Signal Processing
Prognostic Value of Lung Ultrasound Biomarkers for Readmission Risk in Congestive Heart Failure: A Pilot Data-Driven Analysis
Jana Armouti, Laura Hutchins, Jacob Duplantis et al. (+12 more)
Hospital readmission within 30 days of discharge is a leading driver of morbidity, mortality, and avoidable healthcare expenditure in congestive heart failure (CHF). Current clinical risk stratification tools rely primarily on non-imaging data and exhibit limited predictive performance. Point-of-care lung ultrasound (LUS) offers a sensitive, noninvasive window into the pulmonary congestion that characterizes CHF decompensation, yet its prognostic utility for readmission prediction remains largely unexplored. We present a pilot feasibility study, the first systematic machine learning study using B-mode LUS acquired during hospitalization to predict 30-day CHF readmission. Quantitative spatiotemporal
embeddings are extracted from a pretrained Temporal Shift Module (TSM) ResNet-18 encoder, and interpretable biomarker features are separately evaluated. Through structured ablations over lung view, temporal representation, multi-view fusion, and cross-lung augmentation, we identify the key imaging factors driving readmission risk. Our findings reveal that (1) dependent lower-lung regions (Left-3, Right-3) carry the strongest prognostic signal, consistent with their greater susceptibility to hydrostatic congestion; (2) temporal difference features between sequential examinations substantially outperform single-timepoint representations, highlighting the importance of capturing disease trajectory; and (3) multi-view feature concatenation yields the best overall performance, with our top MLP model achieving an F1 score of 0.80 (95% CI: 0.62-0.96). Biomarker analysis further reveals that pleural-line abnormalities, including breaks and indentations, are as informative as the canonical A-line and B-line markers. These results support POCUS-derived biomarkers as practical, interpretable tools for noninvasive CHF risk stratification.
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All authors Jana Armouti, Laura Hutchins, Jacob Duplantis, Thomas Deiss, Thales Nogueira Gomes, Keyur H. Patel, Seema Walvekar, Shane Guillory, Thomas H. Fox, Amita Krishnan, Ricardo Rodriguez, Bennett DeBoisblanc, Deva Ramanan, John Galeotti, Gautam Gare
Systems and Control
Replicating Real-World 23-Hz Oscillations Caused by Large Electronic Loads
Lingling Fan, Ali Yazdanpanah, Yunzhi Cheng et al. (+4 more)
In 2024, Texas operators observed 23-Hz oscillations in real power measurements close to a large electronic load (LEL). Oscillations emerged when the load's power consumption reached approximately 320 MW level and subsided as the active power demand decreased. The paper aims to analyze the event and reproduce the oscillations using electromagnetic transient (EMT) simulations. In the first stage, a representative feedback system is developed, and frequency-domain analysis is conducted to examine the phenomenon and identify its key influencing factors. Next, detailed EMT simulations are performed to further validate the proposed analytical approach. The results show that the feedback system effectively captures and characterizes the critical features of the 23-Hz oscillation incident. In addition, the EMT simulations successfully reproduce the real-world event, with the simulated results closely matching the fault recorder data.
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All authors Lingling Fan, Ali Yazdanpanah, Yunzhi Cheng, Zhixin Miao, Farshid Salehi, Patrick Gravois, Shun-Hsien Huang
Image and Video Processing
RDDM: A Residual-Driven Drifting Model for High-Fidelity Low-Dose CT Denoising
Jianxu Wang, Qing Lyu and Ge Wang
Low-dose CT (LDCT) denoising remains an important yet challenging problem in medical imaging. Although recent learning-based methods have shown promising performance, those optimized using classical pixel-level objectives often produce over-smoothed reconstructions. Existing mainstream generative models, such as
diffusion models, have improved fidelity at the cost of expensive multi-step iterative inference, which limits their practicality for real-time use. To address this gap, we propose a Residual-Driven Drifting Model (RDDM) for effective, efficient, and high-fidelity LDCT denoising. Inspired by the recently proposed Drifting Models, RDDM incorporates the multi-step distribution
evolution into the training dynamics through a residual drifting field, thereby enabling one-step denoising. Specifically, the residual drifting field is formed by an attractive force induced by the residuals between LDCT and normal-dose CT (NDCT) and a repulsive force induced by the generated residuals. In addition, by adjusting the parameter settings and incorporating pixel-level supervision, we develop three RDDM variants, covering application needs from detail preservation to stronger noise suppression. Extensive experiments demonstrate that RDDM achieves state-of-the-art denoising performance among supervised baselines. In particular, RDDM-Fine produces reconstructions that are highly consistent with NDCT, achieving superior PSNR and SSIM together with the best FID of 5.87 while preserving realistic anatomical textures. Moreover, RDDM enables on-the-fly inference, requiring only about 15 ms to denoise a single 512 x 512 LDCT slice. These results establish RDDM as a promising solution for high-fidelity and real-time LDCT denoising in clinical applications.
