On the Ground and in the Sky: A Tutorial on Radio Localization in Ground-Air-Space Networks

TL;DR

This paper tackles radio localization in ground-aerial-space GAS networks, arguing that localization must be designed as a core service within GAS rather than a byproduct of communications. It provides a comprehensive tutorial that spans GAS system modeling, anchor/target characterization, 3D localization fundamentals, and detailed analysis of localization systems for ground, aerial, and space anchors, including preliminary results. The work also investigates design aspects for 5G ground localization and advanced 6G enablers such as RIS, JCAS, AI, CF-mMIMO, and THz, along with key performance indicators and 6G KVIs. By detailing cross-segment localization challenges and opportunities, the paper lays out a path for centimeter-level GAS localization in 6G and beyond, with emphasis on robustness, scalability, and global accessibility.

Abstract

The inherent limitations in scaling up ground infrastructure for future wireless networks, combined with decreasing operational costs of aerial and space networks, are driving considerable research interest in multisegment ground-air-space (GAS) networks. In GAS networks, where ground and aerial users share network resources, ubiquitous and accurate user localization becomes indispensable, not only as an end-user service but also as an enabler for location-aware communications. This breaks the convention of having localization as a byproduct in networks primarily designed for communications. To address these imperative localization needs, the design and utilization of ground, aerial, and space anchors require thorough investigation. In this tutorial, we provide an in-depth systemic analysis of the radio localization problem in GAS networks, considering ground and aerial users as targets to be localized. Starting from a survey of the most relevant works, we then define the key characteristics of anchors and targets in GAS networks. Subsequently, we detail localization fundamentals in GAS networks, considering 3D positions, orientations, and velocities. Afterward, we thoroughly analyze radio localization systems in GAS networks, detailing the system model, design aspects, and considerations for each of the three GAS anchors. Preliminary results are presented to provide a quantifiable perspective on key design aspects in GAS-based localization scenarios. We then identify the vital roles 6G enablers are expected to play in radio localization in GAS networks.

Figures (13)

• Figure 1: A representation of the different segments and elements of integrated GAS networks and the typical altitude of the various non-terrestrial elements.
• Figure 2: The levels of drones' well-clear (WC) zones each represented by a cylinder. The red cylinder represents the collision avoidance (CA) zone. For a given drone, the percentage values showed at its WC cylinders represent the probability of another drone present in a given cylinder violating/entering the next smaller CA cylinder vinogradov2020wireless. E.g., the probability of a drone present in the yellow CV cylinder entering the orange CV cylinder is 6.75%.
• Figure 3: An example of (a) yaw, (b) pitch, and (c) roll rotation angles performed, with right-hand rule in mind, on a uniform rectangular array of antennas. The figure shows a yaw, pitch, and roll in their corresponding positive rotation direction.
• Figure 4: A representation of the localization measurables, which include distances and angles.
• Figure 5: Primary snapshot localization methods.