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Session A3: Atmospheric Effects, GNSS Remote Sensing and Scientific Applications

A Method for Simulating Dynamic Ionosphere Scintillation
Brian Breitsch, Andrew Sun, Jade Morton, University of Colorado Boulder
Location: Seaview Ballroom
Date/Time: Wednesday, Jan. 24, 4:46 p.m.

Peer Reviewed

The ionosphere remains a significant source of error impacting signals transmitted from Global Navigation Satellite Systems (GNSS), especially during times of peak solar activity. While large unpredictable fluctuations in TEC cause meter-level errors in position solutions, an even more pernicious ionosphere impact is scintillation, which manifests as random fluctuations in the received signal phase and amplitude. These random fluctuations can cause receiver tracking errors, carrier phase cycle slips, and loss-of-lock. Because scintillation is a random phenomenon, there are inherent limits to how well a receiver can mitigate its effects. It is therefore important to be able to simulate ionosphere scintillation effects in order to study the extent of its impacts on receiver integrity.
To this end, various models have been developed, such as [1] that extracts the statistical distributions of scintillating amplitude and phase and uses them to generate random scintillation simulations. This model is useful for testing receiver tracking loop performance and robustness. It should be noted, however, that it does not accurately capture multi-frequency coherence or the effect of scintillation-induced cycle slips, or phase transitions. Alternatively, a physics-based phase screen model of ionosphere propagation can be used to simulate realistic scintillation at multiple signal frequencies and accurately captures signal phase behavior [2]. In the simplest case, the scintillation phase screen can be parameterized by the intensity (S4) and decorrelation time (? ) of amplitude fluctuations [3], [4], which helps relate results obtained using these simulations back to real-world scintillation observations. While phase screen models have proven useful for testing robust tracking algorithms [5] and for assessing the role of scintillation in causing cycle slips [6], they are also inherently limited by their assumption of stationary scintillation parameters over the simulation duration. Testing receivers in a more operationally realistic setting, in which scintillation characteristics evolve over time, will require the simulation of dynamic, long-duration scintillation time series.
In this work, we present one possible means to accomplish this, called “scintillation stitching,” whereby several stationary simulations are combined to create longer, non-stationary scintillation simulations. The hope is that this makes scintillation simulations more useful to GNSS simulators that need to test the robustness of operational receivers. In Section II, we provide some background on GNSS measurement and phase screen scintillation models that we consider in this work. Then, in Section III, we introduce the scintillation stitching method and discuss relevant parameters and implementation. In Section IV, in order to demonstrate use of this method, we consider results of applying a simple 2nd-order phase-lock loop (PLL) to non-stationary scintillation measurements. Finally, in Section V, we provide concluding remarks.



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