Near-Field Challenges in Ultra-Wideband ISAC: Beamforming Strategies and System Insights

TL;DR

This paper addresses near-field challenges in ultra-wideband ISAC systems for 6G, proposing practical beamforming strategies to improve coverage and sensing accuracy amidst near-field effects and beam squint.

Contribution

It introduces novel beamforming codebook designs and validation methods tailored for near-field ultra-wideband ISAC, addressing hardware and system-level challenges.

Findings

Beamforming strategies improve coverage and sensing accuracy.

Simulation results validate the effectiveness of proposed methods.

Trade-offs between communication and sensing performance are analyzed.

Abstract

The shift toward sixth-generation (6G) wireless networks places integrated sensing and communications (ISAC) at the core of future applications such as autonomous driving, extended reality, and smart manufacturing. However, the combination of large antenna arrays and ultra-wide bandwidths brings near-field propagation effects and beam squint to the forefront, fundamentally challenging traditional far-field designs. True time delay units (TTDs) offer a potential solution, but their cost and hardware complexity limit scalability. In this article, we present practical beamforming strategies for near-field ultra-wideband ISAC systems. We explore codebook designs across analog and digital domains that mitigate beam squint, ensure reliable user coverage, and enhance sensing accuracy. We further validate these approaches through large-scale system-level simulations, including 3D map-based evaluations that reflect real-world urban environments. Our results demonstrate how carefully designed beamforming can balance communication throughput with sensing performance, achieving reliable coverage and efficient resource use even under severe near-field conditions. We conclude by highlighting open challenges in hardware, algorithms, and system integration, pointing toward research directions that will shape the deployment of 6G-ready ISAC networks.