The far-field channel model has historically been used in wireless communications due to the simplicity of mathematical modeling and convenience for algorithm design, and its validity for relatively small array apertures. With the need for high data rates, low latency, and ubiquitous connectivity in the sixth generation (6G) of communication systems, new technology enablers such as extremely large antenna arrays (ELAA), reconfigurable intelligent surfaces (RISs), and distributed multiple-input-multiple-output (D-MIMO) systems will be adopted. These enablers not only aim to improve communication services but also have an impact on localization and sensing (L\&S), which are expected to be integrated into future wireless systems. Despite appearing in different scenarios and supporting different frequency bands, these enablers share the so-called near-field (NF) features, which will provide extra geometric information. In this work, starting from a brief description of NF channel features, we highlight the opportunities and challenges for 6G NF L\&S.

翻译：由于远场信道模型在数学建模上的简易性、算法设计的便利性以及对于较小阵列孔径的有效性，该模型历来被用于无线通信。随着第六代（6G）通信系统对高数据速率、低时延和泛在连接的需求，诸如超大规模天线阵列（ELAA）、可重构智能表面（RIS）和分布式多输入多输出（D-MIMO）系统等新型技术赋能手段将被采用。这些赋能手段不仅旨在提升通信服务，还将对将集成到未来无线系统中的定位与感知功能产生影响。尽管它们出现在不同场景并支持不同频段，但这些赋能手段共享所谓的近场特性，这将提供额外的几何信息。本文从简要描述近场信道特性出发，重点阐述了6G近场定位与感知的机遇与挑战。