Holographic Intelligence Surface Assisted Integrated Sensing and Communication

Traditional discrete-array-based systems fail to exploit interactions between closely spaced antennas, resulting in inadequate utilization of the aperture resource. In this paper, we propose a holographic intelligence surface (HIS) assisted integrated sensing and communication (HISAC) system, wherein both the transmitter and receiver are fabricated using a continuous-aperture array. A continuous-discrete transformation of the HIS pattern based on the Fourier transform is proposed, converting the continuous pattern design into a discrete beamforming design. We formulate a joint transmit-receive beamforming optimization problem for the HISAC system, aiming to balance the performance of multi-target sensing while fulfilling the performance requirement of multi-user communication. To solve the non-convex problem with coupled variables, an alternating optimization-based algorithm is proposed to optimize the HISAC transmit-receive beamforming in an alternate manner. Specifically, the transmit beamforming design is solved by decoupling into a series of feasibility-checking sub-problems while the receive beamforming is determined by the Rayleigh quotient-based method. Simulation results demonstrate the superiority of the proposed HISAC system over traditional discrete-array-based ISAC systems, achieving significantly higher sensing performance while guaranteeing predetermined communication performance.

💡 Research Summary

The paper introduces a novel integrated sensing and communication (ISAC) framework that leverages holographic intelligence surfaces (HIS) with continuous apertures at both the transmitter and receiver. Traditional discrete antenna arrays, constrained by half‑wavelength spacing, cannot fully exploit the physical aperture and suffer from mutual coupling modeling inaccuracies. By contrast, a HIS can be regarded as a quasi‑continuous aperture formed by densely packed sub‑wavelength tunable elements, enabling near‑aperture‑limited directivity and higher array gain for the same physical size.

To make the infinite‑dimensional surface current design tractable, the authors develop a continuous‑to‑discrete transformation based on a Fourier series expansion. The continuous current distribution (j(\mathbf{p})) on the surface is expressed as a finite set of wave‑number (wavenumber) coefficients, which are interpreted as transmit and receive beamforming matrices in the wavenumber domain. This mapping yields an equivalent steering‑vector representation that aligns the HIS model with conventional discrete‑array beamforming formulations, allowing the reuse of well‑established optimization tools.

The system model considers (K) single‑antenna communication users and (M) radar targets. The transmitted signal vector (\mathbf{x}=