Decentralized FLL-Assisted PLL Design for Robust GNSS Carrier Tracking

This letter presents a decentralized state estimation framework for FLL-assisted PLL design to enhance the GNSS carrier tracking loop capability. Different from the existing centralized structure that fuses the FLL and PLL measurements via a collective filter, this architecture allows the measurements to be distributively filtered in the local state estimators. Thus, the global carrier state can be updated by combining the local estimates through weighting matrices. The proposed decentralized carrier tracking framework ensures high precision phase performance against noisy measurements and preserves intrinsically wider pull-in range in the presence of large Doppler errors, simultaneously. Demonstrative simulations are provided to show that the decentralized framework exhibits excellent robustness against weak signal and high dynamic conditions as compared with the existing centralized carrier tracking method.