Provided are systems, methods, and devices for identifying correct satellite signals to improve the accuracy of a satellite navigation system. In some embodiments, identifying correct satellite signals may include receiving a plurality of satellite signals; demodulating the satellite signals to extract a first plurality of parameters; determining a first subset of parameters from the first plurality of parameters, wherein the first subset of parameters is based on a first geographic location; determining a second subset of parameters from a second plurality of parameters outside the first subset, the second plurality of parameters comprising one or more parameters of the first plurality of parameters outside the first subset, wherein the second subset of parameters is based on a second geographic location; and identifying an exemplary subset from the first subset and the second subset, wherein the exemplary subset comprises parameters corresponding to correct satellite signals.

A method of receiving two chip-by-chip multiplexed CSK signals (e.g., GNSS signals) and searching for a non-CSK signal with optimal performance at a given digit capacity of a sampling memory resided in parallel correlators. For CSK signals Prompt, Early and Late results for each of possible code shift are calculated as different sums of four punctured convolutions. Depending on configuration, the method allows to receive both multiplexed CSK signals with lesser quality or one of the CSK signals with better quality. The method can be implemented as an apparatus with four punctured correlators, a set of multipliers by 1 or 2.sup.N, another set of multipliers by 1 or 0, summers of four input to one result, a RAM, searchers of maximum, and conditional commutators.

A system network and methods supported by a constellation of GNSS satellites orbiting around the Earth, and deployed for precise remote monitoring of the spatial displacement, distortion and/or deformation of stationary and/or mobile systems, including buildings, bridges, and roadways. The methods involve (i) embodying multiple GNSS rovers within the boundary of the stationary and/or mobile system being monitored by the GNSS system network, (ii) receiving GNSS signals transmitted from GNSS satellites orbiting the Earth, and (iii) determining the geo-location and time-stamp of each GNSS rover while the stationary and/or mobile system is being monitored for spatial displacement, distortion and/or deformation, using GNSS-based rover data processing methods practiced aboard the system, or remotely within the application and database servers of the data center of the GNSS system network. The GNSS rovers also include on-board instrumentation for sensing and measuring the depth of water ponding about the GNSS rovers.

Techniques are provided for non-linear satellite state modeling. First global navigation satellite systems (GNSS) signal data is obtained from a set of GNSS satellites. First satellite state data is obtained. The first satellite state data includes orbit data for the set of GNSS satellites. A non-linear satellite state model that includes a plurality of model parameters is generated. The non-linear satellite state model is generated by adjusting the plurality of model parameters based on the first GNSS signal data and the first satellite state data. The non-linear satellite state model outputs satellite state data based on GNSS signal data. Second GNSS signal data is obtained from the set of GNSS satellites. A set of updated satellite state data is calculated using the non-linear satellite state model and the second GNSS signal data.

A method and apparatus detects and estimates geo-observables of navigation signals employing civil formats with repeating baseband signal components, i.e., “pilot signals,” including true GNSS signals generated by satellite vehicles (SV’s) or ground beacons (pseudolites), and malicious GNSS signals, e.g., spoofers and repeaters. Multi-subband symbol-rate synchronous channelization can exploit the full substantive bandwidth of the GNSS signals with managed complexity in each subband. Spatial/polarization receivers can be provided to remove interference and geolocate non-GNSS jamming sources, as well as targeted GNSS spoofers that emulate GNSS signals. This can provide time-to-first-fix (TTFF) over much smaller time intervals than existing GNSS methods; can operate in the presence of signals with much wider disparity in received power than existing techniques; and can operate in the presence of arbitrary multipath

A computer-implemented method is for detecting Global Navigation Satellite System (GNSS) signal spoofing. The method includes storing sample sequences of the predictable part and of the unpredictable part of a GNSS signal at a GNSS receiver. The predictable part includes predictable bits and the unpredictable part includes unpredictable bits. The value of the unpredictable bits from which the unpredictable sample sequences are extracted is verified. A first and a second partial correlation between the unpredictable, respectively predictable, sample sequences and a locally stored GNSS signal replica are computed. A predefined metric from the complex valued partial correlations is calculated. The predefined metric is compared with a predefined threshold value. In a zero-delay replay attack, the spoofer estimates the unpredictable bits introduced by a GNSS authentication protocol and introduces distortion into the signal. Detecting this distortion indicates whether the signal under analysis is being spoofed or is authentic.

An apparatus that performs spoof detection of satellite signals based on clock information derived from the satellite signals. The apparatus may include a position, velocity, time (PVT) component that derives the clock information from the satellite signals and provides the clock information to a spoof detection mechanism. In some embodiments, the clock frequency estimate is modeled as a Wiener process.

In conditions in which Global Navigation Satellite System (GNSS) signal spoofing is likely occurring, a GNSS receiver may be operated in a reduced operational state with respect to one or more GNSS bands that are likely being spoofed. According to embodiments, a reduced operational state with regard to a GNSS band may comprise performing one or more of the following functions with respect to that GNSS band: disabling data demodulation and decoding, disabling time setting (e.g., time of week (TOW), week number, etc.) disabling acquisition of unknown/not visible satellites, disabling satellite differences, disabling error recovery, reducing non-coherent integration time, and duty cycling the power for one or more receiver blocks associated with the GNSS band.

In accordance with an embodiment, a system includes a phase-locked loop (PLL) configured to provide a first local oscillator (LO) signal and a voltage-controlled oscillator (VCO) signal; a first quadrature demodulator configured to downconvert global navigation satellite system signals to produce a first intermediate frequency (IF) signal; a first signal processing chain configured to pass the first IF signal; a second signal processing chain comprising a first frequency divider configured to produce a second LO signal based on the first LO signal, and a second quadrature demodulator configured to convert the first IF signal to a second IF signal using the second LO signal; and a third signal processing chain comprising a second frequency divider configured to produce a third LO signal based on the VCO signal, and a third quadrature demodulator configured to convert the first IF signal to a third IF signal using the third LO signal.

Described herein is a method for improving the reception of a satellite navigation message divided in several pages and transmitted by one or several satellites. A satellite navigation message M of k pages is encoded inn pages, and any k retrieved pages from any satellite enables decoding of the original satellite navigation message M. An implementation of the method uses parallel block encoding for a binary erasure channel with high parity and zero overhead, where symbols at a fixed position of all pages are encoded in parallel into shorter codes. This method achieves full page interchangeability in the message transmission, optimizes message reception and reduces decoding cost.