Method and apparatus of cross-correlation with application to channel estimation and detection

1. A method for determining a cross-correlation between a reference sequence and a received sequence in a wireless communication system, the reference sequence comprising a set of sub-sequences that have been sign-adjusted and concatentated, the sign adjustments determined by a first sign sequence, the method comprising:

shifting the received sequence to provide a plurality of time shifted sequences;

cross-correlating the plurality of time shifted sequences with sub-sequences of the set of sub-sequences to form a set of partial cross-correlations;

sign-adjusting the partial cross-correlations using the first sign sequence; and

combining the sign-adjusted partial cross-correlations to produce the cross-correlation between the reference sequence and the received sequence, where the cross-correlation is used by the wireless communication system to facilitate wireless communication,

where the first sign sequence is a sign sequence of a plurality of sign sequences, the method further comprising:

for each sign sequence of the plurality of sign sequences:

sign-adjusting the partial cross-correlations using the sign sequence;

combining the sign-adjusted partial cross-correlations to form a cross-correlation corresponding to the sign sequence; and

producing a metric of the cross-correlation corresponding to the sign sequence; and

detecting the first sign sequence as the sign-sequence of the plurality of sign sequences for which the metric is maximized.

2. The method of claim 1 , where the plurality of sign sequences corresponds to a plurality of channel signatures, further comprising:

identifying, from the plurality of channel signatures, a channel signature of the received sequence as the channel signature corresponding to the sign sequence for which the metric is maximized.

3. The method of claim 1 , further comprising:

determining a channel impulse response as the cross-correlation for which the metric is maximized.

4. The method of claim 1 , where the metric comprises a norm of the cross-correlation over a range of lags.

5. The method of claim 1 , where the received sequence is received via a communication channel, further comprising:

estimating an impulse response of the communication channel from the cross-correlation between the reference sequence and the received sequence.

6. A method for determining a cross-correlation between a reference sequence and a received sequence in a wireless communication system, the reference sequence comprising a set of sub-sequences that have been sign-adjusted and concatentated, the sign adjustments determined by a first sign sequence, the method comprising:

shifting the received sequence to provide a plurality of time shifted sequences;

cross-correlating the plurality of time shifted sequences with sub-sequences of the set of sub-sequences to form a set of partial cross-correlations;

sign-adjusting the partial cross-correlations using the first sign sequence; and

combining the sign-adjusted partial cross-correlations to produce the cross-correlation between the reference sequence and the received sequence, where the cross-correlation is used by the wireless communication system to facilitate wireless communication,

where the received sequence is over-sampled compared to the chip rate of the received sequence, the method further comprising:

forming a plurality of parallel chip-rate phases from the received sequence;

cross-correlating the plurality of parallel chip-rate phases with the reference sequence, in accordance with claim 1 , to provide a plurality of correlations;

determining the phase of a strongest correlation of the plurality of correlations in accordance with a metric; and

processing the plurality of correlations dependent upon the phase of the strongest correlation.

7. The method of claim 6 , where processing the plurality of correlations comprises:

selecting a correlation of the plurality of correlations having the strongest metric.

8. The method of claim 6 , where processing the plurality of correlations comprises:

outputting the metric of the correlation of the plurality of correlations having the strongest metric.

9. The method of claim 6 , where processing the plurality of correlations comprises:

converting the parallel correlations to a serial correlation at the oversampled rate; and

sub-sampling the serial correlation dependent upon the phase of the strongest correlation of the plurality of correlations.

