Near-Field Integrated Sensing and Communications

TL;DR

This paper introduces a near-field ISAC framework that leverages an additional distance dimension for improved sensing and communication, providing optimal waveform solutions and demonstrating significant performance gains over far-field systems.

Contribution

The paper develops a near-field ISAC framework with new waveform optimization methods and derives the Cramer-Rao bound for joint distance and angle sensing.

Findings

Near-field ISAC outperforms far-field in sensing accuracy.

Optimal waveform solutions are obtained for both digital and hybrid antenna systems.

Numerical results confirm the performance gains of the near-field approach.

Abstract

A near-field integrated sensing and communications (ISAC) framework is proposed, which introduces an additional distance dimension for both sensing and communications compared to the conventional far-field system. In particular, the Cramer-Rao bound for the near-field joint distance and angle sensing is derived, which is minimized subject to the minimum communication rate requirement of each user. Both fully digital antennas and hybrid digital and analog antennas are investigated. For fully digital antennas, a globally optimal solution of the ISAC waveform is obtained via semidefinite relaxation. For hybrid antennas, a high-quality solution is obtained through two-stage optimization. Numerical results demonstrate the performance gain introduced by the additional distance dimension of the near-field ISAC over the far-field ISAC.