Method and system for determining carrier frequency offsets for positioning signals
First Claim
1. A method for directly extracting carrier frequency offsets (CFOs) from positioning signals received at a ranging receiver, the positioning signals comprising a plurality of samples, the method comprising:
- for each of a previously determined number of decimated samples, accumulating a specified number of samples into the decimated sample;
determining whether to apply rate correction to the decimated samples;
applying a particular number of rate corrections to each decimated sample to generate a set of results when rate correction is to be applied;
storing each set of results;
determining whether a minimum number of significant carriers exists in the sets of stored results; and
determining the CFOs based on the significant carriers when the minimum number of significant carriers exists in the sets of stored results.
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Accused Products
Abstract
A method for directly extracting carrier frequency offsets (CFOs) from positioning signals received at a ranging receiver is provided. The positioning signals comprise a plurality of samples. The method includes, for each of a previously determined number of decimated samples, accumulating a specified number of samples into the decimated sample. A determination is made regarding whether to apply rate correction to the decimated samples. A particular number of rate corrections are applied to each decimated sample to generate a set of results when rate correction is to be applied. Each set of results is stored. A determination is made regarding whether a minimum number of significant carriers exists in the sets of stored results. The CFOs are determined based on the significant carriers when the minimum number of significant carriers exists in the sets of stored results.
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Citations
46 Claims
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1. A method for directly extracting carrier frequency offsets (CFOs) from positioning signals received at a ranging receiver, the positioning signals comprising a plurality of samples, the method comprising:
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for each of a previously determined number of decimated samples, accumulating a specified number of samples into the decimated sample;
determining whether to apply rate correction to the decimated samples;
applying a particular number of rate corrections to each decimated sample to generate a set of results when rate correction is to be applied;
storing each set of results;
determining whether a minimum number of significant carriers exists in the sets of stored results; and
determining the CFOs based on the significant carriers when the minimum number of significant carriers exists in the sets of stored results. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A system for directly extracting carrier frequency offsets (CFOs) from positioning signals received at a ranging receiver, the positioning signals comprising a plurality of samples, the system comprising:
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a computer-processable medium; and
logic stored on the computer-processable medium, the logic operable to, for each of a previously determined number of decimated samples, accumulate a specified number of samples into the decimated sample, to determine whether to apply rate correction to the decimated samples, to apply a particular number of rate corrections to each decimated sample to generate a set of results when rate correction is to be applied, to store each set of results, to determine whether a minimum number of significant carriers exists in the sets of stored results, and to determine the CFOs based on the significant carriers when the minimum number of significant carriers exists in the sets of stored results. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30)
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31. A system for directly extracting carrier frequency offsets (CFOs) from positioning signals received at a ranging receiver, the positioning signals comprising a plurality of samples, the system comprising:
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means for accumulating, for each of a previously determined number of decimated samples, a specified number of samples into the decimated sample;
means for determining whether to apply rate correction to the decimated samples;
means for applying a particular number of rate corrections to each decimated sample to generate a set of results when rate correction is to be applied;
means for storing each set of results;
means for determining whether a minimum number of significant carriers exists in the sets of stored results; and
means for determining the CFOs based on the significant carriers when the minimum number of significant carriers exists in the sets of stored results. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45)
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46. A method for directly extracting carrier frequency offsets (CFOs) from positioning signals received at a ranging receiver, the positioning signals comprising a plurality of samples, the method comprising:
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for each of a previously determined number of decimated samples, accumulating a specified number of samples into the decimated sample, the specified number of samples selected to yield a decimated sample with at least a 20 kHz bandwidth, the previously determined number of decimated samples corresponding to a sampled duration of approximately one second;
determining whether to apply rate correction to the decimated samples;
applying a particular number of rate corrections to each decimated sample to generate a set of results when rate correction is to be applied, the particular number of rate corrections selected based on a desired error range between rate corrections;
storing each set of results;
determining whether a minimum number of significant carriers exists in the sets of stored results by Fourier-transforming each set of stored results into a frequency domain and searching a spectrum for each Fourier-transformed set of stored results for significant carriers, the minimum number of significant carriers comprising four significant carriers, significant carriers comprising carriers at least 6 dB above a noise-background threshold;
determining the CFOs based on the significant carriers when the minimum number of significant carriers exists in the sets of stored results;
when the minimum number of significant carriers does not exist in the sets of stored results, accumulating the specified number of samples into additional decimated samples up to a maximum number of decimated samples until the minimum number of significant carriers exists in the sets of stored results, the maximum number of decimated samples corresponding to a sampled duration between approximately 5 and 100 seconds; and
setting a flag to indicate that the positioning signals received at the ranging receiver are too weak for CFO extraction when the maximum number of decimated samples is formed.
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Specification