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Unlocking Potentials of Near-Field Propagation: ELAA-Empowered Integrated Sensing and Communication

Zhenyao He, Wei Xu, Zhaohui Yang, Hong Shen, Ningning Fu, Yongming Huang, Zhaoyang Zhang, Xiaohu You

TL;DR

This work addresses the challenge of enabling integrated sensing and communication (ISAC) in the near-field regime enabled by extremely large antenna arrays (ELAAs) at high frequencies. It analyzes fundamental near-field propagation with spherical-wavefronts, identifies additional distance DoFs, and examines their impact on communication, sensing, and the ISAC paradigm. The paper proposes sensing-aided beam training and beam squint-enhanced sensing, outlines enabling techniques such as RIS-based near-field region construction and full-duplex ISAC, and discusses applications including integrated localization, interference management, security, and multi-station collaboration, supported by a case study. The findings highlight the opportunities and challenges of ELAA-empowered near-field ISAC, offering a roadmap for theories, hardware, and transmission designs needed to realize practical systems and improved localization and sensing performance in 6G and beyond.

Abstract

The exploration of extremely large antenna arrays (ELAAs) using high-frequency spectrum has led to a paradigm shift in electromagnetic radiation field, transitioning from the common use case of far-field propagation to near-field propagation. This shift necessitates the modification of the conventional planar-wavefront approximation to more accurate spherical waves, exerting a profound impact on wireless transmission technologies encompassing communication and sensing. Concurrently, integrated sensing and communication (ISAC) has gained prominence in the context of the sixth-generation (6G) wireless networks owing to its ability to cater to the ever-increasing demands of future networks. In line with this evolving trend, this article presents a systematical investigation on ELAA-empowered near-field ISAC. We begin by introducing the fundamentals of near-field propagation with an emphasis on its double-edged effects to near-field communications. Then, we turn to near-field sensing and expound upon various typical applications. Following the separate elaborations on communications and sensing, we articulate in-depth advantages of ELAA-empowered ISAC in near field, particularly including featured opportunities arising from the dual-functional integrations, potential ISAC applications benefiting from the additional degrees-of-freedom in near field, and enablements of other complementary technologies. Finally, we outline key technical challenges that merit further exploration in the realm of ELAA-empowered near-field ISAC.

Unlocking Potentials of Near-Field Propagation: ELAA-Empowered Integrated Sensing and Communication

TL;DR

This work addresses the challenge of enabling integrated sensing and communication (ISAC) in the near-field regime enabled by extremely large antenna arrays (ELAAs) at high frequencies. It analyzes fundamental near-field propagation with spherical-wavefronts, identifies additional distance DoFs, and examines their impact on communication, sensing, and the ISAC paradigm. The paper proposes sensing-aided beam training and beam squint-enhanced sensing, outlines enabling techniques such as RIS-based near-field region construction and full-duplex ISAC, and discusses applications including integrated localization, interference management, security, and multi-station collaboration, supported by a case study. The findings highlight the opportunities and challenges of ELAA-empowered near-field ISAC, offering a roadmap for theories, hardware, and transmission designs needed to realize practical systems and improved localization and sensing performance in 6G and beyond.

Abstract

The exploration of extremely large antenna arrays (ELAAs) using high-frequency spectrum has led to a paradigm shift in electromagnetic radiation field, transitioning from the common use case of far-field propagation to near-field propagation. This shift necessitates the modification of the conventional planar-wavefront approximation to more accurate spherical waves, exerting a profound impact on wireless transmission technologies encompassing communication and sensing. Concurrently, integrated sensing and communication (ISAC) has gained prominence in the context of the sixth-generation (6G) wireless networks owing to its ability to cater to the ever-increasing demands of future networks. In line with this evolving trend, this article presents a systematical investigation on ELAA-empowered near-field ISAC. We begin by introducing the fundamentals of near-field propagation with an emphasis on its double-edged effects to near-field communications. Then, we turn to near-field sensing and expound upon various typical applications. Following the separate elaborations on communications and sensing, we articulate in-depth advantages of ELAA-empowered ISAC in near field, particularly including featured opportunities arising from the dual-functional integrations, potential ISAC applications benefiting from the additional degrees-of-freedom in near field, and enablements of other complementary technologies. Finally, we outline key technical challenges that merit further exploration in the realm of ELAA-empowered near-field ISAC.
Paper Structure (27 sections, 4 figures, 1 table)

This paper contains 27 sections, 4 figures, 1 table.

Table of Contents

  1. Introduction
  2. Near-Field Propagation and Communications
  3. Fundamentals of Near-Field Propagation
  4. Wireless Communications in Near-Field Regions
  5. Potentials
  6. Challenges
  7. Wireless Sensing in Near-Field Regions
  8. Near-Field Radio Frequency Imaging
  9. Near-Field Localization based on Spherical Wavefront
  10. Parameter Estimations of Near-Field Channels
  11. ELAA-Empowered Near-Field ISAC
  12. Solution and New Viewpoint for Near-Field ISAC
  13. Sensing-Aided Near-Field Beam Training
  14. Near-Field Beam Squint-Enhanced Sensing
  15. Benefits and Potential Applications of Near-field ISAC
  16. ...and 12 more sections

Figures (4)

  • Figure 1: ISAC-empowered near-field transmission scheme: near-field beam squint-enhanced sensing and sensing-aided near-field beam training.
  • Figure 2: An illustration of near-field ISAC network and four representative potential applications: integrated localization and communication, interference management, physical-layer security enhancement, and near-field multi-station collaborative ISAC.
  • Figure 3: RIS-enabled near-field ISAC: active near-field region construction via deploying ELAA RIS and the impact of non-ideal reflection elements in RIS.
  • Figure 4: Computer experimental examples of an ELAA-empowered near-field ISAC system: a) beampattern of near-field ISAC; b) performance of near-field ISAC, where $\text{RCRB}_{\rm a}$ and $\text{RCRB}_{\rm d}$ represent the RCRBs for angle and distance estimations, respectively.