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.

翻译：随着蜂窝网络在需要精确位置信息的垂直行业（如车联网、公共安全和工业物联网）中的集成，定位已成为未来无线网络不可或缺的组成部分。通过利用更宽的频谱、多天线和灵活架构，蜂窝定位实现了日益提高的定位精度。然而，当用户设备与基站之间的距离较大或处于非视距场景时，其性能仍面临根本性的下降。为此，第三代合作伙伴计划第18版提议标准化侧链路定位，该技术通过用户设备间的直接定位信令为扩展定位覆盖提供了独特机遇。尽管标准化工作取得进展，侧链路定位的能力仍存在争议，特别是实现3GPP定义的定位精度需要多少频谱资源。为此，本文全面总结了3GPP在侧链路定位方面的最新标准化进展，涵盖：a) 网络架构；b) 定位类型；c) 性能要求。深入评估并讨论了在不同非理想因素下使用多种定位方法的侧链路定位能力。最后，根据3GPP第19版中侧链路的演进方向，我们探讨了侧链路定位可能的研究方向与挑战。