Enhancing Near-Field Sensing and Communications with Sparse Arrays: Potentials, Challenges, and Emerging Trends

TL;DR

This paper explores the use of sparse large-scale antenna arrays with spherical-wave modeling to enhance near-field sensing and communications in 6G systems, addressing hardware, algorithm challenges, and emerging applications.

Contribution

It introduces the concept of XL-sparse arrays with multi-subarray designs for mmWave/THz systems, advancing near-field sensing and communication capabilities.

Findings

Sparse arrays improve spatial resolution and degrees of freedom.

Spherical-wave modeling enhances near-field sensing accuracy.

XL-sparse arrays enable promising 6G applications.

Abstract

As a promising technique, extremely large-scale (XL)-arrays offer potential solutions for overcoming the severe path loss in millimeter-wave (mmWave) and TeraHertz (THz) channels, crucial for enabling 6G. Nevertheless, XL-arrays introduce deviations in electromagnetic propagation compared to traditional arrays, fundamentally challenging the assumption with the planar-wave model. Instead, it ushers in the spherical-wave (SW) model to accurately represent the near-field propagation characteristics, significantly increasing signal processing complexity. Fortunately, the SW model shows remarkable benefits on sensing and communications (S\&C), e.g., improving communication multiplexing capability, spatial resolution, and degrees of freedom. In this context, this article first overviews hardware/algorithm challenges, fundamental potentials, promising applications of near-field S\&C enabled by XL-arrays. To overcome the limitations of existing XL-arrays with dense uniform array layouts and improve S\&C applications, we introduce sparse arrays (SAs). Exploring their potential, we propose XL-SAs for mmWave/THz systems using multi-subarray designs. Finally, several applications, challenges and resarch directions are identified.