Abstract: Methods and systems for demodulating GNSS navigation data bits in conditions that can cause a Doppler error, such as a GNSS receiver operating under a poor clock condition, in one aspect, include: receiving a modulated Global Navigation Satellite System (GNSS) carrier signal, wherein the GNSS carrier signal includes navigation bits; compensating for a Doppler error of the GNSS carrier signal using Doppler error compensation frequencies, wherein the compensating comprises determining in-phase (I) correlation results and quadrature (Q) correlation results at the Doppler error compensation frequencies; calculating dot products using the I correlation results and the Q correlation results from the compensating; determining a dot product from the calculated dot products having a maximum absolute value; and demodulating the GNSS carrier signal using the determined dot product having the maximum absolute value to extract the navigation bits from the GNSS carrier signal.

Abstract: Methods, systems, and apparatus for detecting poor Doppler measurements results in GNSS navigation, in one aspect, a method including: calculating a first Doppler shift value, wherein the first Doppler shift value is based on movement of a Global Navigation Satellite System (GNSS) receiver and calculated according to a Doppler measurement result; calculating a second Doppler shift value, wherein the second Doppler shift value is based on movement of the GNSS receiver and calculated according to a projection of velocity of the GNSS receiver on a line of sight (LOS) vector; comparing the first Doppler shift value with the second Doppler shift value to check an accuracy of the Doppler measurement result; and determining at least a direction of movement of the GNSS receiver in accordance with the checked accuracy of the Doppler measurement result.

Abstract: Aspects of the disclosure provide a method for multi-path interference detection. The method includes receiving, by a positioning device, a satellite signal transmitted from a satellite. The satellite signal carries a ranging code. Further, the method includes locking an internal code generated by the positioning device to the ranging code, determining characteristics of correlations between the satellite signal and the internal code with different time shifts, and detecting satellite signal deterioration due to multi-path interference based on the characteristics of the correlations between the satellite signal and the internal code with different time shifts.

Abstract: A receiver including a plurality of correlators to receive a satellite signal having a line of sight (LOS) component and a multipath (MP) component and generate correlator results corresponding to the received satellite signal. The receiver includes a peak search module to identify frequency peaks in the received satellite signal based on the correlator results, a peak selection module to identify the LOS component of the received satellite signal based on the identified frequency peaks and at least one of a code phase error module to generate a code phase error corresponding to the identified LOS component and a carrier frequency error module to generate a carrier frequency error corresponding to the identified LOS component. The plurality of correlators are further to generate the correlator results based on at least one of the code phase error and the carrier frequency error.

Abstract: System and methods are provided for clock calibration. A satellite navigation system includes: a timing component configured to determine a counting period for clock calibration; a counter network configured to determine a first number of local clock periods associated with a local clock of the satellite navigation system during the counting period and determine a second number of external clock periods associated with an external clock during the counting period; and a processor configured to perform calibration for the local clock based at least in part on the first number of the local clock periods and the second number of the external clock periods.

Abstract: Aspects of the disclosure provide an apparatus that includes a navigation signal receiver. The navigation signal receiver includes a receiving circuit configured to receive a satellite navigation signal from a satellite and a processing circuit configured to calculate a distance between the apparatus and the satellite based on the satellite navigation signal, and determine whether the apparatus is in a detection area based on the distance, a minimum distance from the detection area to the satellite and a maximum distance from the detection area to the satellite.

Abstract: System and methods are provided for clock calibration. A satellite navigation system includes: a timing component configured to determine a counting period for clock calibration; a counter network configured to determine a first number of local clock periods associated with a local clock of the satellite navigation system during the counting period and determine a second number of external clock periods associated with an external clock during the counting period; and a processor configured to perform calibration for the local clock based at least in part on the first number of the local clock periods and the second number of the external clock periods.