Modernization of the Global Navigation Satellite Systems: Issues of Compatibility and Interoperability Among Them

During recent years, the incremental need for accurate Global Navigation Satellite Systems (GNSSs) has led to rapidly growing changes in operational status and practical exploitation, including the United States' GPS, Russian GLONASS, European Union's Galileo, Chinese BeiDou, and Satellite Based Augmentation Systems (SBASs). This review examines the status of modernized GNSS including new satellites, civil signals, and monitoring stations, with focus on compatibility and interoperability among these systems. Compatibility ensures systems can operate separately or together without unacceptable interference, while interoperability enables better combined capabilities than single-system reliance. With all providers moving toward the International Terrestrial Reference Frame (ITRF) and improved international cooperation, users will experience full benefits of compatible and interoperable signals. This study is relevant to receiver manufacturers and space users seeking to leverage multi-constellation GNSS technology.