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Signal Processing
A reversed solar illumination dependence of unintended emission from Starlink Direct-to-Cell satellites at 72-234 MHz with the EDA2
Haofan Dong, Houtianfu Wang, Hanlin Cai et al. (+1 more)
Second-generation Starlink Direct-to-
Cell (DTC) satellites carry an additional payload for direct cellular phone connectivity whose unintended electromagnetic radiation (UEMR) at sub-300 MHz frequencies has not been individually characterised. We reanalyse 112,534 detections from 1,806 Starlink satellites observed with the Engineering Development Array version 2 (EDA2) at 21 frequencies between 72.685 and 234.375 MHz (Grigg et al. 2025), separating 175 DTC and 1,623 Ku-only v2-Mini comparison satellites via the McDowell General Catalogue (McDowell 2020). DTC satellites emit a range-corrected flux density 1.45x that of the Ku-only comparison (Cliff's delta = +0.30, p = 2.6e-11). At 230.469 MHz the XX detection fraction reaches 0.811 against a 0.481 baseline (p ~ 1e-274), and 11 of 21 frequency channels show Benjamini-Hochberg-significant polarisation anomalies. The DTC population is brighter in eclipse than in sunlight (illuminated/eclipsed flux density ratio 0.47) while the Ku-only comparison shows the opposite sense (1.18); the reversal persists across altitude, sub-satellite latitude, frequency, and launch-epoch matching. The reversal strongly disfavours UEMR mechanisms that scale monotonically with instantaneous
solar photocurrent and favours an active on-board source whose effective duty cycle is larger at lower
equilibrium temperature. Within the 230.469 MHz coarse channel, fine-channel inspection isolates the excess to a single ~24 kHz bin near 230.627 MHz, tail-driven and absent at five control channels. Three falsifiable mechanism-discrimination tests show this feature is not coincident with the LOFAR-resolved Bassa et al. (2024) clock fundamentals, is unresolved at the EDA2 24 kHz resolution, and is heterogeneously expressed across the v2-Mini fleet rather than driven by a few permanently bright units or by uniform thermal scaling.
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All authors Haofan Dong, Houtianfu Wang, Hanlin Cai, Ozgur B. Akan
Systems and Control · Cross-listed from cs.CE
Weighted Flow Matching and Physics-Informed Nonlinear Filtering for Parameter Estimation in Digital Twins
Yasar Yanik, Himadri Basu, Ricardo G. Sanfelice et al. (+1 more)
Digital twins (DTs) rely on continuous synchronization between physical systems and their virtual counterparts through online parameter estimation under uncertainty. In many practical settings, however, this task is challenged by low observability, weak excitation, nonlinear dynamics, and noisy or biased measurements. In this work, we develop a new mathematical framework that integrates Weighted Flow Matching (WFM) generative modeling with physics-informed nonlinear filtering to enhance parameter estimation in DTs. WFM relies on dynamic reweighting of training samples, which guides the generative model toward parameter regimes most informative of the evolving system state. This generative component is tightly coupled with a physics-informed filtering architecture based on the Unscented Kalman Filter (UKF), yielding a unified DT framework that combines data-driven probability transport with physically consistent state and parameter estimation. The effectiveness of the new integrated framework is demonstrated within a spacecraft DT architecture, where stable moment of inertia estimation is achieved under uncertain and noisy sensing, with significant performance improvements over established approaches such as Extended Kalman Filtering (EKF) and Ensemble Kalman Filtering (EnKF). These results highlight the potential of weighted generative modeling as a core mechanism for real-time DT synchronization in operational and mission-critical systems.
