Simulating GNSS constellations - GPS, Galileo and SBAS

The development of GNSS (Global Navigation Satellite System) receivers, especially mass market receivers, have to face cost constraints. To reduce the time to market, and thus the costs, the usage of a GNSS signal simulation facility is one possibility. GNSS signal simulators provide an effective tool for simulating the behavior of satellite-based navigation systems. They have to model the real world as close as possible, taking satellite orbits, atmospheric effects, satellite clock errors, multipath effects, etc. into account. For testing purposes, the whole simulation has to be performed in real-time. Furthermore an emulated communication link for testing AGNSS requests is implemented in the simulation software. This paper describes the development of such a simulation facility, providing signals of GPS L1, Galileo L1 OS, and SBAS, which was accomplished within the project GAMMA, funded by the 6^th framework program of the European Union.