High-accuracy Galileo tracking algorithm with improved convergence for the SDR GNSS

Global navigation satellite systems (GNSSs) are currently used in navigation, surveying, and autonomous systems, and the Galileo constellation is providing improvements in accuracy and availability. Despite these benefits, the tracking stability and convergence performance for Galileo signals via low-cost software-defined radio (SDR) receivers pose challenges as a result of noise, multipath interference and front-end instability. The main purpose of this work was to develop a high-accuracy Galileo tracking algorithm that enhances the convergence ability and tracking robustness with low computational complexity. This paper pushes the envelope of traditional and Frequency Locked Loop (FLL) based tracking in phase-locked loops (PLL) by introducing an adaptive, two-phase tracking loop architecture as a prime embodiment into an open-source SDR framework. The solution was to use the parallel code phase search (PCPS) algorithm for rapid and efficient acquisition, and with a dual-loop adaptive tracking structure by combining Delay-locked loop (DLL) and PLL techniques, improved with optimized loop filters that enable automatic gain control. The novelty of this work lies in the deployment of a circular correlation-based method for acquisition, an adaptive loop filter design and a Kalman-like convergence improvement approach for simultaneous carrier and code tracking. Real-time raw Galileo E1 signals were received via a USRP N210 RF front end, and baseband signal processing was carried out on a host PC for verification. The experimental results demonstrate significant improvements over a conventional SDR receiver model. The proposed algorithm achieved 53–62% reductions in position RMSE, over 50% faster convergence, and a 14% increase in the carrier-to-noise density ratio (C/N₀). The achieved mean PDOP of 2.87 and consistent code-phase stability confirm its robustness under dynamic and low-signal conditions. These findings confirm that the proposed algorithm substantially enhances the reliability and accuracy of SDR-based Galileo receivers. The improved tracking precision, reduced jitter, and faster convergence make the system suitable for real-time high-accuracy navigation and autonomous vehicle applications.