A Performance Study on the Combination of Available GNSS and Potential LEO-PNT Constellations

With the reduction in the launch and manufacturing costs of satellites, there has been a surge of interest in Low-Earth Orbit (LEO) satellites from both the industrial and academic sectors in recent years. This heightened interest has led to the growing popularity of the LEO-based Positioning, Navigation, and Timing (LEO-PNT) systems, which are seen either as complementary or standalone alternatives to the current Global Navigation Satellite Systems (GNSS). Studies that explore LEO and GNSS systems together typically do it either from the perspective of LEO-based GNSS augmentation or from the perspective of a standalone LEO system that improves over GNSS. However, there are very few studies that examine the combination of a standalone LEO constellation with GNSS to improve the PNT performances of each. Thus, we take an approach that falls in between the two typical approaches, and we explore the expected performance improvement when standalone LEO and GNSS systems are combined, from a LEO-PNT perspective. For this purpose, we selected three GNSS constellations (GPS, Galileo and BeiDou) as well as two LEO-PNT constellations (Centispace and an experimental design, previously proposed by the Authors), and we analyze their standalone and combined performances in an indoor environment. The simulations are conducted with a MATLAB-based in-house constellation simulator using the QuaDRiGa channel-model library. The results indicate that a combination of two LEO-PNT systems with one or several of the available GNSS constellations can significantly improve the indoor coverage, as well as providing good received signal quality and good geometric configuration quality for indoor positioning when frequency bands similar to GNSS are used for LEO-PNT constellations.