Satellite-based positioning system improvement
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.
1. In an SPS system for identifying the location of a receiver in the presence of satellite signal attenuation having a plurality of orbital satellites sending synchronized encoded signals on a carrier frequency wherein said encoded signals have repeated epochs containing synchronization data:
a receiver for detecting, acquiring, tracking a set of the encoded signals and simultaneously determining the code phases of said set with respect to said epochs; wherein said encoded signals are comprised of a signal power spectrum and noise; and
an aiding source to transmit information to the receiver,
wherein said receiver is comprised of a processor controlling a program to extract a signal power spectrum from the noise by averaging across a moving average, wherein said averaging includes executing a FFT across said power spectrum in which squared magnitudes of the resulting FFT bins are filtered and wherein multiple FFT calculations are performed.
2. An SPS system for identifying the location of a receiver in the presence of satellite signal attenuation comprising:
a plurality of orbital satellites sending synchronized encoded signals on a carrier frequency wherein said encoded signals have repeated epochs containing synchronization data;
a receiver for detecting, acquiring, tracking a set of the encoded signals and simultaneously determining the code phases of said set with respect to said epochs; wherein said encoded signals are comprised of a signal power spectrum and noise; and
an aiding source to transmit information to the receiver, and algorithm running in a processor that extracts said signal power spectrum from said noise by averaging the squared magnitude of an autoconvolution array of a FFT for each channel, through use of a filter.
3. An SPS system for identifying the location of a receiver in the presence of satellite signal attenuation comprising:
a plurality of orbital satellites sending synchronized encoded signals on a carrier frequency wherein said encoded signals have repeated epochs containing synchronization data;
a receiver for detecting, acquiring, tracking a set of the encoded signals and simultaneously determining the code phases of said set with respect to said epochs; wherein said encoded signals are comprised of a signal power spectrum and noise; and
an aiding source to transmit information to the receiver, wherein said receiver is comprised of a processor controlling a program to extract a signal power spectrum from the noise by averaging across a moving average wherein said averaging includes executing a FFT, wherein the number of FFT steps is comparable to the number of elements in said moving average.