“From Monostatic to Distributed ISAC in 6G: Trade-Offs and Non-Idealities in Sensing and Imaging”
Date, hour and room to be defined
Speaker:
- Henk Wymeersch (Chalmers Univ. of Technology , SE)
Motivation and Context
Integrated sensing and communication (ISAC) is expected to play a central role in 6G by enabling joint connectivity and environmental awareness through shared spectrum, hardware and waveform. This tutorial will provide an evolutionary overview of state-of-the-art ISAC across its main architectural paradigms.
First, we cover monostatic ISAC, where the sensing receiver is co-located with the ISAC transmitter. We highlight representative use cases, core signal processing blocks for detection/estimation and the distinctive role of non-idealities/hardware impairments (e.g., phase noise) that can be mitigated and even exploited to enhance sensing.
Second, we examine the transition to distributed ISAC (D-ISAC), where spatially separated nodes enable bistatic and multistatic sensing. While D-ISAC offers major gains in spatial diversity, coverage and sensing performance, it also introduces fundamental challenges in synchronization, calibration and resource management across distributed nodes. For both monostatic ISAC and multistatic D-ISAC, we discuss four fundamental aspects: (i) theoretical foundations, (ii) communication-sensing integration strategies, waveform design approaches and signal processing methods; (iii) trade-offs in time, frequency and space; (iv) non-idealities, such as phase noise, inter-carrier interference and synchronization errors.
In both monostatic ISAC and D-ISAC, we distinguish between two sensing paradigms: target localization (estimation of target state) and imaging (2D/3D environment mapping). In particular, this tutorial offers a solid understanding of the fundamentals of multistatic coherent imaging for D-ISAC, which represents the ultimate sensing paradigm in the path toward 6G.
Offering both foundational knowledge for newcomers and advanced insights for experienced researchers and industry practitioners engaged in 6G development, this tutorial provides a unified perspective on key ISAC paradigms underpinning future wireless systems and thus elaborates on topics that are both timely and interesting for the attendees of EuCNC & 6G Summit.
Structure and Content
This tutorial contains three parts, namely: (i) Fundamentals of monostatic ISAC, (ii) Principles and architectures of D-ISAC, and (iii) Fundamentals, signal processing and key advances in DISAC imaging. The tentative presenters and the outline of each section are summarized as follows:
Part 1: Monostatic ISAC: fundamentals, trade-offs and non- idealities (Presenter: Musa Furkan Keskin, Approx. 1 Hour)
This part focuses on the fundamentals of monostatic ISAC systems. We discuss key trade-offs and non-idealities impacting sensing and communication performance, and elaborate on optimization and signal processing techniques to manage them, along with mitigation and exploitation approaches.
The covered contents are as follows:
- Monostatic Sensing Systems: Introduce observation models and investigate key degrees-of-freedom affecting both sensing and communication functionalities
- Transmit Optimization for Monostatic ISAC: Present optimization techniques for sensing-optimal waveform design targeting delay-Doppler ambiguity shaping and ISAC design aiming to maximize rate under radar proximity constraints
- Receiver Design for Monostatic Sensing: Discuss monostatic sensing receivers and characterize their range-Doppler side-lobe performance
- Trade-offs in Monostatic ISAC: Discuss time-frequency trade-offs (modulation order and subcarrier powers), and spatial trade-offs (ISAC beamformers), along with their impacts on target detection and achievable rate
- Non-idealities in Monostatic ISAC: Explore interference and phase noise in monostatic sensing, focusing on how their manifestation differs from communications, alongside mitigation and exploitation techniques.
Part 2: Fundamentals of D-ISAC operations and systems (Presenter: Henk Wymeersch, Approx. 1 Hour)
This part introduces the fundamental concepts underlying D-ISAC. We outline the motivation for distributed operation, highlight representative 6G use cases such as autonomous driving, public safety, and infrastructure monitoring, and discuss the corresponding key performance metrics. This part further contrasts monostatic and bistatic ISAC systems, and examines the additional opportunities and challenges introduced by multistatic D-ISAC networks.
The specific topics covered are:
- Why Distributed Systems: Address the limitations of standalone systems and outline the motivation for integrating sensing and communication within a distributed framework
- Bistatic vs. Monostatic vs Multistatoc ISAC: Explain major distinctions between monostatic and bistatic configurations and discuss data-aided sensing in bistatic ISAC. Explore opportunities for phase-coherent multistatic sensing and localization along with associated challenges (resource manage-ment for node coordination, synchronization)
- Trade-offs in D-ISAC: Discuss time-frequency-space and node mode selection trade-offs in communication and sensing
- Non-idealities in D-ISAC: explore interference models and synchronization challenges in D-ISAC, as well as potential solutions
Part 3: D-ISAC imaging: undamental theory, KPIs, methods and trade-offs (Presenter: Dario Tagliaferri, Approx. 1 Hour)
This section delves into ISAC imaging systems. We outline the fundamental differences between target localization and radio imaging, in terms of fundamental theories and KPIs, building a solid background for the development of signal processing techniques for image synthesis and environment reconstruction. Then, we delve into the integration of multistatic coherent imaging functionalities in D-MIMO systems, outlining design principles and important performance trade-offs.
The detailed contents are as follows:
- Why Imaging: differences between imaging and target localization, use cases in 6G (autonomous driving, public safety, environment and weather monitoring, and others)
- Imaging Fundamentals and KPIs: diffraction tomography theory and spatial ambiguity function, theoretical vs. effective resolution, image entropy
- Coherent vs. Incoherent Imaging: differences, advantages, disadvantages of both approaches, requirements (multistatic time-frequency-phase synchronization) and challenges (spatial and frequency anisotropy of extended targets)
- Signal processing for Multistatic Image Formation: matched filter (MF) approach (backprojection), hints on reconstruction by regularized inversion
- Trade-offs: waveform design, options for spatial precoding design, performance trade-offs and key insights
