Modeling the impact of equatorial ionospheric irregularities on gps receiver performance
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2012
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Abstract
The performance of a generic GPS receiver caITier tracking loop, subject to ionospheric scintillations, is studied in this thesis via theoretical analyses and simulation results. A physics-based simulation of equatorial scintillations has been employed to provide a full variety of test cases for the simulated carrier tracking loop to assess GPS receiver performance. This simulation tool is novel in allowing oblique signal propagation in an anisotropic medium for multiple frequencies. The scintillation simulation algorithm has been verified through comparison with real scintillation data collected in the equatorial region during the solar maximum of 2001. The utilization of the scintillation simulation tool is demonstrated through applying it to a GNSS signal, and evaluating the subsequent effects on a generic GPS tracking loop model. Theoretical predictions - from the derived equations - are verified through comparison with simulation results According to the studies conducted in this thesis, the effect of phase scintillations on caITier tracking loop error variance is found to be considerably high, even for moderate scintillation levels. In the presence of strong intensity scintillation, the tracking loop's effective caITier-to-noise ratio can be much lower; as a result, the probability of loss of lock can increase and the mean time between cycle slips can decrease significantly. In regard to scintillation effects, the performance of the second-, and third-order caITier tracking loop are very similar. The first-order loop, however, is more fragile as it can lose phase lock at much lower level of scintillation strength. In the presence of scintillation, the choice of the pre-detection integration time does not significantly affect the caITier tracking error variance, provided that the signal's carrier-to-noise ratio level is not very low. The caITier tracking loop requires a relatively wide bandwidth to precisely track changes in the caITier phase due to ionospheric phase scintillation, while requires a naITow bandwidth in order to suppress the effect of signal fading and intensity scintillation. To meet this tradeoff, an optimum bandwidth for minimum tracking error can be determined for the ca1Tier tracking loop in terms of scintillation and tracking loop parameters.
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Bibliography: p. 222-231
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Ghafoori, F. (2012). Modeling the impact of equatorial ionospheric irregularities on gps receiver performance (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/5016