The GATE test bed cornerstones are eight ground transmitters, emitting the Galileo signals into the test area in the region of Berchtesgaden (Germany). Two monitoring stations located within the test area are receiving and processing these signals. A central processing facility which is the core of GATE is steering and controlling the signals transmitted. These Galileo signals are fully compliant to the Galileo OS ICD specification. With the GATE "Virtual Satellite Mode" a realistic moving Galileo satellite constellation can be simulated, supporting commercial Galileo receivers without any modification. Furthermore, the integration of additional sensors like odometer or inertial sensors allows testing of sophisticated integrated navigation systems and applications under realistic environmental and dynamic conditions, e.g. including multipath and interference effects. The four Galileo IOV satellites available from 2012 onwards can be used in combination with the eight GATE "satellites", enabling up to twelve visible Galileo satellites, thus reflecting a complete Galileo FOC constellation. With full control over the eight GATE "Galileo satellites", feared events can be simulated enabling evaluation of new user integrity (RAIM) algorithmic concepts and implementations.