Abstract: The present disclosure provides an authentication method for a satellite-based navigation system that in some implementations includes: obtaining, by an authentication server, a plurality of message authentication bundles from a plurality of reference receiver stations, each message authentication bundle comprising at least one hash for authenticating a corresponding SNS message received by a respective reference receiver station from at least one satellite of the SNS; inserting, by the authentication server at least a subset of the hashes of the obtained message authentication bundles into a probabilistic data structure (PDS), which forms at least a part of a validation filter for authenticating a corresponding subset of SNS messages; and distributing the validation filter to at least one receiver-side device.

Abstract: A static GNSS receiver, a base station module, a method of estimating a position of a static GNSS receiver, and an associated computer program are provided. An example method includes calculating a first difference between a first pseudorange and a second pseudorange, each made at a first time. A second difference between a third pseudorange and a fourth pseudorange, each made at a second time, is calculated, with the second time different to the first time. A position of the GNSS receiver is calculated based at least in part on the accumulated pseudorange differences.

Abstract: A method and apparatus are provided for processing GNSS measurements to infer state information. An example method includes obtaining one or more residual error models for the plurality of GNSS measurements. The one or more residual error models describe a probability distribution of errors in each of the GNSS measurements. The method further includes inferring the state information based on the one or more residual error models. The GNSS measurements include at least one carrier phase measurement. The residual error model for the at least one carrier phase measurement is cyclic, such that errors in carrier phase that are separated by an integer number of cycles are regarded as equivalent. The probability distribution for the at least one carrier phase measurement comprises a function having a continuous first derivative, for example, a continuous first derivative at a phase boundary between successive cycles.

Abstract: A static GNSS receiver, a base station module, a method of estimating a position of a static GNSS receiver, and an associated computer program are provided. An example method includes calculating a first difference between a first pseudorange and a second pseudorange, each made at a first time. A second difference between a third pseudorange and a fourth pseudorange, each made at a second time, is calculated, with the second time different to the first time. A position of the GNSS receiver is calculated based at least in part on the accumulated pseudorange differences.

Abstract: A method and apparatus are provided for processing a plurality of GNSS measurements to infer state information. An example method includes obtaining a plurality of quality indicators associated with each GNSS measurement. A space of joint values of the plurality of quality indicators is divided into at least a first region and a second region. Neither the first region nor the second region is box-shaped. The method determines whether the plurality of quality indicators fall within the first region or the second region. If the plurality of quality indicators fall within the first region, the GNSS measurement in question is included in the processing to infer the state information. Also provided is a method of estimating residual error models for GNSS measurements, based on training data.

Abstract: A method and apparatus are disclosed for processing GNSS measurements. The GNSS measurements comprise carrier phase measurements. A state vector is defined, comprising state variables. A posterior probability density for the state vector is obtained, which is based on non-Gaussian residual error models for the GNSS measurements. A systematic search of the posterior probability density is performed, to identify a set of modes of the probability density.

Abstract: A method and apparatus are provided for processing GNSS measurements to infer state information. An example method includes obtaining one or more residual error models for the plurality of GNSS measurements. The one or more residual error models describe a probability distribution of errors in each of the GNSS measurements. The method further includes inferring the state information based on the one or more residual error models. The GNSS measurements include at least one carrier phase measurement. The residual error model for the at least one carrier phase measurement is cyclic, such that errors in carrier phase that are separated by an integer number of cycles are regarded as equivalent. The probability distribution for the at least one carrier phase measurement comprises a function having a continuous first derivative, for example, a continuous first derivative at a phase boundary between successive cycles.

Abstract: The present disclosure provides an authentication method for a satellite-based navigation system that in some implementations includes: obtaining, by an authentication server, a plurality of message authentication bundles from a plurality of reference receiver stations, each message authentication bundle comprising at least one hash for authenticating a corresponding SNS message received by a respective reference receiver station from at least one satellite of the SNS; inserting, by the authentication server at least a subset of the hashes of the obtained message authentication bundles into a probabilistic data structure (PDS), which forms at least a part of a validation filter for authenticating a corresponding subset of SNS messages; and distributing the validation filter to at least one receiver-side device.

