Implementation of GPS L1C in an Open-Source Software-Defined Receiver

The GPS L1C signal created as part of an on-going GPS modernization effort utilizes various signal structures including tiered ranging codes, a dedicated pilot channel, time-multiplexed BOC modulation, and new CNAV-2 navigation message with BCH and LDPC forward error correction. The paper aims to address the needs of GNSS researchers for new receiver tools that can utilize the new signal. A complete GPS L1C receiver was implemented for an open-source FGI-GSRx multi-GNSS software receiver developed at the Finnish Geospatial Research Institute (FGI). Receiver operation was validated using live and simulated IQ and CNAV-2 symbol data. The conducted tests demonstrated that the positioning precision of the implementation is well in line with theoretical expectations for code based positioning. The implemented GPS L1C capabilities will be made publicly available and the updated open-source FGI-GSRx receiver version will enable the use of the new GPS L1C signal in research and applications.