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Spirent KB Article
Doc ID: FAQ18565
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GNSS: What are the default signal power levels used by PosApp for the GNSS constellations, and why are these values used?
The guaranteed minimum power level of the received GNSS RF signal is specified in the Interface Control Document (ICD) for each constellation. To accurately simulate GNSS signals, Spirent uses these levels as a reference.
The received power level can vary due to (but not limited to):
Satellite deviation (within admissible range) from nominal orbit altitude (perturbation)
Differing values of gain of satellite transmitting antennae
By using a guaranteed minimum received power level as specified in the ICD, PosApp has a baseline reference for each constellation.
For selected constellations, PosApp uses the following guaranteed minimum received power levels
GPS -130 dBm
GLONASS -131 dBm
Galileo -122 dBm
Beidou -133 dBm
IRNSS -130 dBm
SBAS -130 dBm (WAAS, EGNOS, MSAS, GAGAN)
If your scenario uses constellations with different reference levels (for example GPS and Galileo), the Power Levels Graph within the GUI shows the text “Ref” instead of a power level in dBm, as can be seen in Fig 1 and Fig 2 below.
Fig 1. GPS L1 only. Reference power level of -130dBm.
Fig 2. GPS L1 and Galileo E1. Reference power level changes to “Ref”.
Each frequency within a constellation (GPS L1 (-130dBm), L2 (-136dBm) and L5 (-127.9dBm) for example) may have different minimum received power levels. Please refer to each constellation’s ICD for these different levels.
Product : PosApp