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All authors Yasar Yanik, Himadri Basu, Ricardo G. Sanfelice, Daniele Venturi
Signal Processing · Cross-listed from stat.ME
Symmetry-Aware Convex Shrinkage for High-Dimensional Covariance Estimation
Mitchell A. Thornton
We develop a class of data-adaptive shrinkage
estimators for high-dimensional covariance estimation in which the shrinkage target is a Reynolds projection of the sample covariance under a finite
symmetry group selected from a candidate library by held-out predictive performance. The class generalizes the convex shrinkage
estimator of Ledoit and Wolf by replacing the scalar-identity target with a structured target derived from a
symmetry group when one is available, and generalizes the group-symmetric maximum-likelihood
estimator of Shah and Chandrasekaran by combining structural targeting with adaptive convex shrinkage and by selecting the group from data rather than treating it as prespecified. A two-tier procedure performs the group selection: a universal per-candidate evaluation based on held-out negative log-likelihood, optionally preceded by a domain-specific step that constructs the candidate library from structural priors. We establish a finite-sample regret bound for the held-out calibration of the convex combination weight, an oracle inequality for the data-driven group selection, and a quantitative sufficient-match condition under which the proposed
estimator dominates Ledoit-Wolf shrinkage in Frobenius mean-squared error. The procedure is illustrated on six real-data problems spanning finance (S&P~500 daily returns),
climate (NOAA OISST sea-surface temperature anomalies), genomics (TCGA-BRCA gene expression),
radio signal processing (RadioML 2018.A), astronomical imaging (
Galaxy10 DECaLS), and natural image patches (CIFAR-10 with a CIFAR-10.1 distribution-shift companion). An empirical comparison is also made against the
Bayesian permutation-
symmetry estimator of Chojecki and colleagues. Outside the few-shot regime, where structural priors carry the most information per observation, Ledoit-Wolf shrinkage remains the appropriate baseline.
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Systems and Control
Geometric Fault Identification via Mirror Descent Learning
Mahdi Taheri, Haeyoon Han, Soon-Jo Chung et al. (+1 more)
This paper develops a fault detection and identification (FDI) method for nonlinear control-affine systems under simultaneous actuator and sensor faults. We adopt a
geometric approach to study the isolability of faults in the sense of the principal angles between subspaces corresponding to each actuator and sensor fault. As for the fault identification, a hybrid
estimator that consists of a Luenberger-like observer with contraction guarantees is developed. Moreover, neural networks are embedded in the mentioned observer to estimate actuator and sensor faults. Considering that the training
dataset for neural networks cannot be representative of every fault scenario, the last layer of each network is adapted using mirror descent-based laws. The mirror descent-based adaptive laws impose isolability conditions for fault channels and do not assume a quadratic parameter estimation space to consider the geometry of the fault subspaces. A Lyapunov-based analysis establishes that the state and parameter estimation errors are uniformly ultimately bounded. The effectiveness of our proposed FDI method is illustrated on the 3-axis attitude control system of a spacecraft.
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All authors Mahdi Taheri, Haeyoon Han, Soon-Jo Chung, Fred Y. Hadaegh
Signal Processing
Connectionless Bluetooth Channel Sounding via PAwR for Scalable and Energy-Efficient Ranging
Leon Schex, Markus Cremer and Uwe Dettmar
Bluetooth Core Specification v6.0 introduces Channel Sounding (CS) as a high-accuracy ranging primitive for Bluetooth Low Energy, but standard operation requires per-pair connections. This entails multistage initiation and limits concurrent partners per
radio. We present a connectionless CS architecture combining the LE CS Test command with Periodic Advertising with Responses (PAwR). A Central Orchestrator, a gateway, and synchronized CS devices provide application-layer coordination, configuration
alignment, and result aggregation. Each device derives its role, deterministic random bit generator initialization state, channel sequence, and response slot assignment from its device index and a Peer-to-Peer Assignment
Matrix. The
matrix can be updated per cycle to reconfigure arbitrary device-to-device pairings within each subevent group. An nRF54L15 proof-of-concept evaluation shows that deterministic channel management eliminates collision-induced outliers under simulated dense-deployment channel overlaps. Compact serialization omits fields recoverable from the measurement configuration, reducing the ranging-data payload by 68%-69% and enabling complete result reporting through PAwR response slots. For one measured partner per 1-s update cycle, the proposed architecture reduces steady-state active charge by up to 25% relative to a fair connected baseline in the optional Real-time Ranging Data mode and up to 48% in the mandatory On-demand Ranging Data mode. For a partner switch, receiving and processing a configuration payload requires approximately 97% less charge than the connected initiation procedure. A component-based 24-h model projects up to 88% lower charge when all four partners are replaced every update, while a timing-based capacity analysis projects up to 14080 active devices per PAwR train for a four-measurement workload.
