The Multi-output Advanced Signal Test Environment for Receivers (MASTER) is a unique and powerful hardware simulation tool for the test and quality assessment of global navigation satellite system (GNSS) receivers. It is a full constellation simulator, offering control over the satellite orbit definitions, a user-specified location or track, date and time as well as orbit and clock errors, ionosphere, troposphere, multipath and interference. The scenarios can be repeated several times with exactly the same parameters.
Schematic of MASTER
Typical applications are:
- Testing of Galileo and GPS receivers in a quasi realistic environment under controlled and repeatable conditions,
- advanced testing of specific multipath and interference mitigation techniques,
- testing of array antenna receivers with digital beam forming as well as for heading and attitude determination,
- testing of GBAS systems, and
- calibration of time receivers.
The system consists of two modified Spirent GSS7790 hardware simulators for the simultaneous simulation of GPS and Galileo constellations. It generates all GPS (L1, L2, L5) and Galileo (E1, E5, E6) satellite signals, which can be accessed at RF, IF, and baseband level, for each satellite individually. The user can select specific signal components such as data and pilot channel, navigation data or pseudo random noise (PRN) code. Additionally, interference signals can be generated by an external programmable signal generator and overlaid on the satellite navigation signals.
The “true” values, such as simulated pseudo range, position, Doppler effects, time, velocity, etc. are available for each satellite as data files, offering a straightforward comparison with the values measured by the equipment under test.
Another powerful feature of the system is its capability to use pre-processed data files for modulation of signal power, code and carrier delay of each generated signals with up to 100 Hz update rate. By using such files, multipath and scintillations are generated with external models in SW, which may then be loaded into the hardware simulation when being run. Some simple multipath models are already available directly in the simulator software. However, by using pre-processed data files, more realistic channel models can be applied e. g. the models which were derived from channel measurements conducted by the Institute.
The accessibility of the digital baseband signals is a unique feature of MASTER, which does not exist in standard Spirent simulators. It was implemented for simulation of multi-antenna receivers. The spatial information, i.e. the carrier phase shifts of the signals between the different antenna elements, can be encoded into the baseband signals in the form of complex coefficients by utilizing a digital processing matrix (“Wavefront Matrix”), developed at the Institute.
For differential applications, the two constellation simulators can be configured in such a way, that a reference station and a rover can be simultaneously simulated. If more than one reference station is required, e. g. for GBAS, the different stations and the rover are simulated in successive runs and the receiver data are recorded for post-processing.
MASTER is used almost daily for internal and external projects. It is also contracted by external customers.