Research On RAIM Algorithm Under The Assumption Of Simultaneous Multiple Satellites Faults

The advantage of the Global Navigation Satellite System(GNSS) has revolutionized the field of navigation for civilian aviation applications over the past three decades. GPS receiver has been used successfully from the en-route into the precision approach(PA). In the future, there will be many more navigation satellites(Galileo, a renewed GLONASS constellation, Compass), all expected to have signals in at least two frequencies. This has raised the possibility of using Receiver autonomous integrity monitoring(RAIM) for much more demanding phases of flight. However, the prior probability of failures could be larger than what is used now. With the fact that there will be many more ranging sources, it's necessary to consider the possibility of multiple failures.Beginning with the introduction of development of navigation system integrity monitoring technology and research status, in this paper, RAIM algorithm including Protection Level calculation methods and Fault Detection and Elimination methods are overviewed. There are several RAIM algorithms treating multiple failures. However, most of them present certain disadvantages: either the calculations required to compute the PL are very complex, or the link between these Protection Levels and the Probability of Hazardously Misleading Information is problematic. A traditional RAIM algorithm-Slope based, theoretical analysis shows that consideration of the multiple failures will decrease the availability. Multiple Hypothesis Solution Separation(MHSS) RAIM algorithm as an Aircraft-Based Augmentation System(ABAS) which can efficiently take advantage of the capabilities of future multiple constellation and multiple failures in order to provide an error protection level for the user. Due to the characters of low fault recognition rate and long computational time which FDE method base on MHSS. the FDE method is improved to achieve better detection and elimination rate. All of the methods are validated by simulation date.