Effects of diffraction by ionospheric electron density irregularities on the range error in GNSS dual‐frequency positioning and phase decorrelation

Abstract

[1] It can be important to determine the correlation of different frequency signals in L band that have followed transionospheric paths. In the future, both GPS and the new Galileo satellite system will broadcast three frequencies enabling more advanced three frequency correction schemes so that knowledge of correlations of different frequency pairs for scintillation conditions is desirable. Even at present, it would be helpful to know how dual-frequency Global Navigation Satellite Systems positioning can be affected by lack of correlation between the L1 and L2 signals. To treat this problem of signal correlation for the case of strong scintillation, a previously constructed simulator program, based on the hybrid method, has been further modified to simulate the fields for both frequencies on the ground, taking account of their cross correlation. Then, the errors in the two-frequency range finding method caused by scintillation have been estimated for particular ionospheric conditions and for a realistic fully three-dimensional model of the ionospheric turbulence. The results which are presented for five different frequency pairs (L1/L2, L1/L3, L1/L5, L2/L3, and L2/L5) show the dependence of diffractional errors on the scintillation index S4 and that the errors diverge from a linear relationship, the stronger are scintillation effects, and may reach up to ten centimeters, or more. The correlation of the phases at spaced frequencies has also been studied and found that the correlation coefficients for different pairs of frequencies depend on the procedure of phase retrieval, and reduce slowly as both the variance of the electron density fluctuations and cycle slips increase.Citation: Gherm, V. E., N. N. Zernov, and H. J. Strangeways (2011), Effects of diffraction by ionospheric electron density irregularities on the range error in GNSS dual-frequency positioning and phase decorrelation, Radio Sci., 46, RS3002,

Assessment of GPS Multifrequency Signal Characteristics During Periods of Ionospheric Scintillations from an Anomaly Crest Location

“…If signal fades at two frequencies are highly correlated, the actual aim of the frequency diversity scheme would be defeated. As Global Navigation Satellite Systems (GNSS) satellites will broadcast three frequencies enabling more advanced three frequency correction schemes, understanding the correlation between different frequency pairs under scintillation conditions is extremely important (Gherm et al, ). Previously, the assessment of the contribution of diffraction for range errors in the dual‐frequency regime using a hybrid model has been reported in literature (Gherm, Novitsky, et al, ; Gherm, Zernov, et al, ).…”

Strong scintillation of GNSS signals in the inhomogeneous ionosphere: 2. Simulator of transionospheric channel

“…This was the physical background for the Hybrid Scintillation Propagation Model (HSPM) [Gherm et al, 2005], which combined the complex phase (extended to the case of the inhomogeneous background medium Rytov's) method to describe propagation in the inhomogeneous fluctuating ionosphere (weak or moderate scintillation), providing normal distribution for log amplitude and phase fluctuations and the rigorous random (not pure phase) screen technique producing the field strong scintillation. A lot of fine effects of propagation in the regime of strong scintillation formed below the ionosphere when propagating from the bottom of the ionosphere down to the Earth's surface have been described by the HSPM [Gherm et al, 2011;Zernov et al, 2009Zernov et al, , 2012. On the contrary, in the case of full saturation, the field amplitude has the Gaussian (sometimes termed as normal or exponential) distribution, whereas the distribution of the phase in the principal value range (Àπ, π) (termed as wrapped phase) can be considered to be uniform.…”

Strong scintillation of GNSS signals in the inhomogeneous ionosphere: 1. Theoretical background

“…The developed theory forms the theoretical background for constructing the physically based software simulator of the random transionospheric GNSS signals.In the following sections the physically rigorous analytic solution of the problem will be given, which is based on the analytic solutions to the set of the appropriate Markov's parabolic moment equations, written for the case of an essentially inhomogeneous background ionosphere. This should be considered as the extension of the Hybrid Scintillation Propagation Model (HSPM) developed in a series of our papers [Gherm et al, 2005[Gherm et al, , 2011Zernov et al, 2009Zernov et al, , 2012 or its earlier version [Gherm et al, 2000;Maurits et al, 2008], which, in turn, were essentially based on the earlier papers by Zernov [1980] andLundborg [1996].The HSPM is the combination of the Complex Phase Method (CPM), which is the extension of classic Rytov's approximation to the case of the inhomogeneous background medium and the rigorous technique of the random screen (not necessarily phase screen). It describes the strong scintillation of the field, formed when propagating from the bottom of the ionosphere down to the Earth's surface, but is not also valid to describe the case of strong scintillation of the field actually originating inside the inhomogeneous ionospheric layer.…”

“…In the following sections the physically rigorous analytic solution of the problem will be given, which is based on the analytic solutions to the set of the appropriate Markov's parabolic moment equations, written for the case of an essentially inhomogeneous background ionosphere. This should be considered as the extension of the Hybrid Scintillation Propagation Model (HSPM) developed in a series of our papers [Gherm et al, 2005[Gherm et al, , 2011Zernov et al, 2009Zernov et al, , 2012 or its earlier version [Gherm et al, 2000;Maurits et al, 2008], which, in turn, were essentially based on the earlier papers by Zernov [1980] andLundborg [1996].…”