Position, Navigation, and Timing (PNT) Through Low Earth Orbit (LEO) Satellites: A Survey on Current Status, Challenges, and Opportunities

More and more satellites are populating the sky nowadays in Low Earth orbits (LEO). Most of targeted applications related to broadband narrowband communications, observation, synthetic aperture radar, internet-of-Things (IoT) connectivity. In addition these applications, there is yet-to-be-harnessed potential for LEO positioning, navigation, timing (PNT) systems, or what referred as LEO-PNT. No commercial LEO-PNT solutions currently exist no unified research on concepts. Our survey aims fill gaps knowledge regarding a system entails, its technical design steps challenges, physical layer parameters viable solutions, tools can be used (e.g., optimisation steps, hardware software simulators, etc.), existing models wireless channels satellite-to-ground ground-to-satellite propagation, prospects future system. A comprehensive multidisciplinary provided by team authors with complementary expertise signal processing, navigation tracking, physics, machine learning, remote sensing, digital economy, business models.