Sidelink Positioning: Standardization Advancements, Challenges and Opportunities

TL;DR

This paper reviews recent 3GPP standardization efforts on sidelink positioning, analyzing its capabilities, challenges, and future research directions for precise device-to-device localization in cellular networks.

Contribution

It provides a comprehensive overview of 3GPP Rel-18 standardization progress on sidelink positioning, including architecture, methods, performance, and future challenges.

Findings

Sidelink positioning enhances coverage via direct UE signaling.

Performance varies with spectrum, environment, and methods.

Standardization defines specific accuracy and spectrum requirements.

Abstract

With the integration of cellular networks in vertical industries that demand precise location information, such as vehicle-to-everything (V2X), public safety, and Industrial Internet of Things (IIoT), positioning has become an imperative component for future wireless networks. By exploiting a wider spectrum, multiple antennas and flexible architectures, cellular positioning achieves ever-increasing positioning accuracy. Still, it faces fundamental performance degradation when the distance between user equipment (UE) and the base station (BS) is large or in non-line-of-sight (NLoS) scenarios. To this end, the 3rd generation partnership project (3GPP) Rel-18 proposes to standardize sidelink (SL) positioning, which provides unique opportunities to extend the positioning coverage via direct positioning signaling between UEs. Despite the standardization advancements, the capability of SL positioning is controversial, especially how much spectrum is required to achieve the positioning accuracy defined in 3GPP. To this end, this article summarizes the latest standardization advancements of 3GPP on SL positioning comprehensively, covering a) network architecture; b) positioning types; and c) performance requirements. The capability of SL positioning using various positioning methods under different imperfect factors is evaluated and discussed in-depth. Finally, according to the evolution of SL in 3GPP Rel-19, we discuss the possible research directions and challenges of SL positioning.