Spatial processing and timing estimation using a training sequence in a radio communications system
First Claim
1. A method comprising:
- receiving a burst having a known training sequence at a set of diversity antennas;
sampling the received burst at each antenna;
determining a coarse timing estimate for samples from at least one antenna;
calculating a spatial weighting vector using values computed in determining the coarse timing estimate;
applying the spatial weighting vector to the received burst samples for each antenna to form a single channel signal;
determining a fine timing estimate for the single channel signal;
determining a second spatial weighting vector using the fine timing estimate;
applying the second spatial weighting vector to the received burst samples for each antenna to form a second single channel signal; and
demodulating the second single channel signal.
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Abstract
A method and apparatus are provided that performs spatial processing, timing estimation and frequency offset using a training sequence of a received burst. According to one aspect of the present invention, the invention includes receiving a burst having a known training sequence at a set of diversity antennas, sampling the received burst at each antenna, determining a coarse timing estimate for samples from at least one antenna, and determining a spatial weighting vector using the coarse timing estimate. The embodiment further includes applying the spatial weighting vector to the received burst samples for each antenna to form a single channel signal, determining a fine timing estimate for the single channel signal, determining a second spatial weighting vector using the fine timing estimate, applying the second spatial weighting vector to the received burst samples for each antenna to form a second single channel signal, and demodulating the second single channel signal.
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Citations
25 Claims
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1. A method comprising:
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receiving a burst having a known training sequence at a set of diversity antennas;
sampling the received burst at each antenna;
determining a coarse timing estimate for samples from at least one antenna;
calculating a spatial weighting vector using values computed in determining the coarse timing estimate;
applying the spatial weighting vector to the received burst samples for each antenna to form a single channel signal;
determining a fine timing estimate for the single channel signal;
determining a second spatial weighting vector using the fine timing estimate;
applying the second spatial weighting vector to the received burst samples for each antenna to form a second single channel signal; and
demodulating the second single channel signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 21, 24)
calculating a cross correlation vector for a portion of the samples with respect to a selected part of the known training sequence, each cross correlation vector corresponding to a relative timing hypothesis and each cross correlation vector combining samples that occur at intervals within an analysis window;
calculating a least squares fit for each hypothesis using the calculated cross correlation vectors; and
selecting the combination of samples corresponding to the minimal least squares fit as the coarse timing of the received burst.
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6. The method of claim 5, wherein calculating a least squares fit comprises comparing a hypothetical received sequence to the known training sequence for each hypothesis.
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7. The method of claim 6, wherein the hypothetical received sequence is determined based on the cross correlation vector and a Cholesky factor.
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8. The method of claim 5, wherein calculating a cross correlation vector comprises calculating a cross correlation vector for a portion of evenly spaced ones of the samples.
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9. The method of claim 5, wherein determining a fine timing estimate further comprises determining the fine timing of the selected combination of samples by applying a timing estimation algorithm to an interpolated sequence of the selected combination of samples.
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21. The method of claim 1, wherein the burst is configured in accordance with at least one of a TDMA, a FDMA, a CDMA and a TDD radio communications system.
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24. The method of claim 5, wherein calculating a spatial weighting vector comprise using a Cholesky factor and the cross correlation vector corresponding to the selected combination of samples.
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10. A machine-readable medium having stored thereon data representing sequences of instructions which, when executed by a machine, cause the machine to perform operations comprising:
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receiving a burst having a known training sequence at a set of diversity antennas;
sampling the received burst at each antenna;
determining a coarse timing estimate for samples from at least one antenna;
calculating a spatial weighting vector using values computed in determining the coarse timing estimate;
applying the spatial weighting vector to the received burst samples for each antenna to form a single channel signal;
determining a fine timing estimate for the single channel signal;
determining a second spatial weighting vector using the fine timing estimate;
applying the second spatial weighting vector to the received burst samples for each antenna to form a second single channel signal; and
demodulating the second single channel signal. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 22, 25)
calculating a cross correlation vector for a portion of the samples with respect to a selected part of the training sequence, each cross correlation vector corresponding to a relative timing hypothesis and each cross correlation vector combining samples that occur at intervals within an analysis window;
calculating a least squares fit for each hypothesis using the calculated cross correlation vectors; and
selecting the combination of samples corresponding to the minimal least squares fit as the coarse timing of the received burst.
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15. The medium of claim 14, wherein the instructions for calculating a least squares fit further comprise instructions which, when executed by the machine, cause the machine to perform further operations comprising comparing a hypothetical received sequence to the known sequence for each hypothesis.
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16. The medium of claim 15, wherein the hypothetical received sequence is determined based on the cross correlation vector and a Cholesky factor.
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17. The medium of claim 14, wherein the instructions for calculating a cross correlation vector further comprise instructions which, when executed by the machine, cause the machine to perform further operations comprising calculating a cross correlation vector for a portion of evenly spaced ones of the samples.
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18. The method of claim 14, wherein the instructions for determining a fine timing estimate further comprise instructions which, when executed by the machine, cause the machine to perform further operations comprising determining the fine timing of the selected combination of samples by applying a timing estimation algorithm to an interpolated sequence of the selected combination of samples.
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22. The medium of claim 10, wherein the burst is configured in accordance with at least one of a TDMA, a FDMA, a CDMA and a TDD radio communications system.
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25. The medium of claim 14, wherein the instructions for calculating a spatial weighting vector further comprise instructions which, when executed by the machine, cause the machine to perform further operations comprising using a Cholesky factor and the cross correlation vector corresponding to the selected combination of samples.
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19. An apparatus comprising:
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a set of diversity antennas to receive a burst having a known training sequence;
means for sampling the received burst at each antenna;
means for determining a coarse timing estimate for samples from at least one antenna;
means for calculating a spatial weighting vector using values computed in determining the coarse timing estimate;
means for applying the spatial weighting vector to the received burst samples for each antenna to form a single channel signal;
means for determining a fine timing estimate for the single channel signal;
means for determining a second spatial weighting vector using the fine timing estimate;
means for applying the second spatial weighting vector to the received burst samples for each antenna to form a second single channel signal; and
means for demodulating the second single channel signal. - View Dependent Claims (20, 23)
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Specification