is currently a PhD student at ENAC. He has obtained telecommunication engineer diploma in 2014 and a Master of Science in wireless communication in 2016 at Politecnico di Torino, Italy. He is currently studying signal processing algorithms and integrity monitoring techniques adapted to the navigation in urban areas. His thesis is funded by ABBIA GNSS Technologies.
International standards require the use of a weighted least-squares approach to onboard Receiver Autonomous Integrity Monitoring (RAIM). However, the protection levels developed to determine if the conditions exist to perform a measurement check (i.e. failure detection) are not specified. Various methods for the computation of protection levels exist. However, they are essentially approximations to the complex problem of computing the worst-case missed detection probability under a weighted system. In this paper, a novel approach to determine this probability at the worst-case measurement bias is presented. The missed detection probabilities are then iteratively solved against the integrity risk requirement in order to derive an optimal protection level for the operation. It is shown that the new method improves availability by more than 30% compared to the baseline weighted RAIM algorithm.
The level of safety to be expected from global positioning system (GPS) must be known in order to use it to support safety critical operations such as air navigation. This is captured by the navigation performance parameter of integrity which includes the ability of the navigation system to deliver a warning to the user in the event of a significant failure and within a specified time-to-alert. Given the high percentile requirement associated with integrity, assessment of expected system performance both in the nominal case and during failure events, requires the application of analytical techniques. This paper identifies the weaknesses of the current methods for assessing the level of performance to be expected of GPS for non-precision approaches and proposes ways to address them including a novel application of a mathematical integration technique that greatly reduces the computational load associated with integrity performance calculations. Results based on computation times show that the new method reduces computational load by a factor of 500? with a high accuracy and associated high level of confidence. It is shown that in some cases, the technique presented is able to improve GPS RAIM availability beyond the gains achieved by measurement weighting.
This paper proposes a new dual-frequency signal deformation fault monitor which can effectively reduce the time delay at the Ground-Based Augmentation System (GBAS) airborne user from the airborne filter initialization to the time when it incorporates ground corrections and user measurements for navigation, assuring the system integrity at the same time. The new monitor is applied together with the existing Honeywell signal deformation monitor and Code-Carrier Divergence monitors to protect the airborne users against the signal deformation faults. In addition, the probability of missed detection of the monitors are assessed for the GBAS Approach Service Types (GAST) F, which supports the Category (CAT) II and III precision approaches based on the multi-frequency and multi-constellation. As a result, the proposed monitor together with the Honeywell and the CCD monitors is able to assure the system integrity for all fault cases within the threat space. The result also shows that the addition of the proposed monitor can reduce the time delay by 80% and moreover, it can even reduce the recommended time delay below 50 second. Consequently, it can avoid the unnecessary delays for the use of newly available satellites at the airborne.
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