Réunion

Coordination and Security Constraints in ISAC systems, Michèle Wigger (L2S, CentraleSupelec)

This talk takes an information-theoretic perspective on integrated sensing and communication (ISAC) systems, with a focus on coordination, sensing, and security. Coordination refers to the requirement that the transmitter, the receiver, or an external eavesdropper generate (or, in the case of the eavesdropper, fail to generate) actions that follow a given target statistical behavior with a source or state sequence. In particular, part of our work studies settings where both the communicated message and the state information must remain secret from an external eavesdropper We present new coding schemes, simple estimation schemes, and fundamental limits that characterize the trade-offs between communication, sensing, coordination, shared randomness, and secrecy.

Goal-oriented Resource Allocation for Collaborative Integrated Sensing and Communication, Trong-duy Tran (CentraleSupelec)

We consider resource allocation for a collaborative integrated sensing and communication (ISAC) scenario, in which distributed smart devices can be scheduled to perform sensing and transmit their sensing features to a fusion center. The fusion center aims to perform classification tasks on the environment based on received features. A scalable network sensing framework is proposed to balance the performance of the sensing service with that of the classical enhanced Mobile Broadband (eMBB) service. We adopt a tractable theoretical metric, the discriminant gain, as a proxy for the classification goal. We formulate cross-layer optimization problems to maximize discriminant gain under constraints on energy consumption and eMBB communication quality for the independent and joint scheduling policies. The joint scheduling policy has considerably higher complexity than the independent scheduling policy, in exchange for better collaborative sensing performance. A simplified gain model is proposed to reduce the complexity and practicality of the joint scheduling policy. Both policies are obtained via successive convex approximation and parametric convex optimization. Extensive experiments are conducted to verify the goal-oriented framework and the two policies. It is demonstrated that the two policies outperform the baseline policies with both synthetic and realistic radar simulation datasets. The joint scheduling policy can exploit device correlations and thus performs better than the independent scheduling policy under strong correlations and strict communication constraints.

LMMSE-Based Phase Estimator for Fiber-Optic Coherent Spread-Spectrum DAS systems, Yiyang Bai (Telecom Paris)

Fiber-optic distributed acoustic sensing (DAS) enables long-distance environmental monitoring by tracking the phase changes between the transmitted and reflected light waves along a fiber. A major source of disturbance in such systems is laser phase noise, and its influence is typically mitigated by means of additional hardware. In this article, we propose to mitigate the influence of laser phase noise by means of digital signal processing. We propose a practical estimator for coherent single-polarization spread-spectrum DAS system, which is motivated by linearizing both the complex DAS model as well as the minimum-mean square (MMSE)-type loss-function. Moreover, a Cramér-Rao type lower bound is presented. Our simulation results  demonstrate that the performance of our proposed estimator lies close to the lower bound, thus indicating that it effectively compensates for the phase noise in the DAS sensing system.

Low Complexity V2V Communication using ISAC FMCW Radar under Clock Impairments, Guillaume Metaut (ETIS, ENSEA)

Integrated Sensing and Communication (ISAC) has gain significant popularity in the academia over the recent years as it could significantly contribute to the improvements of future digital communication systems capabilities. One of the key areas where ISAC could be implemented is in embedded radar system for transportation. We propose to investigate the communication potential of Frequency Modulated Continuous Wave (FMCW) radar in a context of clock impairments in the radar hardware. We first present a low-complexity transceiver architecture that utilizes phase modulation of FMCW signals to achieve reliable communication. Then we establish a comprehensive model for clock impairments affecting both the ramp generator and the Analog-to-Digital Converter (ADC) sampling clock. Furthermore, a theoretical Signal-to-Noise Ratio (SNR) framework for the ISAC radar is derived. Through extensive simulations, we evaluate communication performance in terms of Bit Error Rate (BER) across varying clock specifications. Our findings demonstrate that selecting an optimal receive filter can effectively mitigate distortions induced by clock impairments.

