Survey on Opportunistic PNT With Signals From LEO Communication Satellites

Positioning, Navigation, and Timing (PNT) is an essential service for modern societies, their industries, and governmental organizations. Mobility, logistics, and agriculture, among others, depend heavily on reliable PNT and will do so even more in the future. However, the predominant Global Navigation Satellite Systems (GNSS) are highly susceptible to jamming and spoofing, a threat that has increased in the recent years. As a result, there is a growing need for a robust, independent PNT backup system. A promising approach to meet this demand is to use the communication signals of satellites in Low Earth Orbit (LEO) as signals of opportunity (opportunistic LEO-PNT). In recent years, opportunistic LEO-PNT has gained relevance in academic research due to the emergence of megaconstellations. This survey provides an holistic overview of opportunistic LEO-PNT and an exhaustive review of the academic work in the field. Error sources and challenges with respect to the development of operational systems are evaluated, and the state of the art performance is analyzed. System-level strategies to mitigate the error sources and challenges are identified, including the combination of opportunistic LEO-PNT with GNSS or other sensors, or the use of base stations. Future research directions, such as the investigation of non-accuracy related KPIs, the required receiver hardware, or the use in low SNR scenarios, are derived.