Accurate and reliable positioning solutions through multi-constellation and multi-sensor approaches

With the development of advanced driver assistance systems (ADAS) and autonomous vehicles (AV), recent years have seen an increasing evolution of on-board sensors and communication systems capable of interacting with available infrastructures, including satellite constellations and other systems that provide helpful information for the localization process. Therefore, it is essential to develop solutions that employ a multi-sensor approach to ensure accurate and reliable positioning in different navigation scenarios. This research proposes positioning solutions based on the Software-Defined Radio (SDR) paradigm, utilizing the Global Navigation Satellite System (GNSS). The approach is characterized by multi-constellation, multi-frequency, and augmented capabilities and can be enhanced by integrating with other sources of information. Moreover, exploring emerging technologies within the localization process contributes to creating more resilient and robust systems. In this context, this thesis investigates the implementation of services capable of timely receiving, decoding, and processing wireless signals. Two SDR-based case studies are presented: the first focused on positioning using ADS-B signals, and the other involved a distributed network designed to offer sensing and localization services supporting next-generation mobile networks. The thesis is structured into three main sections. The first section provides a theoretical background, with an extensive description of the technological aspects and critical issues involved. The second section includes the most relevant publications produced or presented during this doctoral program. Finally, the third section presents the conclusions and outlines directions for future research. Initially, a study on GNSS identifies the primary limitations and physical phenomena affecting the system. This analysis includes the development of SDR-based solutions capable of simulating and receiving GNSS signals. Detailed investigations identify the key factors influencing localization systems' accuracy, availability, continuity, and integrity. This examination involves a comparison of different SDR platforms through experimental activities conducted in controlled environments and scenarios involving the processing of real GNSS signals. Subsequently, alternative systems capable of providing sensing and positioning services are explored. Two approaches are considered: the SDR-based receiver calculates its position using information from mobile anchors, and another where distributed and synchronized anchors detect the transmitter or interference source. The first approach is addressed as opportunistic positioning using ADS-B signals, while the second approach deals with sensing and localization using an SDR-based distributed sensor network. This research also presents an architecture for navigation based on a multi-sensor approach. This architecture is implemented to develop an on-board unit (OBU) within the framework of the EMERGE project. This solution addresses the challenge of reducing GNSS system errors by utilizing augmentation services that provide atmospheric and clock corrections. Additionally, the process of sensor fusion using GNSS and inertial measurement data, as well as the results obtained from field tests, are presented.