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1. Identity statement
Reference TypeConference Paper (Conference Proceedings)
Sitemtc-m21c.sid.inpe.br
Holder Codeisadg {BR SPINPE} ibi 8JMKD3MGPCW/3DT298S
Identifier8JMKD3MGP3W34R/3SMU5GP
Repositorysid.inpe.br/mtc-m21c/2019/02.08.15.53
Metadata Repositorysid.inpe.br/mtc-m21c/2019/02.08.15.53.24
Metadata Last Update2020:01.06.11.42.09 (UTC) administrator
Secondary KeyINPE--PRE/
Citation KeyLimaFoMaSoSaPaMo:2019:EtDiLb
TitleThe eta-mi distribution for L-band ionospheric amplitude scintillation modeling and the evaluation of GBAS CAT I services under low latitude regions
Year2019
Access Date2024, June 15
Secondary TypePRE CI
2. Context
Author1 Lima Filho, Vicente Carvalho
2 Marini, Leonardo Pereira
3 Soussantos, Jonas
4 Salles, Lucas Alves
5 Paula, Eurico Rodrigues de
6 Moraes, Alison O.
Resume Identifier1
2
3
4
5 8JMKD3MGP5W/3C9JH2U
Group1
2
3
4
5 DIDAE-CGCEA-INPE-MCTIC-GOV-BR
Affiliation1 Instituto Tecnológico de Aeronáutica (ITA)
2 Instituto Tecnológico de Aeronáutica (ITA)
3 Instituto Tecnológico de Aeronáutica (ITA)
4 Instituto Tecnológico de Aeronáutica (ITA)
5 Instituto Nacional de Pesquisas Espaciais (INPE)
6 Instituto de Aeronáutica e Espaço (IAE)
Author e-Mail Address1
2
3
4
5 eurico.paula@inpe.br
Conference NameION International Technical Meeting
Conference LocationReston, Virginia
Date28-31 jan.
History (UTC)2019-02-08 15:54:08 :: simone -> administrator :: 2019
2020-01-06 11:42:09 :: administrator -> simone :: 2019
3. Content and structure
Is the master or a copy?is the master
Content Stagecompleted
Transferable1
Content TypeExternal Contribution
AbstractThe usage of the GNSS is a world trend among the new technologies for air navigation. Within this context, the FAA developed the Ground-Based Augmentation System (GBAS) to improve accuracy, integrity, and continuity of the GNSS positioning through the augmentation of the GPS observables, in order to support precision approach landings. The GBAS can be considered a safety-critical system due to the precision landing requirements defined by ICAO. The ionospheric layer generates significant interference in the satellite signals and is one of the most threatening issues for the GBAS. Ionospheric scintillation may cause severe damage in the GPS receiver tracking loop operations. In moderated events, scintillation can reduce the accuracy of GPS pseudorange and carrier measurements, but the receiver still remains in lock. The tracking loop performance is degraded by scintillation fades that eventually lead to cycle slips. However, during strong scintillation events, the receiver might not be able to handle the large amount of scintillation, loosing its channels because the signal-to-noise ratio drops below the receiver threshold, resulting in a loss of lock. The strong amplitude scintillation phenomena are usual around the equatorial and low-latitude regions, in a belt of approximately ±20o of geomagnetic latitude. These pronounced scintillation events are related to the presence of depleted structures known as Equatorial Plasma Bubbles (EPBs). EPBs rise in the equatorial and low-latitude regions in the nighttime due to the electrodynamic features in the equatorial plasma bulk. In the equatorial and low-latitude region, after the dusk, the elevation uplift of the plasma implies larger vertical gradients in an opposite direction of the gravity forcing, thus setting the system into an unstable equilibrium. If an external perturbation exists, then this equilibrium may be disturbed and the Rayleigh-Taylor instability action may cause the evolution of such kilometric bubble structures. After this initial step, a cascading process originates structures progressively smaller, whose wavelength will interfere deeply in the satellite transionospheric L-band signals causing the strong amplitude scintillation. In the Brazilian territory such events are more intense during spring and summer months, under high solar flux conditions. Nowadays, scintillations due to plasma bubbles affecting satellites signals during the night are the most significant issues that forbid Brazil from providing CAT I services from a GBAS station, considering the current architecture of the system available. This work analyzes high rate (50Hz) measurements of the GPS L1 (1.575GHz) amplitude scintillation data recorded during one month between December 2001 and January 2002 at São José dos Campos, Brazil (Geographic coordinates: 23.20o S, 45.86o W, -17.50o dip latitude), a place located near to the southern crest of the equatorial ionization anomaly. The goal of this study is to evaluate the use of eta-mi probability density function in the statistical characterization of the ionospheric fading events. The analysis was performed comparing the proposed model against other models widely accepted in the literature, like Nakagami-m and Rice models, and additionally, the comparison is extended against the alpha-mi model. The results of the analysis performed showed that the eta-mi distribution presents good results on fitting empirical data of scintillation. This capability may help to better characterize fading events for example for GBAS availability studies. Typical pairs of eta-mi coefficients are presented as well as a discussion about the fading profile based on such values. The comparison of eta-mi distribution to Rice, Nakagami-m and alpha-mi models showed that eta-mi is capable of describing a wide range of scenarios with a fair adjustment in the tail of the distribution. This topological adjustment is an advantage of bivariate distributions like the alpha-mi and eta-mi models in comparison with the single parameter distributions. The fit test results show that the alpha-mi distribution has a similar performance to the eta-mi model, both providing a flexibility that better adjusts to the measured data, in particular in the tail of the distribution. Additionally, in this work the estimation of the fading coefficients eta-mi is explored according to the experimental data, providing empirical values for theoretical works and discussing the benefits of this proposed model and other models adopted in the literature. Equations presenting an approximation useful for theoretical works are also proposed based on the results. Finally, a discussion about the bit error probability and mean time between cycle slips is also included showing estimated values using the eta-mi model. Based on these results, it is analyzed how this geophysical phenomenon may generate unacceptable threatening gradients that, occasionally, will restrict GBAS to operate safely during the nighttime in low latitude regions.
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