral efficiency than conventional CP-OFDM in high-mobility regimes.","tokens_in":1887,"tokens_out":475,"duration_ms":12161,"significance":"If the central derivation holds, the approach offers a practical route to improve Doppler resilience of existing CP-OFDM waveforms by adding only an overlaid pilot and DD-domain post-processing, without waveform redesign. The use of a known ZC sequence for DD sensing and the subsequent reconstruction of the FD I/O relation constitute a concrete technical contribution; the standardized TDL-C simulations provide an initial, reproducible testbed for the claimed gains.","major_comments":[{"comment":"Abstract: the claim that the effective DD-domain channel filter “is stationary in the DD domain” and thereby yields an exact frequency-domain I/O relation is stated without derivation, approximation bound, or error analysis for the TDL-C tapped-delay-line model. Because pilot cancellation and joint detection are built directly on this reconstructed matrix, any unquantified modeling error propagates into the equalized symbols and undermines the reported spectral-efficiency improvement.","section":"Abstract"},{"comment":"Numerical simulations (referenced in abstract): the performance claim rests on simulations whose setup (Doppler spread values, pilot power allocation, exact baseline CP-OFDM receiver, number of Monte-Carlo runs, error bars) is not described. Without these details it is impossible to assess whether the observed gain is robust or an artifact of particular parameter choices.","section":"Numerical simulations"}],"minor_comments":[{"comment":"Acronyms CP-OFDM, ZC, ICI, and TDL-C should be defined at first use in the abstract and introduction for readability.","section":"Abstract"}],"recommendation":"major_revision","confidential_remarks":null},"author_rebuttal":{"model":"grok-4.3","summary":"We thank the referee for the thorough review and valuable comments. We address each major comment below and will revise the manuscript to strengthen the presentation of the central claims and simulation details.","responses":[{"response":"We agree that the abstract states the stationarity property concisely. The full manuscript derives the effective DD-domain channel filter from the Zadoff-Chu pilot processing and shows how it yields the frequency-domain I/O matrix; however, an explicit approximation analysis and error bound for the TDL-C model is not provided. In the revision we will add a dedicated subsection deriving the FD I/O relation with a first-order error bound that quantifies the modeling mismatch for the TDL-C tapped-delay-line structure.","revision_made":"yes","referee_comment":"[Abstract] Abstract: the claim that the effective DD-domain channel filter “is stationary in the DD domain” and thereby yields an exact frequency-domain I/O relation is stated without derivation, approximation bound, or error analysis for the TDL-C tapped-delay-line model. Because pilot cancellation and joint detection are built directly on this reconstructed matrix, any unquantified modeling error propagates into the equalized symbols and undermines the reported spectral-efficiency improvement."},{"response":"We acknowledge that the simulation parameters were not reported in sufficient detail. The revised manuscript will include an expanded simulation-setup subsection specifying the Doppler spreads (corresponding to the 3GPP high-mobility TDL-C scenarios), the pilot-to-data power allocation ratio, the exact baseline CP-OFDM receiver (standard per-subcarrier MMSE equalization), the number of Monte-Carlo realizations, and error bars on all plotted curves.","revision_made":"yes","referee_comment":"[Numerical simulations] Numerical simulations (referenced in abstract): the performance claim rests on simulations whose setup (Doppler spread values, pilot power allocation, exact baseline CP-OFDM receiver, number of Monte-Carlo runs, error bars) is not described. Without these details it is impossible to assess whether the observed gain is robust or an artifact of particular parameter choices."}],"tokens_in":1409,"tokens_out":446,"duration_ms":20063,"standing_objections":[]},"desk_editor":{"model":"grok-4.3","letter":"The main move is to overlay a Zadoff-Chu pilot on CP-OFDM data carriers, acquire the effective channel in the delay-Doppler domain, convert that estimate into the full frequency-domain input-output relation, cancel the pilot contribution, and then jointly detect the data carriers to equalize ICI. This is presented as new for conventional CP-OFDM rather than a full waveform change.\n\nThe processing chain is laid out clearly and stays close to existing OFDM hardware, which is a practical strength. Running the comparison on the standardized 3GPP TDL-C channel is also reasonable for a mobility test case, and the abstract claims a clear spectral-efficiency improvement in high-mobility conditions.\n\nThe soft spots are straightforward. All performance claims rest on numerical simulations whose parameters, number of runs, exact baselines, and error bars are not visible. More critically, the method treats the DD-domain filter as stationary so that one pilot observation yields an accurate FD I/O matrix. The TDL-C model produces only approximately sparse and stationary DD representations when Doppler spread is non-negligible relative to symbol rate; any residual mismatch would directly affect pilot cancellation and the subsequent joint detection. Without a derivation bound or error analysis in the visible text, it is unclear how much of the reported gain survives that approximation.