@InProceedings{LimaFoMaSoSaPaMo:2019:EtDiLb,
author = "Lima Filho, Vicente Carvalho and Marini, Leonardo Pereira and
Soussantos, Jonas and Salles, Lucas Alves and Paula, Eurico
Rodrigues de and Moraes, Alison O.",
affiliation = "{Instituto Tecnol{\'o}gico de Aeron{\'a}utica (ITA)} and
{Instituto Tecnol{\'o}gico de Aeron{\'a}utica (ITA)} and
{Instituto Tecnol{\'o}gico de Aeron{\'a}utica (ITA)} and
{Instituto Tecnol{\'o}gico de Aeron{\'a}utica (ITA)} and
{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto
de Aeron{\'a}utica e Espa{\c{c}}o (IAE)}",
title = "The eta-mi distribution for L-band ionospheric amplitude
scintillation modeling and the evaluation of GBAS CAT I services
under low latitude regions",
year = "2019",
organization = "ION International Technical Meeting",
abstract = "The 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 S{\~a}o Jos{\'e} 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.",
conference-location = "Reston, Virginia",
conference-year = "28-31 jan.",
language = "en",
urlaccessdate = "09 maio 2024"
}