Analytical PSLR and ISLR Expressions for OTFS Radar Performance Evaluation, Sirine Hamrouni (IETR, INSA Rennes)

Orthogonal time-frequency space (OTFS) modulation is a promising waveform for high-mobility radar sensing in joint radar-communication scenarios. Yet, its performance is still primarily assessed through simulations. This paper presents a rigorous analytical characterization of OTFS radar in the delay-Doppler domain. Simple and accurate closed-form expressions are derived for the matched-filter output statistics, including the mean, average energy, main-lobe energy, and sidelobe metrics such as the peak sidelobe level ratio (PSLR) and integrated sidelobe level ratio (ISLR). Based on these expressions, the performance is analyzed by examining how these metrics evolve with delay and Doppler. The theoretical expressions are validated using end-to-end OTFS radar simulations. This analytical framework provides the tools and foundation for further waveform design and optimization.

Trade-offs and Non-idealities in ISAC Systems: Embracing Impairments for Sensing, Musa Furkan Keskin (Senior Researcher, Chalmers University of Technology, Sweeden)

Integrated sensing and communication (ISAC) has emerged as a cornerstone technology for 6G, enabling simultaneous data exchange and environmental sensing through shared spectrum and hardware. This talk begins with an overview of OFDM-based monostatic ISAC systems and highlights two fundamental trade-offs in time-frequency domain, arising from the choice of data constellation and power allocation. We then discuss key differences between sensing and communication in the presence of non-idealities, with particular emphasis on phase noise (PN), inter-carrier interference (ICI) and inter-symbol interference (ISI). Building on the observation that such impairments in monostatic ISAC induce distinct signatures that convey valuable information about the geometric properties of targets (such as range and velocity), we propose a fundamental rethinking of their role from foe to friend. Rather than treating impairments solely as nuisances to be mitigated, we demonstrate how they can be exploited to enhance monostatic sensing performance, potentially surpassing even that of ideal, impairment-free systems, in stark contrast to their purely detrimental nature in communications.

Contrôle statistique de l'énergie pour le sensing data-aided off-grid en OTFS-QAM, Lina Mroueh (ISEP)

Ce travail propose une méthode d'ISAC orientée communication pour des systèmes OTFS-QAM. Le sensing est réalisé à partir de patches dispersés dans le plan temps-fréquence, exploités après décodage des données. Une référence PSK à énergie constante fournit un noyau de sensing déterministe, tandis que la QAM améliore l'efficacité spectrale mais introduit des fluctuations d'énergie qui peuvent dégrader la détection. La méthode proposée combine une optimisation hors ligne de la géométrie du patch avec une mise en forme probabiliste conjointe des symboles QAM. Cette mise en forme contrôle les fluctuations d'énergie, préserve un noyau moyen de type PSK et réduit les perturbations hors centre susceptibles de masquer des cibles faibles. Le travail étudie aussi la localisation off-grid de cibles faibles en présence d'une cible forte. Après détection, un raffinement cohérent permet d'estimer la position continue de la cible dans le plan délai-Doppler. Une analyse de Cramér-Rao sert de référence post-détection pour relier la précision atteignable à la géométrie locale du noyau de sensing. Les résultats montrent une amélioration de la détection de cibles faibles par rapport aux approches symbole par symbole, ainsi qu'une précision off-grid proche de la borne de Cramér-Rao après correction du biais. Le schéma obtenu offre ainsi des compromis favorables entre sensing et communication en 16QAM et 64QAM.

Distributed ISAC Evaluation based on Channel Measurements in Indoor Premises with Human Body Presence, Raffaele D’Errico (CEA)

In this talk, we introduce a channel sounding campaign conducted to assess the feasibility of radio-based sensing in Distributed Integrated Sensing And Communication (ISAC) contexts. The channel measurements are combined to consider monostatic and multi-static scenarios, to illustrate benefits from spatially distributed multi-node sensing approaches in terms of diversity and measurement redundancy. 

An Experimental Assessment of Reconfigurable Intelligent Surfaces Frequency Selectivity, Cyrille Morin (INRIA)

In this work we aim to explore what the actual drawbacks of a RIS deployment in a system with coexisting communication systems are, studying its effects on co- and adjacent channel communications. To that end, we provide actual radio measurements gathered in the SLICES/CorteXlab testbed, featuring a functioning RIS device in the FR1 sub-6GHz band. We show that a RIS device can have a far reaching impact on unsuspecting communication systems, in terms of path loss, but also on equalization performance when switching state.