Abstract: An apparatus includes an antenna assembly including an antenna configured to receive a signal and generate, at a plurality of feed points of the antenna, a plurality of corresponding polarized signals having respective polarization directions different from each other, using the received signal; and a switching circuit configured to periodically switch between the plurality of feed points to select a corresponding one of the polarized signals among the plurality of polarized signals at a point of time based on a switching signal.

Abstract: An apparatus includes an antenna assembly including an antenna configured to receive a signal and generate, at a plurality of feed points of the antenna, a plurality of corresponding polarized signals having respective polarization directions different from each other, using the received signal; and a switching circuit configured to periodically switch between the plurality of feed points to select a corresponding one of the polarized signals among the plurality of polarized signals at a point of time based on a switching signal.

Abstract: A method of compensating for the temperature related frequency drift of an oscillator. The method comprises using an external reference frequency signal to derive oscillator compensation data over a range of operating temperatures, storing the oscillator compensation data in a first table, and, for a given operating temperature, using the first table to obtain corresponding oscillator compensation data and applying that data to provide compensation for the temperature related frequency drift. The method further comprises defining, for the range of operating temperatures, a series of temperature slots each sub-divided into a series of temperature bins.

Abstract: A method of compensating for the temperature related frequency drift of an oscillator. The method comprises using an external reference frequency signal to derive oscillator compensation data over a range of operating temperatures, storing the oscillator compensation data in a first table, and, for a given operating temperature, using the first table to obtain corresponding oscillator compensation data and applying that data to provide compensation for the temperature related frequency drift. The method further comprises defining, for the range of operating temperatures, a series of temperature slots each sub-divided into a series of temperature bins.

Abstract: This invention provides methods for a GPS device to resolve timing errors as applicable to a AGPS navigation solution, and, in particular, to solutions involving GNSS positioning and timing with limited assistance such as indoors or in a heavily obscured location, where the time of transmit of satellite signals is not directly extractable from the navigation message data. In particular the invention concerns the reconstruction of time-of-transmit from the course acquisition code of weak signals or where assisted-GNSS are employed.

Abstract: A method is disclosed for providing syntonisation, synchronization, position or some combination to a wireless base station, micro-cell, pico-cell, femto-cell or access point, by providing holdover backup in a GPS clock module via at least one interface between the GPS clock module and an external time or frequency reference. Switching between synchronization modes is designed to occur on the control side of the oscillator portion of the module rather than at the output of two oscillators. A corresponding GPS clock module apparatus is disclosed for providing holdover backup via at least one interface between the GPS clock module and external time or frequency references.

Abstract: The invention provides a GPS device that resolves timing errors as applicable to an AGPS navigation solution. A single state algorithm provides rapid convergence, typical with standard Newton-Raphson performance. Problems due to ill-conditioning of the input matrix are identified by an augmented DOP calculation procedure, which may be used to identify unreliable results or to estimate the errors for those results.

Abstract: This invention provides methods for a GPS device to resolve timing errors as applicable to a AGPS navigation solution, and, in particular, to solutions involving GNSS positioning and timing with limited assistance such as indoors or in a heavily obscured location, where the time of transmit of satellite signals is not directly extractable from the navigation message data. In particular the invention concerns the reconstruction of time-of-transmit from the course acquisition code of weak signals or where assisted-GNSS are employed.

Abstract: The invention provides a GPS device that resolves timing errors as applicable to an AGPS navigation solution. A single state algorithm provides rapid convergence, typical with standard Newton-Raphson performance. Problems due to ill-conditioning of the input matrix are identified by an augmented DOP calculation procedure, which may be used to identify unreliable results or to estimate the errors for those results.

Abstract: A method, device and system for determining a receiver location using weak signal satellite transmissions. The invention involves a sequence of exchanges between an aiding source and a receiver that serve to provide aiding information to the receiver so that the receiver's location may be determined in the presence of weak satellite transmissions. With the aiding information, the novel receiver detects, acquires and tracks weak satellite signals and computes position solutions from calculated pseudo ranges despite the inability to extract time synchronization date f, 'n the weak satellite signals. The invention includes as features, methods and apparatus for the calibration of a local oscillator, the cancellation of cross correlations, a Doppler location scheme, an ensemble averaging scheme, the calculation of almanac aiding from a table of orbit coefficients, absolute time determination, and a modified search engine.