Receiver architectures for positioning with low earth orbit satellite signals: a survey

Positioning, Navigation and Timing (PNT) are services generally provided by Global Navigation Satellite Systems (GNSS). GNSS reside in medium to high orbital altitudes from the Earth's surface, resulting in weak signal reception. However, user applications are increasingly in need of higher power signal strength or alternative PNT solutions. An influx of satellites in Low Earth Orbit (LEO) are driving such innovation in PNT technology. Improved signal strength compared to GNSS can be obtained from LEO satellites merely due to their proximity to Earth. Therefore, even communication satellite transmissions are becoming appealing to navigation, as so-called Signals of OPportunity (SOP). In order to benefit user applications, the receiver architectures for LEO-SOP, as well as potential LEO-PNT signals are explored.