Broadband multi-frequency GNSS signal simulation with GPU

This work introduces an alternative architecture of a GNSS signal simulator, where the multiple GNSS services in the full GNSS bandwidth from L5 to L1 are generated and mixed in digital form. The digital-to-analog conversion and up-conversion to L-band is then applied to the single compounded wideband digital signal. The digital signal generation and mixing is implemented on a pair of strong GPUs with specially designed algorithms for massive parallel signal generation, mixing and quantization. Data transfer overlaps with the signal generation on both GPUs. The architecture uses up the full speed of the PCIe interface to transfer the signal to a broadband DAC-board and to reach high bandwidth for real-time generation. The digital part of the system was build up using low-cost mass-market components. The backbone of the system is a gaming PC system and two gaming-level graphic cards with total costs below 5000 €. The DAC conversion board and up-conversion need to reach high conversion rate and broad-band requirements, but it is only a single wide band channel to be processed without any inter-channel synchronization. The objective of the work was to reach real-time capability for a sufficient number of channels and GNSS signals to demonstrate viability of the concept. The potential and limits with respect to issues of signal quality, simulation settings flexibility and capacity to simulate important signal features were assessed as well.