Doppler positioning error analysis of Iridium NEXT non-cooperative signals

Given the potential advantages of Low Earth orbit (LEO) satellites in communication, navigation, and other fields, many LEO constellations have been established. However, very few LEO satellites are exclusively used for navigation. Although the method of using LEO carrier signals for positioning has been studied by many researchers, the differences in positioning error are relatively large, and there is a lack of systematic analysis of the factors affecting positioning error. Therefore, this paper focuses on the typical LEO constellation Iridium NEXT, derives a multi-epoch Doppler positioning method of single satellite, analyzes and verifies the influence of factors such as the observation duration of visible satellites, the number of visible satellites, and Doppler frequency error on positioning error. Experiment results show that increasing the observation duration of visible satellites is useful to reduce positioning error in the case of single satellite positioning; adding satellites of different orbits for multi-epoch observations can reduce the value of position dilution of precision (PDOP) by 89 %, significantly reducing positioning error; when given PDOP, positioning error has a linear relationship with frequency error, and the better the spatial geometric structure, the smaller the impact of frequency error on positioning error.