GNSS Software Defined Radio: History, Current Developments, and Standardization Efforts

Taking the work conducted by the Global Navigation Satellite System (GNSS) Software Defined Radio (SDR) working group during the last decade as a seed, this contribution summarizes for the first time the history of GNSS SDR development. It highlights selected SDR implementations and achievements that are available to the public or influenced the general SDR development. The relation to the standardization process of Intermediate Frequency (IF) sample data and metadata is discussed, and a recent update of the Institute of Navigation (ION) SDR standard is recapitulated. The work focuses on GNSS SDR implementations on general purpose processors and leaves aside developments conducted on Field Programmable Gate Array (FPGA) and Application-Specific Integrated Circuits (ASICs) platforms. Data collection systems (i.e., front-ends) have always been of paramount importance for GNSS SDRs and are thus partly covered in this work. The work represents the knowledge of the authors but is not meant as a complete description of SDR history. Part of the authors plan to coordinate a more extensive work on this topic in the near future.