Carrier-Phase Localization and Sensing in Phase-Coherent Distributed Antenna Systems, Gonzalo Seco-Granados (Universitat Autonoma of Barcelona, Spain)

Accurate localization and sensing are key enablers for future 5G and 6G networks, supporting applications in intelligent transportation, logistics, monitoring, and autonomous systems. While carrier-phase measurements are the foundation of high-precision GNSS, their integration into wireless networks remains an open challenge due to the inherent ambiguity resolution problem. The talk first reviews the principles of carrier-phase positioning and highlights the unique threshold behavior arising from the mixed real–integer nature of the estimation problem. A novel mixed real–integer performance bound is presented, capable of accurately predicting positioning performance across both successful and unsuccessful ambiguity-resolution regimes, overcoming the limitations of classical Cramér–Rao bounds. The presentation then explores carrier-phase positioning in phase-coherent distributed antenna systems and cell-free massive MIMO deployments, where large distributed apertures enable the exploitation of near-field wavefront curvature for joint localization, synchronization, and environmental mapping. Key enablers and open research challenges are examined, including multi-epoch processing, mobility, cycle slips, multi-band carrier-phase measurements, low-complexity initialization methods, use in non-terrestrial networks, and the effect of multipath. The results indicate that 5G and 6G networks can provide highly favorable conditions for carrier-phase positioning, potentially enabling centimeter-level localization performance beyond what is achievable with conventional delay-based methods.

Hierarchical RIS Orchestration and Dynamic Link-Level Resource Allocation for Shadowing-Based Detection under Sensing-Communication QoS Trade-off, Tan-Tho Luc (CEA-Leti)

This contribution investigates a hierarchical optimisation framework for RIS-assisted distributed ISAC systems relying on radio environment scanning and passive shadowing-based detection. Building upon prior work on dual-beam RIS sensing and sequential ISAC protocols, it addresses the joint sensing/communication trade-off through adaptive link-level resource allocation and network-level RIS orchestration. A greedy k-coverage-inspired RIS selection strategy is combined with dynamic allocation of sensing duration and scanning resources to maximise DL communication QoS while guaranteeing minimum global sensing coverage and field-of-view requirements. The proposed framework considers multi-BS/multi-UE deployments where RIS-associated UEs serving as sensing receivers alternate between sensing and communication phases under SINR- and capacity-driven constraints.

Localization via Delay-Doppler-Angle Domain Channel State Information, Anil Kumar (Inria)

In modern communication frameworks such as Orthogonal Time Frequency Space (OTFS), Delay-Doppler (DD) domain Channel State Information (CSI) is estimated inherently. Furthermore, Delay, Doppler and Angle (DDA) CSI can be extracted from existing 5G signals using super-resolution techniques. While cellular localization is an active research area, existing methods frequently rely on processing measurements across multiple base stations. This work explores the feasibility of performing user localization using DDA domain CSI at a single base station. Using a relatively simpler setup, we demonstrate that localization is achievable provided that parameters such as Time Difference of Arrival (TDoA), Doppler shift, and Angle of Arrival (AoA) are estimated for a sufficient number of multipath components. We then extend these techniques to realistic environments and discuss the resulting implications, including privacy concerns. Finally, we highlight potential applications, such as Simultaneous Localization and Mapping (SLAM), supported by this methodology.

Pilot Design for Bistatic OFDM ISAC, Ayla Moubayed (Orange Labs)

The presentation focuses on Integrated Sensing and Communication (ISAC), a promising direction for future 6G wireless systems where communication and sensing functionalities are combined within the same framework. In particular, the work investigates OFDM-based ISAC systems using 5G NR reference signals, with an emphasis on Positioning Reference Signals (PRS) due to their favorable sensing characteristics. A key challenge addressed in this work is the comb structure of PRS in the time-frequency grid, which introduces empty resource elements and leads to ghost targets in range-Doppler estimation. These false detections can significantly affect sensing reliability in practical bistatic OFDM ISAC scenarios. The presentation discusses how pilot design impacts sensing performance and explores channel estimation strategies aimed at mitigating these artifacts.