This article revisits integrated sensing and communication (ISAC) systems that operate in the near-field region of large antenna arrays while utilizing large bandwidths. The article first describes the basic characteristics of a wideband sensing and communication (S&C) channel, highlighting the key changes that occur during the transition from the far-field to the near-field region, namely strong angular delay correlations and non-uniform Doppler frequencies. It is then revealed that the near-field effect can facilitate wideband-like S&C functionality, leading to efficient signal multiplexing and accurate distance sensing, and making large antenna arrays a viable alternative to large bandwidths. In addition, new capabilities for Doppler-domain signal multiplexing and velocity sensing enabled by non-uniform Doppler frequencies, which cannot be achieved by extending the bandwidth alone, are presented. Motivated by these results, several paradigm shifts required to leverage the full potential of near-field wideband ISAC systems are discussed, with particular emphasis on spectrum allocation, antenna array arrangement, transceiver architecture, and waveform design.

翻译：本文重新审视了在大型天线阵列近场区域内运行并利用大带宽的集成感知与通信（ISAC）系统。文章首先描述了宽带感知与通信（S&C）信道的基本特性，重点阐述了从远场到近场区域过渡过程中出现的关键变化，即强角度延迟相关性以及非均匀多普勒频率。随后揭示，近场效应可以增强类宽带感知与通信功能，实现高效的信号复用和精确的距离感知，使大型天线阵列成为大带宽的可行替代方案。此外，还介绍了由非均匀多普勒频率驱动的多普勒域信号复用与速度感知新能力，这些能力仅通过扩展带宽是无法实现的。基于这些发现，本文讨论了充分发挥近场宽带ISAC系统潜力所需的多项范式转变，特别关注频谱分配、天线阵列布局、收发器架构以及波形设计。