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Positioning Application: How do I choose the value of channel de-correlation time in the Cornell Ionospheric Scintillation model parameters?

Environment/Versions
  • PosApp
  • SimGEN
  • All GNSS constellation simulators
Answer
The channel de-correlation time controls the scintillation response time and remains fixed throughout the scenario:
  •          Low values of τ0 indicate rapidly varying scintillation.
  •          High values of τ0 indicate slowly varying scintillation .

The scintillation response time, τ0, is defined in the following reference:
  • Simulating Ionosphere-Induced Scintillation for Testing GPS Receiver Phase Tracking Loops, Humphreys et al., IEEE Journal of Selected Topics in Signal Processing, 3, No 4, pp 707 - 715. http://ieeexplore.ieee.org/document/5166615/

In simplified terms, the de-correlation time effectively means the period over which the scintillation model is applied to the signal amplitude:
  • Using a simulation iteration rate of 10 ms and τ0 = 1s effectively means that the model for amplitude variation is correlated over 100 data points - amplitudes between these data points are similar to each other (or have a similar trend).
  • In contrast, for τ0 = 0.5 s the model will be correlated over a span of 50 data points, and only 50 consecutive data points will be similar to each other (or have a similar trend).
  • Therefore, a smaller τ0 increases the rapidity of the fluctuations resulting in stronger scintillation, while larger τ0 decreases the rapidity of fluctuations, thus simulating weaker scintillation.
It is ultimately at the user's discretion to choose a value for channel de-correlation time appropriate to the test case and in keeping with the definitions of the Cornell model.

Product : Positioning,SimGEN,PosApp