GPS Carrier Parameters Characterization During Strong Equatorial Ionospheric Scintillation

Dongyang Xu, Yu (Jade) Morton

Abstract:	Strong ionospheric scintillation over equatorial regions is characterized by the simultaneous presence of deep signal amplitude fading and random carrier phase fluctuations, which greatly degrade GNSS receiver carrier tracking performance in terms of increased error, cycle slip, and even loss of lock. In order to gain a better understanding of the characteristics of the relationship between the phase scintillation and deep fading, receiver processing algorithms that achieve accurate estimations for amplitude and carrier phase need to be developed. In this paper, utilizing the surveyed position of the scintillation monitoring receiver, a Fixed Position Feedback (FPF) algorithm is developed based on the vector tracking concept [1], which improves the carrier phase estimation during strong scintillation due to its open-loop structure. This algorithm can benefit the carrier phase estimation during deep fading because of two advantages: the ability to separate ionospheric effects from receiver processing artifacts and oscillator effects, and the ability to improve signal intensity during deep fading, resulting in a gain of confidence in the carrier phase estimation. Real GPS L1 scintillation data collected on Ascension Island (S7.9°, W14.4°) during an experimental campaign in March, 2013 are then processed by the FPF algorithm and compared with the output generated by a conventional carrier tracking algorithm using several different integration times. The results reveal fast phase changes of half cycles and full cycles; the former are further confirmed to be true scintillation features through controlled simulated signal tracking. The FPF algorithm with longer integration time results in much reduced cycle slips. The second part of this paper presents the statistical relationship between these sudden half-cycle phase changes and concurrent deep fades. Statistical summary on the tracking results processed by the FPF algorithm on the full collection of the real scintillation data is presented in this paper.
Published in:	Proceedings of the 2015 International Technical Meeting of The Institute of Navigation January 26 - 28, 2015 Laguna Cliffs Marriott Dana Point, California
Pages:	521 - 529
Cite this article:	Xu, Dongyang, Morton, Yu (Jade), "GPS Carrier Parameters Characterization During Strong Equatorial Ionospheric Scintillation," Proceedings of the 2015 International Technical Meeting of The Institute of Navigation, Dana Point, California, January 2015, pp. 521-529.
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