6G Localization and Sensing in the Near Field: Features, Opportunities, and Challenges

TL;DR

This paper explores near-field features in 6G wireless systems, highlighting their potential to enhance localization and sensing capabilities through new hardware enablers like ELAA, RIS, and D-MIMO, and discusses associated opportunities and challenges.

Contribution

It characterizes near-field features in 6G systems and discusses how these features can be leveraged to improve localization and sensing functionalities, outlining future research directions.

Findings

Near-field features include spherical wave model, spatial non-stationarity, and beam squint.

Near-field enables additional geometric information for localization and sensing.

Opportunities and challenges in exploiting near-field features for 6G are discussed.

Abstract

The far-field channel model has historically been used in wireless communications due to the simplicity of mathematical modeling and convenience for algorithm design. 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 (ELAAs), 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 fundamentally built-in functionalities in future wireless systems. Despite appearing in different scenarios and supporting different frequency bands, such enablers share the so-called near-field (NF) features, which will provide extra geometric information conducive to L&S. In this work, we describe the NF features, namely, the spherical wave model, spatial non-stationarity, and beam squint effect. After discussing how L&S see NF differently from communication, the opportunities and open research challenges are provided.