Combined Tracking Strategy Based on Unscented Kalman Filter for Global Positioning System L2C CM/CL Signal

Xuefen Zhu; Fei Shen; Jianfeng Chen; Yang Yang; Dongrui Yang; Xiyuan Chen

doi:10.14429/dsj.65.8725

Xuefen Zhu School of Instrument Science and Engineering, Southeast University, Nanjing
Fei Shen School of Instrument Science and Engineering, Southeast University, Nanjing
Jianfeng Chen Automotive Engineering Research Institute, Jiangsu University, Zhenjiang
Yang Yang School of Instrument Science and Engineering, Southeast University, Nanjing
Dongrui Yang School of Instrument Science and Engineering, Southeast University, Nanjing
Xiyuan Chen School of Instrument Science and Engineering, Southeast University, Nanjing

DOI: https://doi.org/10.14429/dsj.65.8725

Keywords: global positioning system, GPS receiver, tracking algorithm, unscented Kalman filter, CM/CL signal, weighting assignment

Abstract

In a global positioning system receiver, the tracking algorithm plays a dominant role since the code delay and Doppler frequency shift need to be accurately estimated as well as their variation over time need to be continuously updated. Combine unscented Kalman filter (UKF) with CM/CL signal to improve the signal tracking precision is proposed. It allow weighting assignment between CM code and CL code incoming signal, masked by a mass of noise, and to describe a UKF tracking loop aiming at decreasing numerical errors. UKF here involves state and measuring equations which calculate absolute offsets to adjust initial code and carrier phase then dramatically decrease the tracking error. In particular, the algorithm is implemented in both open space and jammed environment to highlight the advantages of tracking approach, by comparing single code and combined code, UKF and EKF tracking loop. It proves that signal tracking based on UKF, with low energy dissipation as well as high precision, is particularly appealing for a software receiver implementation.