Time tracking loop for diversity pilots
First Claim
1. A time tracking apparatus, operable with a base station configured for transmit diversity, transmitting a first pilot sequence on a first antenna and a second pilot sequence on a second antenna, the second pilot sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence, the symbols consisting of a first pre-determined number of chips, comprising:
- a first timing offset for receiving input samples and for generating an early sequence of samples corresponding to a first pre-determined offset before a timing reference;
a second timing offset for receiving input samples and for generating a late sequence of samples corresponding to a second pre-determined offset after a timing reference;
a first despreader for despreading the early sequence of samples with the first pilot sequence;
a second despreader for despreading the late sequence of samples with the first pilot sequence;
a first accumulator for accumulating despread samples from the first despreader for a second pre-determined number of chips to produce a first accumulation;
a second accumulator for accumulating despread samples from the second despreader for the second pre-determined number of chips to produce a second accumulation;
a first magnitude squarer for generating a first squared magnitude from the first accumulation;
a second magnitude squarer for generating a second squared magnitude from the second accumulation;
a subtractor for generating the difference between the first and second squared magnitudes;
a tracking loop for receiving the difference from the subtractor and for generating the timing reference in response to the difference; and
a pilot decover for estimating the first and second pilots from the input samples in accordance with the timing reference.
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Accused Products
Abstract
Techniques for time tracking diversity pilots are disclosed. In one aspect, an early and a late energy calculation is made on each incoming symbol using a first pilot sequence for despreading. The difference between the two energies is used to drive a tracking loop, which generates a time reference for producing a first pilot estimate and a second pilot estimate, the two estimates used for demodulating data. In another aspect, the early and late energies are made including a plurality of incoming symbols, the number of which corresponds to the number of symbols in a run of positive or negative values in an orthogonalizing sequence. The orthogonalizing sequence is used to generate a second pilot sequence from a first pilot sequence, the resulting second pilot sequence being orthogonal to the first. These aspects have the benefit of simplifying the hardware or processing steps required for transmit diversity time tracking, resulting in cost savings, power savings, simplicity of design, and the like.
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Citations
15 Claims
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1. A time tracking apparatus, operable with a base station configured for transmit diversity, transmitting a first pilot sequence on a first antenna and a second pilot sequence on a second antenna, the second pilot sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence, the symbols consisting of a first pre-determined number of chips, comprising:
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a first timing offset for receiving input samples and for generating an early sequence of samples corresponding to a first pre-determined offset before a timing reference; a second timing offset for receiving input samples and for generating a late sequence of samples corresponding to a second pre-determined offset after a timing reference; a first despreader for despreading the early sequence of samples with the first pilot sequence; a second despreader for despreading the late sequence of samples with the first pilot sequence; a first accumulator for accumulating despread samples from the first despreader for a second pre-determined number of chips to produce a first accumulation; a second accumulator for accumulating despread samples from the second despreader for the second pre-determined number of chips to produce a second accumulation; a first magnitude squarer for generating a first squared magnitude from the first accumulation; a second magnitude squarer for generating a second squared magnitude from the second accumulation; a subtractor for generating the difference between the first and second squared magnitudes; a tracking loop for receiving the difference from the subtractor and for generating the timing reference in response to the difference; and a pilot decover for estimating the first and second pilots from the input samples in accordance with the timing reference. - View Dependent Claims (5, 9, 10)
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2. A time tracking apparatus, operable with a base station configured for transmit diversity, transmitting a first pilot sequence on a first antenna and a second pilot sequence on a second antenna, the second pilot sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence, the symbols consisting of a first pre-determined number of chips, comprising:
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a first timing offset for receiving input samples and for generating an early sequence of samples corresponding to a first pre-determined offset before a timing reference; a second timing offset for receiving input samples and for generating a late sequence of samples corresponding to a second pre-determined offset after a timing reference; a first despreader fox despreading the early sequence of samples with the first pilot sequence; a second despreader for despreading the late sequence of samples with the first pilot sequence; a first accumulator for accumulating despread samples from the first despreader for a second pre-determined number of chips to produce a first accumulation; a second accumulator for accumulating despread samples from the second despreader for the second pre-determined number of chips to produce a second accumulation; a first magnitude squarer for generating a first squared magnitude from the first accumulation; a second magnitude squarer for generating a second squared magnitude from the second accumulation; a subtractor for generating the difference between the first and second squared magnitudes; a tracking loop for generating the timing reference in response to the difference; and a pilot decover for estimating the first and second pilots from the input samples in accordance with the timing reference, wherein the second pre-determined number of chips equals the first pre-determined number of chips. - View Dependent Claims (3)
