Network-Based Augmentation System (NBAS) Architectures Optimized to Support Urban Air Mobility (UAM)

Integrity-assured navigation is essential to support highly automated operation of Urban Air Mobility (UAM) at lower altitudes in urban or suburban area. This paper develops a Network-based Augmentation System (NBAS) architecture which utilize GNSS pseudorange corrections and monitoring information of reference stations installed at multiple vertiports to improve navigation accuracy and integrity. A new monitoring concept of enhancing detection capability for spatially-decorrelated errors is proposed by combining information of vertiports located farther from users. Simulations are conducted to compare the performance of the NBAS system to that of the conventional Ground-based Augmentation Systems (GBAS) architecture (i.e., single reference station) assuming the use of a dual-frequency and dual-constellation (GPS and Galileo) GNSS and the dual-frequency divergence-free smoothing method. Simulation results show a significant reduction in both ionosphere-induced and ephemeris-failure threats by utilizing the multiple monitor capability of networked ground stations and UAM vehicles.