Analyzing RAIM performance for an MEO/GEO hybrid GNSS constellation

MEO/GEO hybrid constellation is employed in some GNSS systems such as BeiDou. With the increased number of satellite vehicles in view and strengthened geometry, positioning performance (accuracy, integrity and availability) is to be significantly improved. In this research, a number of performance analyses have been conducted regarding the key parameters, including minimum detectable bias (MDB), external reliability and protecting levels in integrity. Both MEO/GEO hybrid constellation and MEO only constellation are evaluated for comparison. Conclusion can be drawn from the test results that, the introduction of GEO satellites in addition to the traditional constellation has great benefits of improved performances, not only the positioning accuracy and availability, but also the integrity. With the help of geostationary satellites in the hybrid constellation, RAIM performance has been significantly improved. MDB values for all the satellites are decrease, e.g., from 7.8m down to 4.9m.