A New Improved RAIM Method Based on the Optimally Weighted Average Solution (OWAS) Under the Assumption of a Single Fault

摘要

Until recently all Receiver Autonomous Integrity Monitoring (RAIM) methods have been devised to provide integrity for en route through nonprecision approach phases of flight under the assumption of up to a single fault at a time. For RAIM, availability has always been a critical issue, and achieving higher availability always the goal. A recently proposed RAIM method called NIORAIM achieves higher availability than conventional RAIM methods by applying weights to the range measurements. More recently, a method named Optimally Weighted Average Solution (OWAS) was proposed, which again improves availability but by applying weights in the position domain. This OWAS method was devised to provide integrity monitoring in the presence of a common mode fault affecting multiple satellites in case two independent constellations are available to the user. This paper presents another OWAS-based RAIM method but working with a single constellation. This new method is similar to NIORAIM in that it assumes a single fault at a time and can achieve higher availability than conventional methods, using a weighting concept. The difference is that NIORAIM applies numerically derived weights to the range measurements, while both OWAS methods use weights analytically derived in the position domain. The availability of this new OWAS method is evaluated and compared with a similar previously developed conventional method. While side-by-side comparison of availability between this method and NIORAIM under exactly the same set of conditions could not be made, they appear to have similar availability.