Accuracy limits in multi-GNSS.

Satellite navigation is quickly becoming a multidimensional complex challenge, with four Global Navigation Satellite Systems (GNSS) fully or partially deployed, more than 90 GNSS satellites currently in the sky, and 12 open-service GNSS signal types available to the end-user. Research papers about GNSS performance typically focus on single or dual GNSS solutions, and there are still very few papers addressing jointly the four existing GNSS together. It is the goal of our paper to present a unified, fast, modular, and simple-to-program theoretical analysis of the four GNSS, focusing on performance limits in terms of spectral characteristics, tracking, multipath robustness, and positioning accuracy. A unified new compact approach for dealing with all the modulations employed in GNSS is also included.We show a unified generic framework for analyzing the multi-GNSS signals in a fast and simple-to-implement manner, without the need of simulating constellations or gathering measurement data. Our approach is also validated with Spectracom-based constellation data. Our analysis can be used as the starting point in further design process or system analysis. [ABSTRACT FROM AUTHOR]