Efficient localization plays a vital role in many modern applications of Unmanned Ground Vehicles (UGV) and Unmanned aerial vehicles (UAVs), which would contribute to improved control, safety, power economy, etc. The ubiquitous 5G NR (New Radio) cellular network will provide new opportunities for enhancing localization of UAVs and UGVs. In this paper, we review the radio frequency (RF) based approaches for localization. We review the RF features that can be utilized for localization and investigate the current methods suitable for Unmanned vehicles under two general categories: range-based and fingerprinting. The existing state-of-the-art literature on RF-based localization for both UAVs and UGVs is examined, and the envisioned 5G NR for localization enhancement, and the future research direction are explored.

翻译：高效定位在无人地面车辆（UGV）与无人机（UAV）的众多现代应用中起着至关重要的作用，有助于提升控制性能、安全性、能源经济性等。无处不在的5G NR（新空口）蜂窝网络将为增强无人机与无人地面车辆的定位能力提供新的机遇。本文综述了基于射频（RF）的定位方法。我们梳理了可用于定位的射频特征，并研究了适用于无人驾驶车辆的两大类主流方法：基于距离的定位与指纹定位。文中分析了当前面向无人机与无人地面车辆的射频定位前沿文献，探讨了5G NR在定位增强方面的应用前景以及未来的研究方向。