Evaluating the model of multi : Global Navigation Satellite Systems (GNSS) constellation to mitigate the multipath signals

Abstract

The Global Navigation Satellite Systems (GNSS) are evolving continuously and are being used in many applications across the world. The GNSS is used in electrical industries, the banking sector, the agricultural sector, the transportation and logistics sectors, etc. The architecture and operation of the GNSS is made up of three subdivisions: the space section, control section, and user section. The space segment consists of the satellite constellation to generate and emit the GNSS code phase and carrier phase signals. The space segment further stores and broadcasts the navigation data that is uploaded to the system by the GNSS controllers. For accurate Position, Velocity and Time (PVT), the satellite constellation must have at least three or four satellites visible to the GNSS receiver. The control segment is also known as the ground segment and is accountable for the complete operations of the GNSS. The ground segment further controls and preserves the conformation files of the satellite constellation, updates the navigation data to all satellites, controls the atomic clock of the GNS, and predicts the satellite ephemeris. The user segment is made up of GNSS receivers; their purpose is to receive the GNSS signal that contains the code phase and carrier phase to determine the pseudorange and other observables. There numerous issues that obstruct the application of the GNSS across all sectors mentioned above; those are signal attenuation in the satellite channels, signal diffraction, and signal multipath. Hence, this thesis focused on mitigating the GNSS multipath signal by investigating the concept of Combined Signal Detection (CSD). The purposes was to reduce the impact of signal degradation and further enable the GNSS receivers to withstand the signal degradation in deep rural areas. There are numerous existing methodologies to mitigate multipath signal and improve the positioning, velocity and timing in urban areas. However, the proposed CSD approach provided the better performance by using the vector detection of all visible satellites to improve (DP) Direct Positioning , High Sensitivity (HS) and clock bias. Furthermore, the capabilities of the Global Positioning Systems (GPS) and Galileo satellites are integrated to accommodate the adoption of CSD concept. The CSD concept require the GNSS receiver that is capable of processing multi-frequencies. The multi-constellation GNSS receiver use numerous satellites that are in space, such as Global Positioning Systems (GPS) satellites, BeiDou satellites, Galileo satellites, and Glonass satellites. However, the similarities between the constellations is investigated before the system is integrated for multi-constellation. The concept of CSD proved to be capable of mitigating the signal multipath without introducing an external device or circuit. This thesis further provided the comprehensive analysis of sources that contribute towards the signal degradation