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4. A time tracking apparatus, operable with a base station configured for transmit diversity, transmitting a first pilot sequence on a first antenna and a second pilot sequence on a second antenna, the second pilot sequence generated by multiplying each symbol of the first pilot by a value from an orthogonalizing sequence, the symbols consisting of a first pre-determined number of chips, comprising:
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a first timing offset for receiving input samples and for generating an early sequence of samples corresponding to a first pre-determined offset before a timing reference; a second timing offset for receiving input samples and for generating a late sequence of samples corresponding to a second pre-determined offset after a timing reference; a first despreader for despreading the early sequence of samples with the first pilot sequence; a second despreader for despreading the late sequence of samples with the first pilot sequence; a first accumulator for accumulating despread samples from the first despreader for a second pre-determined number of chips to produce a first accumulation; a second accumulator for accumulating despread samples from the second despreader for the second pre-determined number of chips to produce a second accumulation; a first magnitude squarer for generating a first squared magnitude from the first accumulation; a second magnitude squarer for generating a second squared magnitude from the second accumulation; a subtracter for generating the difference between the first and second squared magnitudes; a tracking loop for generating the timing reference in response to the difference; and a pilot decover for estimating the first and second pilots from the input samples in accordance with the timing reference, wherein the first and second timing offsets are one timing offset.
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6. A time tracking apparatus, operable with a base station configured for transmit diversity, transmitting a first pilot sequence on a first antenna and a second pilot sequence on a second antenna, the second pilot sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence, the symbols consisting of a first pre-determined number of chips, comprising:
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a first timing offset for receiving input samples and for generating an early sequence of samples corresponding to a first pre-determined offset before a timing reference; a second timing offset for receiving input samples and for generating a late sequence of samples corresponding to a second pre-determined offset after a timing reference; a first despreader for despreading the early sequence of samples with the first pilot sequence; a second despreader for despreading the late sequence of samples with the first pilot sequence; a first accumulator for accumulating despread samples from the first despreader for a second pre-determined number of chips to produce a first accumulation; a second accumulator for accumulating despread samples from the second despreader for the second pre-determined number of chips to produce a second accumulation; a first magnitude squarer for generating a first a squared magnitude from the first accumulation; a second magnitude squarer for generating a second squared magnitude from the second accumulation; a subtractor for generating the difference between the first and second squared magnitudes; a tracking loop for generating the timing reference in response to the difference; and a pilot decover for estimating the first and second pilots from the input samples in accordance with the timing reference, wherein; the orthogonalizing sequence comprises alternating runs of positive values with runs of negative values, the runs being a pre-determined number of values; the second pre-determined number of chips equals the first pre-determined number of chips multiplied by the pre-determined number of values in a run; and the first and second accumulators align the accumulation with the runs. - View Dependent Claims (7, 8)
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11. A method of time tracking a plurality of pilot sequences, a first pilot sequence transmitted from a first antenna, each of the remaining plurality of pilot sequences transmitted on a corresponding plurality of antennas, each remaining pilot sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence of a plurality of orthogonalizing sequences, the symbols consisting of a first pre-determined number of chips, comprising:
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calculating a difference between the energy in a correlation of the first pilot sequence with an early received sequence of input samples and the energy in a correlation of the first pilot sequence with a late received sequence of input samples, the correlations for a pre-determined length, the early and late sequences referenced to a timing reference; updating a tracking loop with the difference to produce the timing reference; and estimating the plurality of pilot sequences in accordance with the timing reference wherein; the orthogonalizing sequence comprises alternating runs of positive values with runs of negative values, the runs being a pre-determined number of values; the pre-determined length equals the pre-determined number of chips multiplied by the pre-determined number of values in a run; and the correlation is aligned with the runs.