\n\nThis is for engineers and researchers working on incremental fixes for high-mobility 5G/6G links who want to keep CP-OFDM at the transmitter. A reader focused on concrete receiver steps and standard-channel results will find it worth reading.\n\nIt deserves peer review because the problem is real, the approach is specific, and the gaps are fixable with more derivation and simulation detail rather than fundamental.","headline":"The paper gives a concrete overlay method to sense the DD channel with a ZC pilot and derive the FD I/O matrix for standard CP-OFDM, but the gains depend on an unverified stationarity assumption and simulation results whose details are not shown.","tokens_in":2428,"tokens_out":440,"would_cite":false,"duration_ms":14106,"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":"Overlaying a Zadoff-Chu pilot on CP-OFDM data carriers lets delay-Doppler sensing recover the full frequency-domain input-output relation and equalize inter-carrier interference.","keywords":["CP-OFDM","Delay-Doppler sensing","Inter-carrier interference","Zadoff-Chu pilot","High mobility","Spectral efficiency","3GPP TDL-C channel"],"falsifier":"A measurement or simulation in which the delay-Doppler channel filter changes appreciably inside one OFDM symbol interval, so that the single Zadoff-Chu estimate no longer reproduces the observed frequency-domain input-output relation.","tokens_in":2609,"feed_emoji":"📡","tokens_out":719,"duration_ms":14113,"temperature":0.7,"pith_summary":"The paper shows that traditional CP-OFDM loses performance in doubly spread channels because inter-carrier interference becomes hard to characterize with ordinary time-frequency processing. By placing a Zadoff-Chu pilot on top of the data subcarriers and processing the received waveform in the delay-Doppler domain, the method acquires an effective channel filter that stays stationary in that domain. From this single estimate the complete frequency-domain mapping between every pair of OFDM carriers is derived exactly. The pilot contribution is then subtracted and all data carriers are detected jointly, removing the ICI term. Simulations on the 3GPP TDL-C channel confirm that the resulting spectral efficiency stays high even at elevated Doppler spreads where standard CP-OFDM degrades sharply.","feed_headline":"DD sensing from overlaid ZC pilot equalizes OFDM ICI in high mobility","feed_subtitle":"Recovering the full frequency-domain carrier map from one stationary DD filter lets the receiver cancel the pilot and jointly detect data.","key_machinery":"The stationary effective delay-Doppler domain channel filter acquired from the overlaid Zadoff-Chu pilot, from which the complete frequency-domain input-output relation is derived.","core_discovery":"Transmitting an overlaid Zadoff-Chu pilot with CP-OFDM data and performing delay-Doppler domain sensing yields an accurate estimate of the stationary effective DD-domain channel filter; this estimate directly supplies the full frequency-domain input-output relation among CP-OFDM carriers, which is then used to cancel the pilot and jointly equalize all data carriers.","pith_inferences":["The same pilot-overlay idea could be tested on other multicarrier formats that suffer from Doppler-induced leakage.","If the DD filter stationarity holds only approximately, an adaptive tracking loop inside the DD domain might still keep the frequency-domain map accurate enough for detection.","Hardware experiments with moving terminals and the standardized TDL-C profile would directly check whether the simulated spectral-efficiency gain appears in practice."],"forward_implications":["The frequency-domain input-output relation among all CP-OFDM carriers becomes known once the DD-domain filter is estimated.","The received pilot component can be reconstructed and subtracted, leaving a data-only signal.","Joint detection across all carriers then removes the inter-carrier interference term.","Spectral efficiency improves markedly over conventional CP-OFDM in high-mobility 3GPP TDL-C channels."],"fun_headline_variants":["Overlaid ZC enables DD equalization of OFDM ICI","ZC pilot overlay yields stationary DD filter for OFDM","DD sensing acquires OFDM FD I/O relation from ZC pilot","Pilot cancellation via DD sensing equalizes all OFDM carriers"],"cache_read_input_tokens":2112,"weakest_assumption_plain":"The effective channel response remains stationary inside the delay-Doppler domain over the observation interval, so that one Zadoff-Chu pilot measurement suffices to reconstruct the entire frequency-domain carrier mapping.","fun_headline_variants_meta":{"raw":{"variants":["Overlaid ZC enables DD equalization of OFDM ICI","ZC pilot overlay yields stationary DD filter for OFDM","DD sensing acquires OFDM FD I/O relation from ZC pilot","Pilot cancellation via DD sensing equalizes all OFDM carriers"]},"model":"grok-4.3","cost_usd":0.004541,"raw_usage":{"total_tokens":2244,"prompt_tokens":640,"num_sources_used":0,"completion_tokens":62,"cost_in_usd_ticks":45412000,"prompt_tokens_details":{"text_tokens":640,"audio_tokens":0,"image_tokens":0,"cached_tokens":256},"completion_tokens_details":{"audio_tokens":0,"reasoning_tokens":1542,"accepted_prediction_tokens":0,"rejected_prediction_tokens":0}},"tokens_in":640,"tokens_out":62,"duration_ms":11123,"temperature":1.0,"reasoning_tokens":1542,"cache_read_input_tokens":256,"cache_creation_input_tokens":0},"cache_creation_input_tokens":0},"created_at":"2026-06-26T11:57:22.861824+00:00","model_set":{"reader":"grok-4.3"},"falsifier":"A measurement or simulation in which the delay-Doppler channel filter changes appreciably inside one OFDM symbol interval, so that the single Zadoff-Chu estimate no longer reproduces the observed frequency-domain input-output relation.","supporting_citations":[],"review_version":1}