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Audio and Speech Processing · Cross-listed from cs.SD
Taming Audio VAEs via Target-KL Regularization
Prem Seetharaman and Rithesh Kumar
Latent
diffusion models have emerged as the dominant paradigm for many generation tasks including audio generation such as text-to-audio, text-to-music and text-to-
speech. A key component of latent
diffusion is an autoencoder (VAE) that compresses high-dimensional signals into a low frame rate continuous representation that is conducive for downstream prediction. Regularizing these VAEs is challenging, as there is a trade-off between over-regularized (poor output quality) and under-regularized (difficult to predict) latent representations. We propose a framework for studying this trade-off through compression and train Audio VAEs at specific bitrates via target-KL regularization. This allows direct comparison to well-studied discrete neural audio codec models, and the construction of rate-distortion curves for audio VAEs. We evaluate the impact of target-KL regularization on text-to-sound generation and find that sweeping compression rates is helpful in identifying the optimal generation setting.
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Systems and Control
A review of imbalance price forecasting in Europe: algorithms, metrics and the way forward
Arnaud Verstraeten, Maria Margarida Mascarenhas and Hussain Kazmi
Renewable electricity generation has grown significantly across many European power systems, leading to a greener energy mix, but also additional complexity in balancing electricity supply and demand. Unexpected differences between forecasts and actual output can lead to fluctuations in the system imbalance, which causes volatile imbalance prices. Accurate imbalance price forecasts are crucial for
market players to choose a strategic balancing position. In early works, most
forecasting methods combined fundamental and statistical approaches, but currently there is a clear trend towards data-driven machine learning models. This review compares
forecasting algorithms in European
markets with a focus on methodology. We emphasize the importance of high-quality input data, including intraday information and per-minute system data. Next, we identify the need for a common
benchmark to compare novel
forecasting methods developed for different
markets and time periods. Finally, we argue that forecasts should be evaluated in terms of both downstream value and accuracy.
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Systems and Control
Ensuring reliability in 100% renewable microgrids: a scenario-based joint planning and operational design framework
Mohammed Zeehan Saleheen, Markus Wagner and Hao Wang
Off-grid microgrids powered entirely by renewable energy sources face substantial challenges in achieving utility-grade reliability standards. Existing microgrid planning frameworks often prioritize cost minimization while treating reliability as a secondary metric, thereby leading to suboptimal designs. This paper presents a comprehensive scenario-based optimization framework that simultaneously addresses long-term capacity planning and short-term operational dispatch in two stages for 100%-renewable microgrids. The developed two-stage
stochastic programming model co-optimizes the investment and operation of photovoltaic generation and battery energy storage, while ensuring compliance with stringent reliability constraints following utility grid standards. Network modeling with operational constraints, such as line capacities and voltage limits, is incorporated to allow distributed resource placement leveraging power sharing between microgrid nodes. A novel scenario generation approach captures critical uncertainties, including seasonal demand fluctuations,
solar output variations, and probabilistic equipment failures, through the statistical clustering of historical data. The optimization framework integrates utility-grade reliability constraints limiting the expected energy not served to below 0.002% of the annual demand while minimizing the total system costs. Numerical simulations demonstrate the effectiveness of the proposed framework, achieving 99.998% supply reliability using only photovoltaic power and battery energy storage. The optimized network-aware distributed resource allocation provides inherent resilience through power rerouting during component outages, maintaining load continuity even under simultaneous equipment failures. This study confirms the feasibility of 100%-renewable microgrids to support remote communities while meeting utility-grade reliability
benchmarks.
