GBAS with RAIM Based on the Constrained GLRT for Precision Landing Using Galileo and GPS

Global navigation satellite systems have made an important improvement since the first utilization for military purposes. One of the civil application domains that profit the most of this technology is the civil aviation. It is also the most challenging application due to the high level of safety required. One of the most stringent required parameter is the integrity of the position provided by the system and to fulfill this requirement, additional algorithms at system and at user level are necessary to provide robust information to the pilot. At the system level, the American Wide Area Augmentation System (WAAS) is the first augmented system that has been proposed to support civil aviation phases of flight. Unfortunately the availability of this system can provide only Approach with Vertical guidance I (APV I) requirements. At the user level, the consistency check algorithms for monitoring the integrity have been developed. These algorithms are known as Receiver Autonomous Integrity Monitoring (RAIM) algorithms. Conventional "snapshot" RAIM Fault Detection/Exclusion (FDE) algorithms based on least squares method consider epoch by epoch to check pseudo-ranges. Another approach considers the use of previous epochs to augment the number of observations and thus information. These algorithms are called sequential RAIM. Snapshot and sequential RAIM FDE based on the constrained Generalized Likelihood Ratio Test (GLRT) have shown very promising results for single and dual frequency absolute positioning receivers. Previous studies have demonstrated under certain circumstances that such a RAIMcould fulfill requirements of APV I. In this paper the detection/exclusion functions availability for three different RAIM FDE algorithms applied to the differential GPS and Galileo modes is discussed and some very preliminary results of simulation are shown