Title: Galileo Ionospheric Correction Algorithm: An Optimization Study of NeQuick-G
Citation: RADIO SCIENCE vol. 54 no. 11 p. 1156-1169
Publication Year: 2019
JRC N°: JRC117408
ISSN: 0048-6604 (online)
URI: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2019RS006875
DOI: 10.1029/2019RS006875
Type: Articles in periodicals and books
Abstract: At present most low-cost GNSS receivers operate one frequency in the L band. For them one of the largest error contributions is the delay of radio signals in the Ionosphere. NeQuick-G is the official ionospheric correction algorithm (ICA), which has been adopted for Galileo, the European GNSS Programme. The NeQuick-G implementation is complex when compared with other ICAs. It is also demanding in terms of computational resources. The Joint Research Centre completed a reference implementation of NeQuick-G based on the official document “Ionospheric Correction Algorithm for Galileo Single Frequency Users” provided by the European Global Navigation Satellite Systems Agency. The rationale behind the JRC implementation of NeQuick-G was the intent to write an independent source code from scratch, without using the pseudo-codes from the reference document and solely relying on the physics descriptions. Using such implementation as baseline, this paper describes an optimization attempt of the official pseudo code from an algorithmic perspective. The objective was to reduce the computational load while not sacrificing the performance. The new proposed integration method is able to speed up calculations to 21% and 49% with respect the two official integration algorithms. The overall computational burden depends on the number of operations, which is eventually closely correlated to the number of calls of the ionospheric model. This underlines the quest to find an integration method reducing this number of calls. Moreover, based on the findings of this study, the authors strongly recommend revisiting the convergence control of the integration routines introduced in (Galileo OS-ICA, 2016).
JRC Directorate:Space, Security and Migration

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