Development of Kalman filter-based GPS/LEO navigation receiver

In this study, a Kalman filter (KF)-based Global Positioning System (GPS)/low-Earth-orbit (LEO) navigation receiver was developed. Iridium Next was the target constellation for the extraction of Doppler measurements by this receiver. The proposed KF-based receiver was designed to maintain Doppler tracking for Iridium Next satellites over brief periods when signal bursts are not present; thus, this receiver can generate continuous Doppler shift measurements. The signal models of Iridium Next and Orbcomm were analyzed, after which a KF-based LEO navigation algorithm was developed and incorporated into a conventional GPS navigation receiver. Moreover, an extended-KF-based GPS/LEO positioning algorithm was developed to ensure that the designed KF-based GPS/LEO receiver can achieve accurate navigation. Experiments were conducted under open-sky conditions to compare the navigation performance of the proposed KF-based receiver and that of a fast Fourier transform (FFT)-based GPS/LEO receiver. The experimental results revealed that the KF-based receiver exhibited marginally larger Doppler shift measurement errors but extracted considerably more Doppler measurements than did the FFT-based receiver. This advantage of the KF-based receiver is attributed to its capability of maintaining Doppler tracking during brief periods of signal absence. Positioning solutions were obtained using various combinations of GPS and Iridium Next satellites, and these solutions indicated the suitability of integrating LEO satellite signals into the GPS. The inclusion of Iridium Next satellites into the GPS improved positioning accuracy, especially in challenging environments with limited GPS satellite coverage. The KF-based receiver minimized positioning errors to a slightly greater extent than did the FFT-based receiver. Overall, the results of this study verify the potential and benefits of incorporating LEO satellite signals into the GPS for enhancing the reliability and accuracy of navigation systems in diverse operational environments.