Evaluation of Deep Signal Fading Effects Due to Ionospheric Scintillation on GPS Aviation Receivers

Jiwon Seo, Todd Walter, Tsung-Yu Chiou, Juan Blanch, Per Enge

Abstract:	Deep and frequent GPS signal fading due to strong ionospheric scintillation is major concern for aircraft navigation in the equatorial region during solar maximum periods. Deep signal fading can break a receiver’s carrier tracking lock on a satellite channel and the satellite cannot be used for position solution until a receiver reacquires the lost channel. Frequent signal fading also causes frequent reset of the carrier smoothing filter of aviation receivers. Aviation receivers reduce code noise by as much as a factor of 10 by using carrier smoothing, but frequent loss of lock reduces the effective smoothing time and significantly increases the effect of code noise. This paper analyzes navigation availability during a strong scintillation period based on real scintillation data from the previous solar maximum. Both effects from satellite loss due to deep fading and shortened carrier smoothing time due to frequent fading are considered for the availability simulation. The strong scintillation data for this research was collected in 2001 with early IF (Intermediate Frequency) capture technology. This paper discusses possible C/No (carrier to noise density ratio) increases through improved receiver technology. C/No gain reduces a receiver’s probability of loss of lock in the scintillation environment. Various probabilities of loss of lock are considered for the availability simulation in order to assess the benefit of a current receiver technology during strong scintillation. Availability results for vertical navigation (LPV 200) and horizontal navigation (RNP 0.1) during strong scintillation are illustrated as availability contours and the clear benefit of shorter reacquisition time is emphasized. Finally, a change of reacquisition time limit of the current WAAS MOPS (Minimum Operational Performance Standards) [1] is recommended based on the availability simulation results and observed reacquisition times of a certified WAAS receiver for 36 days in Brazil.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	2397 - 2404
Cite this article:	Seo, Jiwon, Walter, Todd, Chiou, Tsung-Yu, Blanch, Juan, Enge, Per, "Evaluation of Deep Signal Fading Effects Due to Ionospheric Scintillation on GPS Aviation Receivers," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 2397-2404.
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