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12. A method of time tracking a plurality of pilot sequences, a first pilot sequence transmitted from a first antenna, each of the remaining plurality of pilot sequences transmitted on a corresponding plurality of antennas, each remaining pilot sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence of a plurality of orthogonalizing sequences, the symbols consisting of a first pre-determined number of chips, comprising:
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calculating a difference between the energy in a correlation of the first pilot sequence with an early received sequence of input samples and the energy in a correlation of the first pilot sequence with a late received sequence of input samples, the correlations for a pre-determined length, the early and late sequences referenced to a timing reference; updating a tracking loop with the difference to produce the timing reference; and estimating the plurality of pilot sequences in accordance with the timing reference wherein; the orthogonalizing sequence comprises alternating runs of positive values with runs of negative values, the runs being a pre-determined number of values; the pre-determined length equals the pre-determined number of chips multiplied by the pre-determined number of values in a run; and the correlation is aligned with the runs.
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13. A method of time tracking a plurality of pilot sequences, a first pilot sequence transmitted from a first antenna, each of the remaining plurality of pilot sequences transmitted on a corresponding plurality of antennas, each remaining pilot sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence of a plurality of orthogonalizing sequences, the symbols consisting of a first pre-determined number of chips, comprising:
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calculating a difference between the energy in a correlation of the first pilot sequence with an early received sequence of input samples and the energy in a correlation of the first pilot sequence with a late received sequence of input samples, the correlations for a pre-determined length, the early and late sequences referenced to a timing reference; updating a tracking loop with the difference to produce the timing reference; and estimating the plurality of pilot sequences in accordance with the timing reference wherein; the orthogonalizing sequences comprise alternating runs of positive values with runs of negative values, the runs being a pre-determined number of values; the pre-determined length equals the pre-determined number of chips multiplied by the pre-determined number of values in a run; and the correlation is aligned with the runs.
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14. A mobile station, operable with a base station configured for transmit diversity, transmitting a first pilot sequence on a first antenna and a second pilot sequence on a second antenna, the second pilot sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence, the symbols consisting of a first pre-determined number of chips, comprising:
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a first timing offset for receiving input samples and for generating an early sequence of samples corresponding to a first pre-determined offset before a timing reference; a second timing offset for receiving input samples and for generating a late sequence of samples corresponding to a second pre-determined offset after a timing reference; a first despreader for despreading the early sequence of samples with the first pilot sequence; a second despreader for despreading the late sequence of samples with the first pilot sequence; a first accumulator for accumulating despread samples from the first despreader for a second pre-determined number of chips to produce a first accumulation; a second accumulator for accumulating despread samples from the second despreader for the second pre-determined number of chips to produce a second accumulation; a first magnitude squarer for generating a first squared magnitude from the first accumulation; a second magnitude squarer for generating a second squared magnitude from the second accumulation; a subtractor for generating the difference between the first and second squared magnitudes; a tracking loop for receiving the difference from the subtraction and for generating the timing reference in response to the difference; and a pilot decover for estimating the first and second pilots from the input samples in accordance with the timing reference.
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15. An apparatus, operable with a remote station configured for transmit diversity, transmitting a first pilot sequence on a first antenna and a second pilot sequence on a second antenna, the second pilot sequence generated by multiplying each symbol of the first pilot sequence by a value from an orthogonalizing sequence, the symbols consisting of a first pre-determined number of chips, comprising:
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a timing offset with a timing reference input and a sample output; a first despreader with a first despreader input, a second despreader input, and an output; a second despreader with a first despreader input, a second despreader input, and an output; a first accumulator with an accumulator input and an output, the accumulator input coupled to the first despreader output; a second accumulator with an accumulator input and an output, the accumulator input coupled to the second despreader output; a first magnitude squarer with an input and an output, the first magnitude squarer input coupled to the first accumulator output; a second magnitude squarer with an input and an output, the second magnitude input coupled to the second accumulator output; a subtractor wit a first input second input, and an output, the first subtractor input coupled to the first magnitude squarer output, the second subtractor input coupled to the second magnitude squarer output; a tracking loop with an input and an output, the tracking loop input coupled to the subtractor output, the tracking loop output coupled to the timing offset timing reference input; and a pilot decover with a first pilot input, a second pilot input, and a sample input, the pilot decover first pilot input coupled to the first pilot, the pilot decover second pilot input coupled to the second pilot, the sample input coupled to the timing offset sample output.
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Specification