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Positioning Application: How do I choose the value of channel de-correlation time in the Cornell Ionospheric Scintillation model parameters?
All GNSS constellation simulators
The channel de-correlation time controls the scintillation response time and remains fixed throughout the scenario:
Low values of τ
indicate rapidly varying scintillation.
High values of τ
indicate slowly varying scintillation .
The scintillation response time, τ
, 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.
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 τ
= 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 τ
= 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 τ
increases the rapidity of the fluctuations resulting in stronger scintillation, while larger τ
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