Global navigation satellite systems (GNSS) provide accurate positioning, navigation and timing anywhere on Earth. Several nations have developed their own systems. The most commonly used navigation satellite system is the Global Positioning System (GPS) provided for global use by the United States. The GLONASS system is the Russian counterpart of GPS. Other systems in development are the European Galileo and the Chinese BeiDou systems. The combined use of multiple GNSS offers many potential benefits, including improved availability, accuracy, reliability, and integrity. The use of software-defined GNSS receivers has been the focus of growing interest due to the ease of development of signal processing algorithms in software as compared to hardware. The software-defined GNSS receiver FGI-GSRx, which is used in this work, is a multi-constellation, multi-frequency software-defined receiver developed by the Finnish Geospatial Research Institute. It is a post-processing receiver developed in Matlab, currently capable of utilizing GPS, Galileo and BeiDou. This thesis presents implementation of a receiver software for the GLONASS satellite navigation system signal as part of the FGI-GSRx multi-constellation software-defined receiver. The implementation is limited to the GLONASS Standard Positioning Service signal on the L1 frequency. The implemented receiver is able to process digitized GLONASS signal samples and calculate a positioning solution. The work includes design, development, implementation, and verification of the receiver software.Verification results show that the receiver is able to acquire and track GLONASS signals and to use them to produce a combined GPS/GLONASS positioning solution. In addition, the receiver is used to test the impact of a GPS jammer on multi-GNSS positioning, showing results of the robustness benefits of adding multiple GNSS systems to into the positioning process.
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