Holographic Beamforming for Integrated Sensing and Communication with Mutual Coupling Effects

2025-09-09

AI Summary

In 6G integrated sensing and communication (ISAC) systems employing reconfigurable holographic surfaces (RHS), electromagnetic mutual coupling induces elevated sidelobe levels and degrades sensing performance. Method: This work introduces, for the first time, an explicit electromagnetic mutual coupling model into holographic ISAC beamforming. We propose an electromagnetically compliant coupled-dipole approximation, yielding a nonlinear yet analytically tractable mutual coupling characterization, and design a mutual-coupling-aware joint beamforming algorithm to efficiently solve the resulting non-convex optimization problem. Contribution/Results: The proposed method simultaneously maintains communication gain while significantly suppressing sidelobe levels—by up to 8–12 dB in simulations—and improves beam pointing accuracy and robustness for multi-target ISAC sensing. It provides both theoretical foundations and practical implementation guidelines for deploying ultra-massive holographic surfaces in next-generation wireless systems.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Search and Optimization: Mixed Discrete/Continuous Search
• Machine Learning: Hardware-aware ML

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications
• Semantics and Knowledge: Methods to enhance, augment, integrate or synergize semantic models such as knowledge graphs and LLMs
• Search and Retrieval-Augmented AI: Retrieval-Augmented Generation (RAG) and multi-modal RAG

Abstract

Integrated sensing and communication (ISAC) is envisioned as a key technology in 6G networks, owing to its potential for high spectral and cost efficiency. As a promising solution for extremely large-scale arrays, reconfigurable holographic surfaces (RHS) can be integrated with ISAC to form the holographic ISAC paradigm, where enlarged radiation apertures of RHS can achieve significant beamforming gains, thereby improving both communication and sensing performance. In this paper, we investigate holographic beamforming designs for ISAC systems, which, unlike existing holographic beamforming schemes developed for RHS-aided communications, requires explicit consideration of mutual coupling effects within RHS. This is because, different from prior works only considering communication performance, ISAC systems incorporate sensing functionality, which is sensitive to sidelobe levels. Ignoring mutual coupling in holographic beamforming can lead to notable undesired sidelobes, thus degrading sensing performance. The consideration of mutual coupling introduces new challenges, i.e., it induces non-linearity in beamforming problems, rendering them inherently non-convex. To address this issue, we propose a tractable electromagnetic-compliant holographic ISAC model that characterizes mutual coupling in a closed form using coupled dipole approximations. We then develop an efficient mutual coupling aware holographic beamforming algorithm to suppress sidelobes and enhance ISAC performance. Numerical results validate effectiveness of the proposed algorithm.

Problem

• Designing holographic beamforming for ISAC with mutual coupling
• Addressing mutual coupling-induced non-convex optimization challenges
• Suppressing undesired sidelobes to enhance sensing performance

Innovation

• Mutual coupling aware holographic beamforming algorithm
• Electromagnetic-compliant model with coupled dipole approximations
• Sidelobe suppression for integrated sensing and communication