Inside GNSS Media & Research

JUL-AUG 2018

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www.insidegnss.com J U L Y / A U G U S T 2 0 1 8 Inside GNSS 35 manner. e power profile is then repeated a second time. e profile of this test methodology is illus- trated in Figure 4. In order to assess the performance of the RUT in the presence of interfer- ence, different metrics were selected. e following outputs from the GNSS receiver are recorded and analyzed for all the test methodologies: • Number of tracked satellites • Position fix indicator (a Boolean to indicate if a 3D position fix is avail- able or not) • Number of satellites used in fix • Carrier-to-Noise density (C/N 0 ) ratio • East-North-Up position error Moreover, depending on the test methodology, additional parameters are evaluated. For example, in the case of the TTRP test method, the time taken for the RUT to re-obtain a position fix aer a strong interference event is measured. For the sensitivity test method, the Jamming-to-Signal ratio at which the position solution is no longer available and the availability of the position solution during the interference event are computed. Fur- thermore, position accuracy statistics are computed for the interval in which the interference is present when the receiver offers a valid position fix. Currently, only GPS L1 and Galileo E1 signals are used for testing and the RUT is configured to operate in static stand-alone mode. Table 1 provides an overview of the FIGURE 3 TTRP test profile Simulation starts 30 minutes Simulation ends FIGURE 4 Sensitivity test profile Simulation starts 60 minutes Simulation ends Constellation GPS + Galileo Centre frequency (MHz) 1575.42 Ionosphere model Klobuchar Troposphere model Saastamoinen Start time 01.02.2018 – 12:00:00 Duration (min) 30 (TTRP) / 60 (sensitivity and baseline) GNSS signal power (dBm) -125 Interference power level for 'TTRP test method' (dBm) -35 Interference power range for 'Sensitivity test method' (dBm) [-120:5:-60] J/S range for 'Sensitivity test method' (dB) [5:5:65] Receiver location (Lat/Long/Alt) 60°N/24°E/30m Table 1. Simulated scenario settings C/N 0 threshold for satellite in PVT computation (dB-Hz) Default receiver specific value Minimum elevation angle 5° Start-up state Cold start Positioning mode Static stand-alone Table 2. RUT settings

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