Some examples disclosed herein include a method. The method may include determining a relationship between a property of a position, navigation, and timing (PNT)-based timing signal and a property of a virtual time source. The method may also include determining a state of the PNT-based timing signal at least partially responsive to the determined relationship. The method may also include one or more of: providing the PNT-based timing signal at least partially responsive to determining that the state of the PNT-based timing signal corresponds to a first state, disregarding the PNT-based timing signal at least partially responsive to determining that the state of the timing signal corresponds to a second state, and providing an indication of the state of the PNT-based timing signal at least partially responsive to determining that the state of the timing signal corresponds to a second state. Related devices, systems and methods are also disclosed.

A system, non-transitory computer readable medium, and method include entering redundant oscillators and a cascaded oscillator of a spoofing resistant system into an initialization state. All but one of the redundant oscillators are disciplined to a time-and-frequency external input into normal disciplining state with the remaining one of the redundant oscillators in a holdover state. When all but one of the redundant oscillators have reached the normal disciplining state, placing all but one of the redundant oscillators into the holdover state, disciplining the remaining one of the redundant oscillators to the time and frequency external input, and disciplining the cascaded oscillator to one of the all but one of the redundant oscillators now in the holdover state. When the remaining one of the redundant oscillators and the cascaded oscillator have reached the normal disciplining state, transitioning from an initialization stage to a steady state management stage.

An anechoic chamber and test system that is adapted for installation in or to a vehicle. The chamber includes an outer structure that is durable enough to withstand the effects of transportation. The anechoic chamber and test system may also include an inner faraday shield, a transmission antenna, and a controller that can introduce GNSS, alternative navigation signals, jamming, or spoofing signals into the anechoic chamber along with vehicle sensor signals. The controller is adapted to monitor a GNSS system's ability to resist the jamming or spoofing signals using, at least in part, the vehicle sensor signals.

A tracking loop and associated method for tracking a satellite signal in a GNSS receiver and for determining a line-of-sight (LOS) signal from a plurality of satellite signals received by the GNSS receiver from a satellite. One or more first correlators perform a correlation between a code signal derived from one of the received satellite signals and a plurality of corresponding replica code signals to determine a plurality of code correlation sums comprising a prompt code correlation sum, one or more early code correlation sums and one or more late code correlation sums. One or more second correlators correlate the plurality of code correlation sums with a plurality of replica carrier signals, each having a different Doppler frequency offset, to determine, for each of the plurality of code correlation sums, a set of correlation magnitudes at frequencies of the plurality of replica carrier signals. An LOS identification module identifies the LOS signal based on a signal propagation delay corresponding to one or more local maxima within the sets of correlation magnitudes.

A duplicate peak detector acquires and tracks a first correlation peak for a data sequence associated with a navigation satellite in a satellite navigation signal. During tracking of the first correlation peak, a second correlation peak is acquired and tracked for the same data sequence. Respective values of at least one tracking variable of the two correlation peaks are analyzed, and based on the analysis it is determined whether the first and second correlation peaks are associated with the same navigation signal or different navigation signals. If the first correlation peak and the second correlation peak are associated with the same navigation signal, tracking of one of the correlation peaks is discontinued.

A method, apparatus and computer readable storage medium are provided for determining whether or not GNSS navigation data are potentially manipulated. In the context of a method, GNSS reference data is received that represents one or more GNSS signals observed by a reference receiver at a reference position. The method also receives GNSS navigation data and determines, at least partially based on said GNSS reference data and the GNSS navigation data, a position estimate of said reference position. The method further includes determining, at least partially based on said reference position and the position estimate of said reference position, whether or not the GNSS navigation data are potentially manipulated.

A method, apparatus and computer readable storage medium are provided for determining whether or not GNSS navigation data are potentially manipulated. In the context of a method, GNSS reference data is received that represents one or more GNSS signals observed by a reference receiver at a reference position. The method also receives GNSS navigation data and determines, at least partially based on said GNSS reference data and the GNSS navigation data, a position estimate of said reference position. The method further includes determining, at least partially based on said reference position and the position estimate of said reference position, whether or not the GNSS navigation data are potentially manipulated.

A method and apparatus for improving signal reception in a radio signal receiver is provided. The method comprises: receiving a signal from one or more remote sources; determining movement of the receiver; obtaining first and second phasor sequences indicative of the determined movement of the receiver in first and second directions; generating a third phasor sequence based on a weighted combination of the first and second phasor sequences in accordance with the first and second directions; and providing a correlation signal using the third phasor sequence, wherein providing the correlation signal comprises correlating a local signal with the received signal, and combining at least one of the local signal, received signal, and the result of the correlation with the third phasor sequence, such that a signal received along the second direction is suppressed relative to a signal received along the first direction. A corresponding positioning system is also disclosed.

A method and apparatus for improving signal reception in a radio signal receiver is provided. The method comprises: receiving a signal from one or more remote sources; determining movement of the receiver; obtaining first and second phasor sequences indicative of the determined movement of the receiver in first and second directions; generating a third phasor sequence based on a weighted combination of the first and second phasor sequences in accordance with the first and second directions; and providing a correlation signal using the third phasor sequence, wherein providing the correlation signal comprises correlating a local signal with the received signal, and combining at least one of the local signal, received signal, and the result of the correlation with the third phasor sequence, such that a signal received along the second direction is suppressed relative to a signal received along the first direction. A corresponding positioning system is also disclosed.

A method of determining a location of a mobile device in the presence of a spoofing signal includes obtaining current position information associated with the mobile device, determining a Global Navigation Satellite System (GNSS) signal search window for acquiring GNSS signals associated with a satellite based on the current position information, searching a GNSS signal associated with the satellite based on the GNSS signal search window, and determining updated position information of the mobile device based on at least information of the GNSS signal associated with the satellite.