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Cross Far- and Near-Field Beam Management Technologies in Millimeter-Wave and Terahertz MIMO Systems

Yuhang Chen, Heyin Shen, Chong Han

TL;DR

This survey addresses BM for mmWave/THz MIMO systems operating across FF, NF, and CF regimes, where the Rayleigh distance and cross-field transitions become crucial. It analyzes field-aware channel models—SWM for NF, PWM for FF, and HSPM as a hybrid—to illustrate how angular and distance resolutions shape beam patterns and BM design. The authors categorize BM techniques into searching-based, ML-based, and side-information-assisted approaches, and discuss open challenges, including extending FF methods to NF/CF, designing unified field-agnostic BM, and achieving low-overhead BM in dynamic environments. The work provides a comprehensive blueprint for developing unified, efficient BM strategies that maintain reliable high-frequency links as networks evolve toward 6G and beyond, with practical implications for codebook design, beam training, channel estimation, and tracking. The emphasis on field-aware modeling and cross-field coherence underpins practical BM design for NF/CF THz/mmWave systems, guiding future research toward robust, scalable, and low-complexity solutions.

Abstract

The evolution of wireless communication toward next-generation networks introduces unprecedented demands on data rates, latency, and connectivity. To meet these requirements, two key trends have emerged: the use of higher communication frequencies to provide broader bandwidth, and the deployment of massive multiple-input multiple-output systems with large antenna arrays to compensate for propagation losses and enhance spatial multiplexing. These advancements significantly extend the Rayleigh distance, enabling near-field (NF) propagation alongside the traditional far-field (FF) regime. As user communication distances dynamically span both FF and NF regions, cross-field (CF) communication has also emerged as a practical consideration. Beam management (BM)-including beam scanning, channel state information estimation, beamforming, and beam tracking-plays a central role in maintaining reliable directional communications. While most existing BM techniques are developed for FF channels, recent works begin to address the unique characteristics of NF and CF regimes. This survey presents a comprehensive review of BM techniques from the perspective of propagation fields. We begin by building the basic through analyzing the modeling of FF, NF, and CF channels, along with the associated beam patterns for alignment. Then, we categorize BM techniques by methodologies, and discuss their operational differences across propagation regimes, highlighting how field-dependent channel characteristics influence design tradeoffs and implementation complexity. In addition, for each BM method, we identify open challenges and future research directions, including extending FF methods to NF or CF scenarios, developing unified BM strategies for field-agnostic deployment, and designing low-overhead BM solutions for dynamic environments.

Cross Far- and Near-Field Beam Management Technologies in Millimeter-Wave and Terahertz MIMO Systems

TL;DR

This survey addresses BM for mmWave/THz MIMO systems operating across FF, NF, and CF regimes, where the Rayleigh distance and cross-field transitions become crucial. It analyzes field-aware channel models—SWM for NF, PWM for FF, and HSPM as a hybrid—to illustrate how angular and distance resolutions shape beam patterns and BM design. The authors categorize BM techniques into searching-based, ML-based, and side-information-assisted approaches, and discuss open challenges, including extending FF methods to NF/CF, designing unified field-agnostic BM, and achieving low-overhead BM in dynamic environments. The work provides a comprehensive blueprint for developing unified, efficient BM strategies that maintain reliable high-frequency links as networks evolve toward 6G and beyond, with practical implications for codebook design, beam training, channel estimation, and tracking. The emphasis on field-aware modeling and cross-field coherence underpins practical BM design for NF/CF THz/mmWave systems, guiding future research toward robust, scalable, and low-complexity solutions.

Abstract

The evolution of wireless communication toward next-generation networks introduces unprecedented demands on data rates, latency, and connectivity. To meet these requirements, two key trends have emerged: the use of higher communication frequencies to provide broader bandwidth, and the deployment of massive multiple-input multiple-output systems with large antenna arrays to compensate for propagation losses and enhance spatial multiplexing. These advancements significantly extend the Rayleigh distance, enabling near-field (NF) propagation alongside the traditional far-field (FF) regime. As user communication distances dynamically span both FF and NF regions, cross-field (CF) communication has also emerged as a practical consideration. Beam management (BM)-including beam scanning, channel state information estimation, beamforming, and beam tracking-plays a central role in maintaining reliable directional communications. While most existing BM techniques are developed for FF channels, recent works begin to address the unique characteristics of NF and CF regimes. This survey presents a comprehensive review of BM techniques from the perspective of propagation fields. We begin by building the basic through analyzing the modeling of FF, NF, and CF channels, along with the associated beam patterns for alignment. Then, we categorize BM techniques by methodologies, and discuss their operational differences across propagation regimes, highlighting how field-dependent channel characteristics influence design tradeoffs and implementation complexity. In addition, for each BM method, we identify open challenges and future research directions, including extending FF methods to NF or CF scenarios, developing unified BM strategies for field-agnostic deployment, and designing low-overhead BM solutions for dynamic environments.

Paper Structure

This paper contains 59 sections, 38 equations, 12 figures, 5 tables.

Table of Contents

  1. INTRODUCTION
  2. Far-field, Near-field and Cross-field Communications
  3. Beam Management
  4. Beam Scanning
  5. CSI Estimation
  6. Beamforming
  7. Beam Tracking
  8. Motivations and Contributions
  9. BASIC OF FIELD-AWARE BM
  10. Far-Field, Near-Field and Cross-Field Channels
  11. Spherical-Wave Channel Model
  12. Planar-Wave Channel Model
  13. Hybrid-Spherical and Planar-Wave Channel Model
  14. Channel Analysis
  15. Accuracy and Applicability of the PWM
  16. ...and 44 more sections

Figures (12)

  • Figure 1: Illustration of users in different propagation regions.
  • Figure 2: Illustration of two representative beam management procedures: (a) beam estimation followed by beam alignment, and (b) channel estimation followed by beamforming.
  • Figure 3: Organization of this paper
  • Figure 4: Channel model in 2D planar array systems.
  • Figure 5: Errors of PWM and HSPM versus communication distance.
  • ...and 7 more figures