GNSS integrity for aviation and road user applications

The evolution of Global Navigation Satellite System (GNSS) is paving the way for new satellite constellations and civil signals. Currently, the European Galileo and Chinese BeiDou are in deployment phases, while the American GPS and Russian GLONASS are going through modernization. On completion, satellite navigation users are expected to receive a large number of ranging signals on two civil frequencies instead of one. These significant improvements open up new possibilities to extend the use of satellite navigation for worldwide vertical guidance of aircraft down to 200 ft. above ground level. GNSS Evolutionary Architecture Study (GEAS) panel proposed several candidate integrity architectures for worldwide vertical guidance of aircraft. Among the candidate integrity architectures, Advanced Receiver Autonomous Integrity Monitoring (ARAIM), which is an extension of single frequency and lateral guidance-only RAIM, is expected to utilize minimal infrastructure in the provision of vertically guided approach down to Localizer Performance with Vertical guidance at a decision altitude of 200 ft. above ground level or LPV-200. The first contribution of this thesis is to analyze worldwide availability of Advanced RAIM for the provision of LPV-200 approach procedure. In this regard, ARAIM availability is evaluated using MATLAB Algorithm Availability Simulation Tool (MAAST) considering single and multiple GNSS constellations including GPS, Galileo, GLONASS and BeiDou. Furthermore, several Signal In Space (SIS) error characterizations and multiple satellite and constellation failures are taken into account during the analysis of ARAIM availability. Advanced RAIM user algorithm relies on external information in providing real-time integrity monitoring on board aircraft. This external information would be disseminated by ground station in the form of Integrity Support Message (ISM). Unlike Satellite Based Augmentation System (SBAS), Advanced RAIM does not require a realtime communication channel for the dissemination of ISM, thanks to the distribution of integrity burden between the airborne receiver, ground monitoring network, and core constellation service providers. This distribution of integrity burden using ARAIM concept opens up new possibilities to investigate various channels for dissemination of ISM to the aircraft. In this framework, this thesis analyzes Terrestrial Trunked Radio (TETRA) for the dissemination of ISM to the State Aircraft. A State Aircraft is defined as an aircraft used for the customs, military, and police services. TETRA Air-Ground-Air operation supported by aeronautical base station presents an attractive solution for the dissemination of ISM to the State Aircraft. The analysis of TETRA for the dissemination of ISM to the State Aircraft is based on average and maximum end-to-end ISM dissemination latency considering a variety of parameters that directly impacts the end-to-end ISM dissemination latency, which include different ISM contents, ISM formats, ISM update intervals, channel Bit Error Rate (BER), and different number of users. Research on ARAIM is still evolving while the current research is focused on Advanced RAIM system architecture. This thesis contributes to on going discussion on Advanced RAIM architecture by outlining the system architecture. Furthermore, this thesis proposes three-tiers integrity monitoring strategy, which is the extension of multiple ISM Advanced RAIM architecture for the worldwide vertical guidance of aircraft. The three-tiers integrity monitoring strategy uses distinct SIS error bounding methodology within each tier and provides ground validated extended ephemerides within tier-1 and ephemerides with improved accuracy within tier-2 using TETRA network. The three-tiers strategy, on one hand, protects the airborne receiver against the threat of constellation wide faults, while on the other, it makes use of the TETRA Air-Ground-Air technological solution that allows the dissemination of ISM to the State Aircraft over a wide coverage area and at higher altitude. GNSS integrity monitoring is the key enabler of Safety of Life (SoL) applications relying on the use of satellite navigation such as aviation. However, integrity monitoring of GNSS is not limited to applications that involve life safety but also plays a key role in enabling applications in which positioning errors may have legal or economic consequences. Such applications are known as liability-critical applications to distinguish it from safety-critical applications. The existing integrity paradigms are mainly developed for aviation considering the International Civil Aviation Organization (ICAO) performance requirements and are meeting the Required Navigation Performance (RNP). The "as is" application of existing integrity concept in the urban and road user environment does not satisfies the integrity and more importantly the navigation system availability requirements. One of the reasons is the mismatch of the pseudorange error estimation model and the urban environment. This thesis contributes in evaluating the performance of a novel method of pseudorange error estimation that does not rely on the theoretical and/or empirical models but considers the environment surrounding the user. Another issue that is considered in this thesis is the impact of solar radio burst on the performance of GNSS receivers. Solar radio burst is the sudden outburst of radio noise from the Sun, which decreases C/N0 of every tracked satellite signal by increasing the noise floor of GNSS receiver. The degradation in C/N0 due to the solar radio frequency interference can result in degraded navigation accuracy or complete loss of receiver tracking. This could be an issue for wide range of applications that demand uninterrupted satellite navigation service with certain level of accuracy, particularly for the Safety of Life (SoL) applications relying on the use of GNSS, for instance, aircraft landing procedures in civil aviation. Finally, this thesis analyses the performance of large subset of GPS receiver including aviation and survey grade receivers located worldwide. The performance assessment includes estimation of GPS L1/L2 C/N0 degradation and rise in horizontal and vertical positioning error during the September 24, 2011 solar radio burst event.