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Systems and Control
Empirical evaluation of Time Series Foundation Models for Day-ahead and Imbalance Electricity Price Forecasting in Belgium
Chi Bui, Maria Margarida Mascarenhas, Arnaud Verstraeten et al. (+1 more)
Recent advances in Time Series Foundation Models (TSFMs) promise zero-shot
forecasting capabilities with minimal task-specific training. While these models have shown strong performance across generic
benchmarks, their applicability in volatile, complex electricity
markets remains underexplored. Addressing this gap, this study provides a systematic empirical evaluation of several TSFMs, specifically Chronos-2 and Chronos-Bolt (developed by Amazon), and TimesFM 2.5 (provided by Google), for
forecasting Belgian day-ahead and imbalance electricity prices. For both considered
markets, Chronos-2 in ARX mode produces the most accurate forecasts. Compared with the best ensemble prediction from other machine learning methods, Chronos-2's Mean Absolute Error (MAE) is 5% lower for the day-ahead
market. In contrast, the model yields 10% higher MAE predicting imbalance prices across all forecast horizons, except for the two-hour-ahead horizon. Moreover, we find that TSFMs exhibit genuine zero-shot
forecasting skills but still struggle under extreme
market conditions.
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All authors Chi Bui, Maria Margarida Mascarenhas, Arnaud Verstraeten, Hussain Kazmi
Systems and Control · Cross-listed from cs.AI
Reliability and Effectiveness of Autonomous AI Agents in Supply Chain Management
Carol Xuan Long, David Simchi-Levi, Feng Zhu et al. (+3 more)
This paper studies the performance and reliability of autonomous generative AI
agents in multi-echelon supply chains using the MIT Beer Game. We examine how model choice, operational guardrails, centralized data sharing, and
prompt design affect system performance. In our best-performing configuration, GenAI
agents reduce total supply-chain costs by up to 80% relative to human teams. Despite strong average performance, autonomous
agents can exhibit substantial run-to-run instability, generating volatile procurement decisions and large tail costs. We characterize this phenomenon as
agent bullwhip, the amplification of decision instability in autonomous multi-
agent systems. We show that this instability can propagate across echelons and compound over time, even when the underlying demand path is held fixed. We then evaluate two approaches for improving reliability: reinforcement-learning post-training and operational guardrails. Both reduce tail events and mitigate
agent bullwhip, but they operate through different mechanisms and require different levels of information and model access. Reinforcement-learning post-training delivers the largest gains in reliability and system performance when system-level feedback is available, while guardrails provide a simple training-free alternative for constraining extreme decisions.
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All authors Carol Xuan Long, David Simchi-Levi, Feng Zhu, Huangyuan Su, Andre P. Calmon, Flavio P. Calmon
Signal Processing
Design and Practical Validation of a Novel Modulation Scheme for RIS Detection and Identification
Aymen Khaleel, Adam Umra and Aydin Sezgin
The reconfigurable intelligent surfaces detection and identification (RISs-ID) is a critical process that enables a base station (BS) to adaptively assign the appropriate RIS to a given \ac{UE}. This work proposes a novel modulation scheme to enhance the reliability of RIS-ID by reducing the miss-detection ($P_\text{m}$) and false-alarm ($P_\text{f}$) probabilities. Specifically, we leverage the RIS's passive beamforming gain to enable over-the-air modulation of the RIS ID, combined with passive beam sweeping to extend detection coverage in angular space. Prototype experiments demonstrate the effectiveness of the proposed scheme in reducing $P_\text{m}$ and $P_\text{f}$ to $10^{-3}$ across different operating points.
