Ionosphere Scintillation-Induced Deep Fades

Brian Breitsch\(^1\)      Jade Morton\(^1\)

Dongyang Xu \(^2\)      Yang Rong \(^1\)

and Their Effect on GNSS Carrier Phase

ION/IEEE PLANS 2018

1. University of Colorado Boulder

2. Colorado State University

Motivation: Impact of Deep Fades Due to Ionosphere Scintillation

Theory: Scintillation Simulation and Modeling Deep Fades

Data: Examples of Canonical Fades and Fulle-Cycle Transitions

Next Steps: Triple-Frequency Potential for Mitigation and Correction

Carrier Phase Measurement

\Phi_i = G + I_i + B_i + S_i

IONOSPHERE  ERROR

AMBIGUITY / BIAS TERMS

SYSTEMATIC ERRORS / SCINTILLATION / MULTIPATH

FREQUENCY INDEPENDENT EFFECTS

carrier frequency \(f_i\)

I_i \approx -\frac{\kappa}{f_i^2} \text{TEC}

particularly present in signals from satellites at low elevation

Triple-Frequency Range and TEC Estimates

\text{TEC} = \displaystyle -\frac{\Phi_1 - \Phi_2}{\kappa \left(\frac{1}{f_1^2} - \frac{1}{f_2^2}\right)}
G = \displaystyle \frac{f_1^2 \Phi_1 - f_2^2 \Phi_2}{f_1^2 - f_2^2}

ionosphere-free

geometry-free

Dual-Frequency Analogy:

\text{G} = 2.3 \cdot \Phi_\text{L1} - 0.3 \cdot \Phi_\text{L2} - 1.0 \cdot \Phi_\text{L5}

Ionosphere-Free Range Estimate

\text{TEC} = 8.3 \cdot \Phi_\text{L1} - 2.9 \cdot \Phi_\text{L2} - 5.4 \cdot \Phi_\text{L5}

Geometry-Free TEC Estimate

\Phi_i = G + I_i + B_i + S_i

(they exist)

Ionosphere Scintillation

L5

L2

L1

ionosphere phase screen

2013, Ascension Island, PRN 24

fading of 15 to 20 dB or more in signal amplitude

Deep Fading

canonical fades: associated with half-cycle phase changes

L5

L2

L1

Impact on Range and TEC Estimates

Motivation: Impact of Deep Fades Due to Ionosphere Scintillation

Theory: Scintillation Simulation and Modeling Deep Fades

Data: Examples of Canonical Fades and Fulle-Cycle Transitions

Next Steps: Triple-Frequency Potential for Mitigation and Correction

Simulating Scintillation

  • stochastic scintillation realizations using iterative parameter estimation (IPE) technique

fit real SI PSD to scintillation theory

generate random field realizations

simulation

Simulating Scintillation

shows validation of occurrence of full-cycle transitions during canonical fades

simulation

Modeling Deep Fades

A_1 \exp(\phi_1) + A_2 \exp(\phi_2)
A_1 \exp(\phi_1) \left(1 + \alpha \exp(\Delta \phi) \right)

detrended scintillation: colored complex noise

What Can Happen To Phase During a Deep Fade?

Motivation: Impact of Deep Fades Due to Ionosphere Scintillation

Theory: Scintillation Simulation and Modeling Deep Fades

Data: Examples of Canonical Fades and Fulle-Cycle Transitions

Next Steps: Triple-Frequency Potential for Mitigation and Correction

Phase Behavior in Real Data

L5

L2

L1

Phase Behavior in Real Data

L5

L2

L1

Phase Behavior in Real Data

L5

L2

L1

Motivation: Impact of Deep Fades Due to Ionosphere Scintillation

Theory: Scintillation Simulation and Modeling Deep Fades

Data: Examples of Canonical Fades and Fulle-Cycle Transitions

Next Steps: Triple-Frequency Potential for Mitigation and Correction

Information From Triple-Frequency Measurements

\text{GIFC} = 0.226 \cdot \Phi_\text{L1} - 1.226 \cdot \Phi_\text{L2} + 1.0 \cdot \Phi_\text{L5}

Geometry-Ionosphere-Free Combination

deep fading

deep fading

Geometry-Ionosphere-Free Combination

potential use in identifying / correcting full-cycle transitions

Take-Aways

  • strong ionosphere scintillation contains deep fades with associated canonical fade phase behavior

 

  • sometimes, these canonical fades are associated with full-cycle phase transitions, which cause large errors in TEC and range measurements​

 

  • multi-frequency signal measurements are necessary to discriminate when full-cycle transitions occur

Next Steps

  • detect and remove full-cycle transitions
  • improve tracking performance during deep fading

Acknowledgements

This research was supported by the Air Force Research Laboratory.

Contact

Brian Breitsch

brianbreitsch@gmail.com