Abstract: A practical method for adding new high-performance, tightly integrated Nav-Com capability to any Global Navigation Satellite System (GNSS) user equipment requires no hardware modifications to the existing user equipment. In one example, the iGPS concept is applied to a Defense Advanced GPS Receiver (DAGR) and combines Low Earth Orbiting (LEO) satellites, such as Iridium, with GPS or other GNSS systems to significantly improve the accuracy, integrity, and availability of Position, Navigation, and Timing (PNT) and to enable new communication enhancements made available by the synthesis of precisely coupled navigation and communication modes. To achieve time synchronization stability between the existing DAGR and a plug-in iGPS enhancement module, a special-purpose wideband reference signal is generated by the iGPS module and coupled to the DAGR via the existing antenna port.

Abstract: A practical method for adding significant new high-performance, tightly integrated Nav-Com capability to any Global Navigation Satellite System (GNSS) user equipment, such as GPS receivers, requires no hardware modifications to the existing user equipment. In one example, the iGPS concept is applied to a Defense Advanced GPS Receiver (DAGR) and combines Low Earth Orbiting (LEO) satellites, such as Iridium, with GPS or other GNSS systems to significantly improve the accuracy, integrity, and availability of Position, Navigation, and Timing (PNT)—in some cases by three orders of magnitude, to enable high precision GNSS carrier phase observable to be more readily exploited to improve PNT availability—even under interference conditions or occluded environments, and to enable new communication enhancements made available by the synthesis of precisely coupled navigation and communication modes.

Abstract: A method and apparatus for simulating radio-frequency Global Navigation Satellite System (GNSS) signals that are carrier-phase and code-phase aligned with ambient GNSS signals at a user-specified location in the vicinity of the simulator. Such phase alignment allows the synthesized signals to be made to appear substantially the same as the authentic signals to a target receiver, allowing the target receiver to transition seamlessly between authentic and simulated signals. The method is embodied in a device, a phase-coherent GNSS signal simulator, which can be implemented on a digital signal processor for embedded applications.

Abstract: A method of countering GNSS signal spoofing includes monitoring a plurality of GNSS signals received from a plurality of GNSS signal sources and comparing broadcast data to identify outlying data, which is excluded from generation of a navigation solution defined by the plurality of GNSS signals. The outlying data can be a vestigial signal from a code or carrier Doppler shift frequency. The method includes triggering a spoofing indicator upon identification of the outlying data or other phenomenon. The phenomenon can include a shift in a phase of a measured GNSS navigation data bit sequence or a profile phenomenon of a correlation function resulting from correlation of the incoming GNSS signals with a local signal replica. The profile phenomenon can be the presence of multiple sustained correlation peaks. A nullifying signal can be generated and superimposed over a compromised signal.

Abstract: A method for upgrading GNSS equipment to improve position, velocity and time (PVT) accuracy, increase PVT robustness in weak-signal or jammed environments and protect against counterfeit GNSS signals (spoofing). A GNSS Assimilator couples to an RF input of existing GNSS equipment, e.g., a GPS receiver, and extracts navigation and timing information from available RF signals, including non-GNSS signals, or direct baseband aiding, e.g., from an inertial navigation system, frequency reference, or GNSS user. The Assimilator fuses the diverse navigation and timing information to embed a PVT solution in synthesized GNSS signals provided to a GNSS receiver RF input. The code and carrier phases of the synthesized GNSS signals are aligned with those of actual GNSS signals to appear the same at the target receiver input. The Assimilator protects against spoofing by continuously scanning incoming GNSS signals for signs of spoofing, and mitigating spoofing effects in the synthesized GNSS signals.