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Image and Video Processing · Cross-listed from cs.GR
A Single Atlas is All You Need: Decoder-Side Gaussian Splatting for Immersive Video
Dawid Mieloch and Stuart Perry
Immersive
video delivery is bottlenecked by pixel-rate constraints, making the transmission of high-resolution depth maps or explicit 3D volumetric data expensive. Decoder-Side Depth Estimation (DSDE) shifts depth computation to the client, but struggles with complex geometries, inter-view flickering, and non-Lambertian reflections. Conversely, 3D Gaussian Splatting (3DGS) offers state-of-the-art view synthesis, but transmitting splats (or their projected 2D maps) incurs prohibitive bandwidth costs and is poorly aligned with standard
video codecs. We propose Decoder-Side Gaussian Splatting (DSGS), a framework that natively replaces the depth-estimation stage of DSDE with feed-forward 3DGS inference, optimizing volumetric scenes entirely on the decoder side from compressed textures and metadata. A central, counterintuitive finding is that lossy compression acts as an implicit low-pass filter stabilizing feed-forward splat prediction: compressed bitstreams exceed lossless quality while shrinking tenfold. Under extreme view sparsity (one 2D atlas comprising 4 input views), DSGS achieves a +5.79 dB BD-PSNR and +0.054 BD-SSIM gain over the DSDE anchor while reducing maximum inter-view Delta IV-PSNR from 17.2 dB to 6.4 dB, minimizing the domain shift between transmitted and virtual viewports.
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Audio and Speech Processing
SemaVoice: Semantic-Aware Continuous Autoregressive Speech Synthesis
Huimeng Wang, Hui Lu, Jiajun Deng et al. (+7 more)
Continuous autoregressive
speech synthesis has recently emerged as a promising direction for zero-shot text-to-
speech (TTS). However, existing methods still suffer from a fundamental mismatch between semantic-prosodic modeling and reconstruction-driven continuous
speech representations. This mismatch causes TTS models to focus excessively on low-level acoustic textures at the expense of high-level semantic coherence, further exacerbating error accumulation in autoregressive generation. To address this challenge, we propose SemaVoice, a semantic-aware continuous autoregressive framework for high-fidelity zero-shot TTS. SemaVoice introduces a
Speech Foundation Model (SFM) guided
alignment mechanism that refines continuous
speech representations to better capture both local semantic consistency and global structural relationships. These representations condition a patch-wise
diffusion head within the autoregressive framework for high-quality
speech synthesis. Experimental results on the Seed-TTS
benchmark show that SemaVoice achieves an English WER of 1.71% and remains highly competitive with state-of-the-art open-source systems in both objective and subjective evaluations. The effectiveness of SFM guided
alignment is further confirmed by significant improvements under varying representation granularities with a fixed information-rate constraint.
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All authors Huimeng Wang, Hui Lu, Jiajun Deng, Haoning Xu, Youjun Chen, Xueyuan Chen, Zhaoqing Li, Shuhai Peng, Shiyin Kang, Xunying Liu
Systems and Control
Over-approximation of weakly-hard constraints for control systems verification (Extended)
Rieke de Maeyer, Holger Hermanns and Martina Maggio
A hard real-time system cannot miss any deadline. A weakly-hard real-time system, on the contrary, is designed to tolerate a specific number of deadline misses. For instance, the AnyMiss(2, 300) weakly-hard constraint stipulates that in every window of 300 consecutive jobs, at most 2 deadlines are missed. The weakly-hard model is the state-of-the-art for industrial dependability-by-design of control systems that tolerate deterministic failures. Weakly-hard constraints correspond to regular
languages. The size of the minimal finite state machine that recognizes whether a string satisfies the constraint (about 45k states for AnyMiss(2, 300)) is a notorious impediment for the verification of control system properties. This paper discusses an over-approximation of the
language that allows us to provide sound safety guarantees for control systems under deadline misses that would be out of reach using the minimal finite state machine. We present a compressed
language acceptor and prove that it simulates the original finite state machine. We study
language cardinality properties, and report on empirical results that show how the new acceptor can be embedded in the control design workflow, leading to verifying safety for systems for which the state-of-the-art tools do not provide answers.
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Signal Processing
Estimating Target Doppler in Unsynchronized Multistatic ISAC Deployments with Mobile Nodes
Zaman Bhalli, Michele Rossi, Joerg Widmer et al. (+1 more)
Integrated Sensing And Communication (
ISAC) is recognized as a key enabler for future 6th Generation (6G) networks, combining communication capabilities with pervasive sensing. In such systems, the estimation of the Doppler shift plays a crucial role for target characterization. However, typical real-world
ISAC scenarios largely involve bistatic or multistatic configurations and mobile
ISAC nodes. Under these conditions, Doppler estimation becomes particularly challenging, as clock asynchrony between the Transmitter (TX) and the Receivers (RXs), combined with their mobility, introduces additional Doppler components and phase offsets that distort or disrupt the target-induced frequency shift. Existing works have considered these challenges separately or relied on external reference reflectors. In this paper, we present the first method to estimate the Doppler frequency of a target with mobile and asynchronous
ISAC nodes in a multistatic configuration, considering the case of a mobile TX and multiple static RXs, and without leveraging any external reflector. By leveraging the invariance of the phase offsets across multipath components and exploiting geometrical relationships, we show that the problem is solvable if at least 4 RXs are present. We evaluate the proposed solution through numerical simulations in various scenarios, showing that it is a valid approach for estimating target Doppler shifts in unsynchronized multistatic
ISAC deployments with mobile nodes.
