Comparison of MEO, LEO, and Terrestrial IoT Configurations in Terms of GDOP and Achievable Positioning Accuracies

Abstract

Complementary solutions to the Medium Earth Orbit (MEO) Global Navigation Satellite Systems (GNSS) are more and more in demand to be able to achieve seamless positioning worldwide, in outdoor as well as in indoor scenarios, and to cope with increased interference threats in GNSS bands. Two of such complementary systems can rely on the emerging Low Earth Orbit (LEO) constellations and on the terrestrial long-range Internet of Things (IoT) systems, both under rapid developments nowadays. Standalone positioning solutions based on such systems complementary to GNSS can be beneficial in situations where GNSS signal is highly affected by interferences, such as jammers and spoofers, while hybrid GNSS and non-GNSS solutions making use of LEO and terrestrial IoT signals as signals of opportunity can improve the achievable positioning accuracy in a wide variety of scenarios. Comparative research of performance bounds achievable through MEO, LEO, and terrestrial IoT signals are still hard to find in the current literature. It is the goal of this paper to introduce a unified framework to compare these three system types, based on geometry matrices and error modeling, and to present a performance analysis in terms of Geometric Dilution of Precision (GDOP) and positioning accuracy bounds.

Is LEO-Based Positioning with Mega-Constellations the Answer for Future Equal Access Localization?

“…This sub-section presents a comparison of LEO and MEObased performance metrics in terms of positioning. Two performance metrics were selected for this purpose: the indoor received C/N 0 and GDOP [1]. We used Starlink, Oneweb, and Kuiper as representatives of LEO constellations, operating at 12-20 GHz (Ku/K bands), and Galileo and GPS as representative of MEO constellations, operating at 1.575 GHz (L-band).…”

“…The C/N 0 is a well known metric in navigation community, referring at the signal-to-noise ratio in the desired bandwidth and thus measured in dB-Hz units; it basically measures how well a signal could be acquired and further processed indoors; the higher C/N 0 , the better the acquisition. GDOP is a measure of how good the geometry of the satellites position is and readers can find its detailed definition for example in [1]; the smaller the GDOP, the better the geometry, and thus the better the positioning accuracy.…”

“…The alternative could be the use of universally accessible signals, such as those coming from satellite systems with wide Earth coverage. Both MEO GNSS and LEO mega constellations have currently excellent coverage outdoors [1] and even higher coverage is expected in the next 5-10 years with the future LEO constellations.…”

“…An additional challenge is the tradeoff between the number of satellites and achieved coverage, as it takes several LEO satellites on orbit to match the footprint of one MEO satellite. This challenge is easily overcome by the huge total number of LEO satellites to be launched on sky in the next few years [1]. Another challenge is that smaller satellites and cheaper transmitters in LEO systems result in less stable clocks, higher clock inaccuracies, higher phase noises and I/Q imbalances, and higher non-linearities of the components than in MEO, which pose additional constraints on the LEObased PNT.…”

“…Our paper offers a feasibility study of the potential usage of LEO satellites mega-constellations for equal-access localization, by summarizing the opportunities provided by LEO signals, the unsolved challenges, as well as solutions to address these challenges. An illustrative scenario is also included, to compare LEO and MEO indoor coverage in terms of received Carrier-to-Noise ratio (C/N 0 ) and Geometric Dilution of Precision (GDOP), which are two known and widely used metrics in navigation community [1], [2].…”