The upcoming challenges on GNSS regarding spoofing, jamming, multipath, and interference, also from multi-constellations, require a detailed analysis on the GNSS signal level. Therefore, a testing method is needed which goes beyond the possibilities of simulations to create a realistic and flexible test environment. The progress in unmanned aerial vehicles (UAV) and software defined radio (SDR) technologies obtained in the last years provide this efficient and flexible approach to mimic GNSS satellites and create a realistic GNSS signal test environment. Within this work we present our experience in setting up a flying test system. Beside UAV and SDR our system includes a positioning and ranging unit to obtain the transmitter-receiver ranges in sub-centimeter and millisecond timestamp accuracy. To eliminate the UAV clock error, two time synchronized receiver units are used. In this first feasibility step we concentrate on a single BPSK(1) on 1576.17 MHz signal and show that the USRP 2950R (NI) can operate in a standalone mode, generating the signal on the FPGA, which is driven by the OCXO onboard clock. It is presented that the recorded Doppler shift represents the UAV motion as well as that the phase pseudorange difference of two antennas can be well (7 cm RMS) matched to the geo-metrical antenna-UAV range difference (cancelation of the SDR clock error). It is shown that the combination of UAV and SDR can be used to mimic a GNSS satellite. Therefore, it is possible to use this arrangement for realistic GNSS signal analyses under various conditions, environments and disturbances.    «

The upcoming challenges on GNSS regarding spoofing, jamming, multipath, and interference, also from multi-constellations, require a detailed analysis on the GNSS signal level. Therefore, a testing method is needed which goes beyond the possibilities of simulations to create a realistic and flexible test environment. The progress in unmanned aerial vehicles (UAV) and software defined radio (SDR) technologies obtained in the last years provide this efficient and flexible approach to mimic GNSS sat...    »