Test of GBAS integrity monitoring system using GPS simulator

Abstract

In recent years, many countries are developing aircraft navigation systems using GNSS(Global Navigation Satellite System), because GNSS has many technical and economic benefits. International organizations as ICAO(International Civil Aviation Organization) and RTCA(Radio Technical Commission for Aeronautics) set up international standards of GBAS(Ground Based Augmentation System) using GNSS and recommend countries to develop GBAS that is based on the standards. To go with the international stream, Korea Airport Cooperation has also developed GBAS. For evaluating the system, KAC and Seoul National University have performed flight tests of the developed GBAS several times and have concluded that the system has good accuracy enough to be used in aircrafts. At that time, the purpose of tests was focused on accuracy of GBAS. But integrity of the system which is important for safety of aircrafts was not tested sufficiently, because it is impossible to make erroneous situations of real GPS signals. So, at this time, we used GPS simulator which can generate GPS signals with satellite failure scenarios. The GPS simulator used in this test generates GPS signals by the scenarios organized in advance. The scenarios can include pseudorange and carrier phase error, parity error and etc. So we organized several scenarios which can includes potential errors of GPS signals and many possible cases for testing the system effectively and accurately. And we tested integrity function of the GBAS system by using GPS signals generated by the simulator. This paper introduces the implemented integrity monitoring system and algorithms used in the tests. And it describes the scenarios of satellite failure. Finally, this paper shows the results of tests.