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：远场信道模型由于数学建模简单、算法设计便利，且适用于相对较小的天线孔径，历史上一直被用于无线通信。随着第六代（6G）通信系统对高数据速率、低延迟和泛在连接的需求，诸如超大规模天线阵列（ELAA）、可重构智能表面（RISs）和分布式多输入多输出（D-MIMO）系统等新技术使能器将被采用。这些使能器不仅旨在改善通信服务，还对未来无线系统将集成的定位与感知（L&S）功能产生影响。尽管这些使能器出现在不同场景并支持不同频段，但它们共享所谓的近场（NF）特征，这将提供额外的几何信息。本文从简要描述近场信道特征出发，重点阐述了6G近场定位与感知的机遇与挑战。