The GNSS receiver and simulator group is working on the institutes sophisticated software GNSS receiver MuSNAT. A GNSS software receiver is a complete GNSS receiver but performs all signal processing on generic computer instead of using a chip. A frontend is used to convert the analog GNSS signal into digital samples and thus to connect the computer to a GNSS antenna. We typically use the SX3 frontend from IFEN (https://www.ifen.com/products/sx3-gnss-software-receiver/), or frontends from National Instruments (http://www.ni.com/de-de/support/model.usrp-2955.html). More information about software receivers can be found in https://en.wikipedia.org/wiki/GNSS_software-defined_receiver.

MuSNAT stands for Multi Sensor Navigation Analysis Tool and complements conventional GNSS receiver functionality (acquisition, tracking, position computation) by

  • GNSS signal and channel analysis
  • Signal quality monitoring
  • GNSS receiver and navigation algorithm development
  • Integration with other navigation technologies such as INS or LiDAR (loose to ultra-tight coupling)
  • RTK and PPP.
  • Galileo signal authentication (OS-NMA)

 

New: By reverting the data flow inside the receiver, MuSNAT is also able to generate a full constellation GNSS-Signal with variable signal power and navigation message, which can then be broadcast using a digital-to-analog converter. MuSNAT realizes thus the GNSS-transceiver concept. This approach is presented at the ION-GNSS+ 2018 in Miami/Florida by D. Maier.

MuSNAT is developed as a Visual Studio 2017 C++/C# project making use of various acceleration techniques like Intel IPP and CUDA. The receiver (=MuSNAT-Core) is configured with an XML-File and started with a simple GUI.

Fig1_Screenshot_MuSNAT_Core.png

 Fig. 1: Screenshot of MuSNAT-Core

 

The MuSNAT-Core logs all GNSS related data including channel wise correlation or tracking loop data plus all sensor data into an SQL database. A dedicated graphical user interface (=MuSNAT-Analyzer) then allows to visualize all data in a time synchronous way to identify relationships between signal and senor data artefacts and positioning performance.

Fig2_Screenshot_MuSNAT_Analyzer.png

 Fig. 2: Screenshot of MuSNAT-Analyzer

 

MuSNAT supports all GNSS and all frequencies as well as inertial (gyro, accelerometer) and camera data. To read in IF samples, the standard developed by the Institute of Navigation is supported as described on http://sdr.ion.org. The software was tested with a maximum sample rate of 200 MHz and 12 separate GNSS frequency bands but is in principle unlimited. The processing speed is high and on a today’s desktop several hundreds of channels can be processed in real-time (see also: http://insidegnss.com/more-than-we-ever-dreamed-possible/).

With the help of MATLAB various processing results at signal processing, sensor data or PVT level can also be visualized. Very often acquisition and tracking log files give deeper insight into the GNSS signal processing.

Fig3_MATLAB_visualization_GalileoE1CBOC.png

Fig. 3: MATLAB visualization of Galileo E1 CBOC acquisition

 

Fig4_MATLAB_visualization_GalileoE1CBOC_multicorrelator.png

Fig. 4: MATLAB visualization of a Galileo E1 CBOC multi-correlator during tracking

 

With the help of the source code integrated RTKLIB (http://www.rtklib.com/) precise carrier phase positioning in RTK and PPP mode can be performed using the software receiver generated multi GNSS and multi frequency observations.