Transmit diversity pilot processing
First Claim
1. An apparatus, comprising:
- a sum estimator for producing an estimate of the sum of a primary channel and a diversity channel in response to a received symbol;
a difference estimator for producing an estimate of the difference of the primary channel and the diversity channel in response to a received symbol;
a controller for updating the sum estimator when the received symbol comprises a sum of the primary and diversity channels and for updating the difference estimator when the received symbol comprises a difference of the primary and diversity channels; and
a parameter estimator for producing a primary channel estimate and a diversity channel estimate from the estimate of the sum and the estimate of the difference of the primary and diversity channels.
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Abstract
Techniques for improved diversity pilot estimation in rapidly changing channel environments are disclosed. In one aspect, a difference estimate is updated when a current received symbol comprises a difference between the primary and diversity channels, and a sum estimate is updated when a current received symbol comprises a sum of the primary and diversity channels. The primary channel and the diversity channel are estimated in response to the sum estimate and the difference estimate. In another aspect, the sum estimate and difference estimate are produced by filtering the received symbols. In yet another aspect, received symbols are demodulated in response to the primary and diversity channel estimates. These aspects have the benefit of incorporating the most recently received symbol, resulting in more accurate channel estimates and hence improved demodulation performance, increased system capacity, lower required transmit power, and other benefits.
25 Citations
25 Claims
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1. An apparatus, comprising:
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a sum estimator for producing an estimate of the sum of a primary channel and a diversity channel in response to a received symbol;
a difference estimator for producing an estimate of the difference of the primary channel and the diversity channel in response to a received symbol;
a controller for updating the sum estimator when the received symbol comprises a sum of the primary and diversity channels and for updating the difference estimator when the received symbol comprises a difference of the primary and diversity channels; and
a parameter estimator for producing a primary channel estimate and a diversity channel estimate from the estimate of the sum and the estimate of the difference of the primary and diversity channels. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A wireless communication device, comprising:
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a sum estimator for producing an estimate of the sum of a primary channel and a diversity channel in response to a received symbol;
a difference estimator for producing an estimate of the difference of the primary channel and the diversity channel in response to a received symbol;
a controller for updating the sum estimator when the received symbol comprises a sum of the primary and diversity channels and for updating the difference estimator when the received symbol comprises a difference of the primary and diversity channels; and
a parameter estimator for producing a primary channel estimate and a diversity channel estimate from the estimate of the sum and the estimate of the difference of the primary and diversity channels.
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10. A communication system, comprising:
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a sum estimator for producing an estimate of the sum of a primary channel and a diversity channel in response to a received symbol;
a difference estimator for producing an estimate of the difference of the primary channel and the diversity channel in response to a received symbol;
a controller for updating the sum estimator when the received symbol comprises a sum of the primary and diversity channels and for updating the difference estimator when the received symbol comprises a difference of the primary and diversity channels; and
a parameter estimator for producing a primary channel estimate and a diversity channel estimate from the estimate of the sum and the estimate of the difference of the primary and diversity channels.
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11. An apparatus, operable with a base station configured for transmit diversity, the base station transmitting a first pilot sequence on a first antenna and a second pilot sequence on a second antenna, the second sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence, the symbols consisting of a pre-determined number of chips, comprising:
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a despreader for despreading received samples with the first pilot sequence;
an accumulator for accumulating the pre-determined number of despread samples to produce a received symbol;
a first filter for filtering received symbols when the current value of the orthogonalizing sequence is positive;
a second filter for filtering received symbols when the current value of the orthogonalizing sequence is negative; and
a parameter estimator for generating a primary channel estimate and a diversity channel estimate from the output of the first and second filters.
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12. A method of channel estimation for use in a transmit diversity communication system, comprising:
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producing a difference estimate with a most recently received symbol when the symbol comprises a difference between the primary and diversity channels;
producing a sum estimate with a most recently received symbol when the symbol comprises a sum of the primary and diversity channels;
producing a primary channel estimate from the difference estimate and the sum estimate; and
producing a diversity channel estimate from the difference estimate and the sum estimate. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A method of channel estimation, suitable for use in a transmit diversity communication system, including a base station transmitting a first pilot sequence on a first antenna and a second pilot sequence on a second antenna, the second sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence, the symbols consisting of a pre-determined number of chips, the method comprising:
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filtering a current received symbol when the current value of the orthogonalizing sequence is positive to produce a sum estimate;
filtering a current received symbol when the current value of the orthogonalizing sequence is negative to produce a difference estimate; and
generating a primary channel estimate and a diversity channel estimate from the sum estimate and the difference estimate.
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20. An apparatus, comprising:
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means for producing a difference estimate with a most recently received symbol when the symbol comprises a difference between the primary and diversity channels;
means for producing a sum estimate with a most recently received symbol when the symbol comprises a sum of the primary and diversity channels;
means for producing a primary channel estimate from the difference estimate and the sum estimate; and
means for producing a diversity channel estimate from the difference estimate and the sum estimate.
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21. A wireless communication device, comprising:
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means for producing a difference estimate with a most recently received symbol when the symbol comprises a difference between the primary and diversity channels;
means for producing a sum estimate with a most recently received symbol when the symbol comprises a sum of the primary and diversity channels;
means for producing a primary channel estimate from the difference estimate and the sum estimate; and
means for producing a diversity channel estimate from the difference estimate and the sum estimate.
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22. A communication system, comprising:
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means for producing a difference estimate with a most recently received symbol when the symbol comprises a difference between the primary and diversity channels;
means for producing a sum estimate with a most recently received symbol when the symbol comprises a sum of the primary and diversity channels;
means for producing a primary channel estimate from the difference estimate and the sum estimate; and
means for producing a diversity channel estimate from the difference estimate and the sum estimate.
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23. An apparatus, operable with a base station configured for transmit diversity, the base station transmitting a first pilot sequence on a first antenna and a second pilot sequence on a second antenna, the second sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence, the symbols consisting of a pre-determined number of chips, comprising:
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a means for filtering a current received symbol when the current value of the orthogonalizing sequence is positive to produce a sum estimate;
a means for filtering a current received symbol when the current value of the orthogonalizing sequence is negative to produce a difference estimate; and
a means for generating a primary channel estimate and a diversity channel estimate from the sum estimate and the difference estimate.
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24. Processor readable media operable to perform the following steps:
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producing a difference estimate with a most recently received symbol when the symbol comprises a difference between the primary and diversity channels;
producing a sum estimate with a most recently received symbol when the symbol comprises a sum of the primary and diversity channels;
producing a primary channel estimate from the difference estimate and the sum estimate; and
producing a diversity channel estimate from the difference estimate and the sum estimate.
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25. Processor readable media, operable with a base station transmitting a first pilot sequence on a first antenna and a second pilot sequence on a second antenna, the second sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence, the symbols consisting of a pre-determined number of chips, the media operable to perform the following steps:
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filtering a current received symbol when the current value of the orthogonalizing sequence is positive to produce a sum estimate;
filtering a current received symbol when the current value of the orthogonalizing sequence is negative to produce a difference estimate; and
generating a primary channel estimate and a diversity channel estimate from the sum estimate and the difference estimate.
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Specification