A Real-time OSNMA-ready Software Receiver

To meet the growing need of robustness required in many civil navigation applications, both GPS and Galileo are proposing evolutions of their legacy signals, embedding features of authentication. The term authentication is intended as the ability of the system to guarantee to the users that they are utilizing non-counterfeit navigation data that comes from one of the constellation satellites. In particular, Galileo is introducing a new service, referred to as Open Service Navigation Message Authentication (OSNMA), designed to be disseminated on the E1 Galileo band. The new signal, whose transmission is expected to begin soon, will be fully backward compatible: in fact, the performance of not participant users, i.e.: those not capable or interested in processing the authentication bits, will not be affected. On the other hand, users willing to exploit the authentication service need to upgrade current Galileo receivers with a module able to process the OSNMA bits and verify the authenticity of the transmitted source. The paper describes the implementation of the software routines able to make a real-time GPS/Galileo fully software receiver ready for the reception and elaboration of the OSNMA service. Together with the description of the development work, the paper will provide some recommendations for the implementation, supported by detailed results from the code profiling analysis.