Dynamic Reconfiguration in a GNSS Software Defined Radio for Multi-Constellation Operation

Recent advances in the US GPS constellation have resulted in additional signals being made available for both military and civil applications. The modernized GPS signal structure now includes signals broadcast on three frequencies with both the legacy GPS modulation codes, additional civilian codes, and also additional military codes on L1 and L2. In the next few years, GNSS users will also be able to access increasing numbers of new signals from other satellite constellations, including the European Galileo, the Russian Global Navigation Satellite System (GLONASS), the Japanese Quasi-Zenith Satellite System (QZSS), the Indian GPS Aided Geo Augmented Navigation (GAGAN) and the Chinese Compass Navigation Satellite System. Historically, GNSS receivers have been designed with dedicated channels each capable of tracking only a single satellite code. As the number of codes and frequencies increase, the demands on a conventional GPS receiver get higher. Moreover, to track the different signals broadcast by other GNSS satellite systems, even more channels would be required to be set up to track their new codes. The increase in the number of channels using a conventional receiver design would also result in increased device size and correspondingly higher power operation. In this paper, we describe a GNSS Software Define Radio (SDR) architecture that allows for dynamic reconfiguration of the SDR channel resources to track different GNSS satellite codes and frequencies. With this approach, the flexibility of the SDR can be leveraged to implement a full-function GNSS receiver capable of leveraging any of the GNSS signals without requiring massive numbers of parallel channels to operate.