Towards secure & robust PNT for automated systems

This dissertation makes four contributions in support of secure and robust position, navigation, and timing (PNT) for automated systems. The first two relate to PNT security while the latter two address robust positioning for automated ground vehicles. The first contribution is a fundamental theory for provably-secure clock synchronization between two agents in a distributed automated system. All one-way synchronization protocols, such as those based on the Global Positioning System (GPS) and other Global Navigation Satellite Systems (GNSS), are shown to be vulnerable to man-in-the-middle delay attacks. This contribution is the first to identify the necessary and sufficient conditions for provably secure clock synchronization. The second contribution, also related to PNT security, is a three-year study of the world-wide GPS interference landscape based on data from a dual-frequency GNSS receiver operating continuously on the International Space Station (ISS). This work is the first publicly-reported space-based survey of GNSS interference, and unveils previously-unreported GNSS interference activity. The third contribution is a novel ground vehicle positioning technique that is robust to GNSS signal blockage, poor lighting conditions, and adverse weather events such as heavy rain and dense fog. The technique relies on sensors that are commonly available on automated vehicles and are insensitive to lighting and inclement weather: automotive radar, low-cost inertial measurement units (IMUs), and GNSS. Remarkably, it is shown that, given a prior radar map, the proposed technique operating on data from off-the-shelf all-weather automotive sensors can maintain sub-50-cm horizontal position accuracy during 60 min of GNSS-denied driving in downtown Austin, TX. This dissertation’s final contribution is an analysis and demonstration of the feasibility of crowd-sourced digital mapping for automated vehicles. Localization techniques, such as the one described in the previous contribution, rely on such digital maps for accuracy and robustness. A key enabler for large-scale up-to-date maps is enlisting the help of the very consumer vehicles that need the map to build and update it. A method for fusing multi-session vision data into a unified digital map is developed. The asymptotic limit of such a map’s globally-referenced position accuracy is explored for the case in which the mapping agents rely on low-cost GNSS receivers performing standard code-phase-based navigation. Experimental validation along a semi-urban route shows that low-cost consumer vehicles incrementally tighten the accuracy of the jointly-optimized digital map over time enough to support sub-lane-level positioning in a global frame of reference.Electrical and Computer Engineerin

Assessment of Dual-frequency Signal Quality Monitor to Support CAT II/III GBAS

International audienceThis paper assesses the performance of the signal quality monitors for the Ground-Based Augmentation System (GBAS) which supports Category (CAT) II and III precision approach. Three types of monitors are used for signal deformation faults: Honeywell signal quality monitor (SQM), ENAC Code-Carrier Divergence (CCD) monitor and a proposed Divergence-Free (DF)-Innovation monitor. The existing Honeywell SQM and ENAC CCD monitors have some response time due to the smoothing filter used for their metrics. Consequently, the performance of those monitors is limited right after the fault onset. To improve the monitor performance in this time period, the DF-Innovation monitor has been proposed. The performance of the monitors has been assessed by comparing the minimum value of the probabilities of missed detection of three monitors and the required probability of missed detection according to the differential range error, which is defined in the standard document. As a result, for GBAS Approach Service Types (GAST) F, the probability of missed detection of the monitor was compliant with respect to the requirements for all fault cases and receiver configurations, for GPS L1/L5 and Galileo E1/E5. In addition, we observed that the proposed DF-Innovation monitor is effective in reducing time delay, which is the required time at airborne from filter initialization time to the time when the airborne user incorporates the measurement and correction for navigation. To be more specific, the use of the proposed monitor can reduce the time delay by 80% compared to the case without using the proposed monitor, and moreover, it can even reduce the value of time delay below 50 second, which is the recommended value currently