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Wavenumber-domain signal processing for holographic MIMO: Foundations, methods, and future directions

Zijian Zhang, Linglong Dai

TL;DR

By leveraging spatial Fourier plane-wave decomposition to model H-MIMO channels, the wavenumber domain offers a unified and physically consistent basis for characterizing subwavelength-level spatial correlation and spherical wave propagation.

Abstract

Holographic multiple-input multiple-output (H-MIMO) systems represent a paradigm shift in wireless communications by enabling quasi-continuous apertures. Unlike conventional MIMO systems, H-MIMO with subwavelength antenna spacing operates in both far-field and near-field regimes, where classical discrete Fourier transform (DFT) representations fail to sufficiently capture the channel characteristics. To address this challenge, this article provides an overview of the emerging wavenumber-domain signal processing framework. Specifically, by leveraging spatial Fourier plane-wave decomposition to model H-MIMO channels, the wavenumber domain offers a unified and physically consistent basis for characterizing subwavelength-level spatial correlation and spherical wave propagation. This article first introduces the concept of H-MIMO and the wavenumber representation of H-MIMO channels. Next, it elaborates on wavenumber-domain signal processing technologies reported in the literature, including multiplexing, channel estimation, and waveform designs. Finally, it highlights open challenges and outlines future research directions in wavenumber-domain signal processing for next-generation wireless systems.

Wavenumber-domain signal processing for holographic MIMO: Foundations, methods, and future directions

TL;DR

By leveraging spatial Fourier plane-wave decomposition to model H-MIMO channels, the wavenumber domain offers a unified and physically consistent basis for characterizing subwavelength-level spatial correlation and spherical wave propagation.

Abstract

Holographic multiple-input multiple-output (H-MIMO) systems represent a paradigm shift in wireless communications by enabling quasi-continuous apertures. Unlike conventional MIMO systems, H-MIMO with subwavelength antenna spacing operates in both far-field and near-field regimes, where classical discrete Fourier transform (DFT) representations fail to sufficiently capture the channel characteristics. To address this challenge, this article provides an overview of the emerging wavenumber-domain signal processing framework. Specifically, by leveraging spatial Fourier plane-wave decomposition to model H-MIMO channels, the wavenumber domain offers a unified and physically consistent basis for characterizing subwavelength-level spatial correlation and spherical wave propagation. This article first introduces the concept of H-MIMO and the wavenumber representation of H-MIMO channels. Next, it elaborates on wavenumber-domain signal processing technologies reported in the literature, including multiplexing, channel estimation, and waveform designs. Finally, it highlights open challenges and outlines future research directions in wavenumber-domain signal processing for next-generation wireless systems.
Paper Structure (18 sections, 5 figures)

This paper contains 18 sections, 5 figures.

Table of Contents

  1. Introduction
  2. Foundations of Wavenumber-Domain Signal Processing for H-MIMO Systems
  3. Concept of H-MIMO
  4. Wavenumber-Domain H-MIMO Channels
  5. Opportunities in Signal Processing
  6. Wavenumber-Domain Signal Processing
  7. Wavenumber-Division Multiplexing
  8. Wavenumber-Domain Channel Estimation
  9. Wavenumber-Domain Waveform Design
  10. Wavenumber-Domain Integrated Sensing and Communications
  11. Hardware-Constrained Waveform Designs
  12. Open Challenges and Future Directions
  13. Capacity Theory
  14. Tri-Hybrid MIMO Architectures
  15. Mutual Coupling Effects
  16. ...and 3 more sections

Figures (5)

  • Figure 1: An illustration of H-MIMO based transmissions.
  • Figure 2: (a) The channel gains of a 64-antenna MIMO in the spatial domain and the DFT-sampled angular domain. (b) The channel gains of a continuous-aperture H-MIMO in the spatial domain and the wavenumber domain.
  • Figure 3: The trade-off of array gain and multiplexing gain for CAPA and SPDA with different antenna spacing $d$ouyang2025diversity.
  • Figure 4: An illustration of WDM scheme Sanguinetti'23. The source current is composed of three nearly orthogonal basis functions, each carrying one data stream.
  • Figure 5: An illustration of multi-user H-MIMO downlink transmissions Zijian'23'JSAC. The multi-user patterns are designed by PDM scheme for sum-rate maximization. Then, the optimized patterns are deployed on the holographic surface of H-MIMO transmitter to serve multiple receivers.