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All authors Zaman Bhalli, Michele Rossi, Joerg Widmer, Marco Canil
Signal Processing
Analysis of Fluid Antenna Systems with Continuous Positioning and Spatial Correlation
Gayani Siriwardana, Peter J. Smith, Himal A. Suraweera et al. (+1 more)
We analyze multi-user fluid
antenna systems with continuous positioning over a track of length L under a spatial correlation model, where exact performance distributions become analytically intractable. We develop a level-crossing-rate (LCR) framework that yields asymptotically exact approximations and tight bounds for the cumulative distribution function (cdf) of the optimized metric S* = sup_{0 <= l <= L}, where S(l) denotes the performance metric at
antenna position l. For a single fluid
antenna, we characterize the cdfs of signal-to-noise ratio (SNR), signal-to interference ratio (SIR) and signal-to-interference-plus-noise ratio (SINR) under Rayleigh fading and extend the approach to Ricean desired channels. We further treat two multi-
antenna receiver layouts with maximum-ratio combining: (i) a fluid
antenna with a fixed
antenna and (ii) a two-element moving array, deriving new LCR results for the practically important case where array-element correlation and positional correlation are inherently coupled. The analysis provides actionable insights: high-threshold tail probabilities scale linearly with L, we derive the required L to neutralize a co-channel interferer, and we show that about one wavelength of movement can reduce outage by three orders of magnitude. Monte Carlo results validate the accuracy across the considered scenarios and regimes.
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All authors Gayani Siriwardana, Peter J. Smith, Himal A. Suraweera, Rajitha Senanayake
Signal Processing
Performance Analysis of Movable Antenna Arrays
Gayani Siriwardana, Peter J. Smith, Himal A. Suraweera et al. (+1 more)
This paper provides a thorough mathematical analysis of continuous movable
antenna (MA) arrays. Focusing on the multiple
antenna case, we consider a linear
antenna array with multiple fixed
antenna elements that moves along a line. We assume a full, spatially coherent correlation model and continuous positioning of the array. We provide asymptotically exact approximations to the upper tail of the cumulative distribution function (cdf) of the signal-to-noise ratio (SNR), considering both correlated and uncorrelated
antenna elements in the array. We also obtain a novel closed-form expression for the level crossing rate (LCR) of the SNR under correlated array elements, where a non-separable two-dimensional correlation is present. The analysis is validated through simulations, confirming both the accuracy of the LCR expressions and the tightness of the cdf bounds in the upper tail. Numerical results show that the proposed MA array outperforms single fluid
antenna and fixed array systems, with reduced inter-element spacing providing further performance gains.
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All authors Gayani Siriwardana, Peter J. Smith, Himal A. Suraweera, Rajitha Senanayake
Systems and Control · Cross-listed from cs.RO
Beyond Safety Filtering: Control Barrier Function-Informed Reinforcement Learning for Connected and Automated Vehicles
Jianye Xu and Bassam Alrifaee
Reinforcement Learning (RL) uses rewards to guide learning, yet reward design is typically hand-crafted using heuristics that can be difficult to tune. We propose a Control Barrier Function (CBF)-informed reward design for Multi-
Agent RL (MARL) that converts CBF constraint values under joint MARL actions into a reward signal that explicitly guides safe learning. We compare against two heuristic reward baselines in a four-way multi-lane intersection with connected and automated vehicles. Results show that our method achieves the highest task performance and is less sensitive to reward hyperparameters, yielding consistently strong performance across the tested hyperparameter range. Code for reproducing the experimental results and a
video demonstration are available at https://github.com/bassamlab/SigmaRL.
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