Implementation and Comparison of EKF and UKF Based Tracking Loop at Low Carrier-to-Noise Ratio Conditions

Abstract

The carrier and code phases tracking is the central work of Global Position System (GPS) receivers. A number of algorithms have been developed to improve the performance of the receivers in tracking the carrier and code phase in challenging environments, such as the Extended Kalman Filter (EKF) and the Unscented Kalman Filter (UKF). This paper uses GPS software receiver to implement the algorithms, provides details about the implementation, deeply compares the two different methods and takes into consideration different numbers of measurements. To evaluate the performance effectively, some criterions to compare these two algorithms are proposed. The results show although both algorithms have satisfying performance in tracking weak signals, the UKF exceeds in some aspects. The results also indicate that algorithms with more measurements in the measurement model could track the signals more accurately, but the outperformance becomes less obvious when the number of measurements surpasses certain threshold.