A software implemented receiver for satellite based augmentation systems: an enhancement to global navigation satellite systems

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The global navigation satellite system GPS (Global Positioning System) offers a position accuracy of about 10-15 meters today. However, this is not enough for some applications such as navigating ships through narrow channels. Furthermore, GPS does not provide any integrity of the system (a maximum error bound of the position). Integrity is critical for safety-of- life applications, such as in the aviation industry. EGNOS (European Geostationary Navigation Overlay System) is a satellite based augmentation system in development, that together with GPS provides integrity and improved accuracy of the user position. EGNOS works by closely monitor the GPS satellites at monitoring stations scattered around Europe. Corrections and integrity bounds of the GPS signals are computed and encoded into messages. These messages are transferred to the users via geostationary satellites on the same frequency as GPS. This thesis describes a receiver implementation for decoding the EGNOS signal-in-space into messages and applying those messages to GPS measurements. Those steps are done in real-time. The EGNOS receiver is built as an extension to an existing GPS receiver. The EGNOS receiver decodes the signal-in-space into messages using a Viterbi decoder. These messages are then processed to compute local cor...