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ABSTRACT:The GNSS environment is experiencing two major changes: the introduction of a new civil signal in the L5 band and the launch of new GNSS constellations. These improvements could enable worldwide vertical guidance using Advanced Receiver Autonomous Integrity Monitoring (ARAIM). Before ARAIM can be implemented, it will be necessary to develop a common understanding across service providers of the navigation requirements, the threat model, the airborne algorithm, and the role of ground monitoring. We outline a concept for the provision of integrity based on ARAIM. First, an interpretation of vertical guidance (LPV-200) requirements is proposed. Then, we describe a comprehensive threat model for GNSS which includes both nominal performance and faulted behavior. We will show how the threats could be mitigated through the use of ground monitoring and the Integrity Support Message in addition to the ARAIM airborne algorithm. Finally, examples of constellation configurations providing worldwide coverage of LPV-200 are presented.

One of the key approaches to monitor the integrity of Global Satellite Navigation Systems (GNSS) is receiver autonomous integrity monitoring (RAIM). Existing RAIM algorithms utilise two tests in the position domain (for RAIM availability) and measurement domain (for failure detection). This paper proposes an alternative RAIM algorithm, which is based entirely in the measurement domain. This algorithm can be used for sensitivity analyses to support performance specification and system design. It can also be used during actual flight operations where the trigger is the phase of flight and its required navigation performance (RNP) parameters. This is made possible by computationally efficient calculation of the chi-squared parameters. The algorithm reverts to the current approach if the phase of flight is unknown. Simulation results for non-precision approach (NPA) have been used to demonstrate the effectiveness of the proposed algorithm.

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