10. A system operable to determine a cross-correlation between a reference sequence and a received sequence in a wireless communication system, the reference sequence comprising a set of sub-sequences that have been sign-adjusted and concatentated, the sign adjustments determined by a first sign sequence of a plurality of sign sequences, the system comprising:

a plurality of shift modules operable to shift the received sequence by an amount dependent upon the length of the sub-sequences to provide a plurality of shifted received sequences;

a plurality of correlators operable to form a plurality of partial cross-correlations by correlating a shifted received sequence with a sub-sequence of the set of sub-sequences; and

at least one combiner operable to adjust signs of the plurality of partial cross-correlations in accordance with the first sign sequence and sum the sign adjusted partial correlations to provide the cross-correlation between the reference sequence and the received sequence, where the cross-correlation is used by the wireless communication system

where the plurality of shift modules comprises a series cascade of shift modules each operable to shift the received sequence by the length of the sub-sequences.

11. The system of claim 10 , where the reference sequence comprises an alternating concatenation of sign-adjusted Golay complementary pair sub-sequences.

12. An electronic device comprising:

a receiver operable to recover a received sequence from a received communication signal;

a correlator operable to determine a cross-correlation between a reference sequence and the received sequence, the reference sequence comprising a set of sub-sequences that have been sign-adjusted and concatentated, the sign adjustments determined by a first sign sequence of a plurality of sign sequences, the correlator comprising:

a plurality of shift modules operable to shift the received sequence by an amount dependent upon a length of the sub-sequences to provide a plurality of shifted received sequences;

a plurality of partial correlators operable to form a plurality of partial cross-correlations by correlating a shifted received sequences with a sub-sequence;

at least one combiner operable to adjust signs of the plurality of partial cross-correlations in accordance with the first sign sequence and sum the sign adjusted partial correlations to provide the cross-correlation between the reference sequence and the received sequence; and

a processor operable to process the received sequence dependent upon the cross-correlation between the reference sequence and the received sequence for use during wireless communication,

where the first sign sequence is a sign sequence of a plurality of sign sequences, where the at least one combiner is further operable, for each sign sequence of the plurality of sign sequences, to:

sign-adjust the partial cross-correlations using the sign sequence; and

combine the sign-adjusted partial cross-correlations to form a cross-correlation corresponding to the sign sequence; and

where the processor is further operable to:

produce a metric of the cross-correlation corresponding to the sign sequence for each sign sequence of the plurality of sign sequences; and

detect the first sign sequence as the sign-sequence of the plurality of sign sequences for which the metric is maximized.

13. A system operable to determine a cross-correlation between a set of M reference sequences and a received sequence in a wireless communication system, each reference sequence of the set of reference sequences comprising a concatenation of sign-adjusted sub-sequences, the sign adjustments determined by a sign sequence of a set of M sign sequences, the system comprising:

a serial-to-parallel converter responsive to the received sequence, over-sampled at R times the chip rate of the received sequence, and operable to provide R phase-adjusted chip-rate sequences;

R chip-rate correlators, each operable to produce M chip-rate correlations between a phase-adjusted chip-rate sequence and the M reference sequences; and

M phase selectors, each responsive to R chip-rate correlations for a reference sequence of the M reference sequences and operable to select a chip-rate correlation for which a metric of the chip-rate correlation is maximized, where the chip-rate correlation selected facilitates wireless communication.

14. The system of claim 13 , where a chip-rate correlator of the R chip-rate correlators comprises:

a plurality of shift modules operable to shift the chip-rate sequence by an amount dependent upon the length of the sub-sequences to provide a plurality of shifted chip-rate sequences;

a plurality of correlators operable to form a plurality of partial cross-correlations by correlating a shifted chip-rate sequences with a sub-sequence; and

M combiners each operable to adjust the signs of the plurality of partial cross-correlations in accordance with a sign sequence of the M sign sequences and sum the sign adjusted partial correlations to provide the cross-correlation between the corresponding reference sequence and the chip-rate sequence.

15. The system of claim 13 , where M is greater than one and where the M phase selectors are each operable to output a maximum value of the metric, the system further comprising:

a comparator responsive to the M maximum metric values, and operable to identify the reference sequence and the associated phase-adjusted correlation corresponding to the largest maximum metric value.

16. The system of claim 13 , where a phase selector of the M phase selectors is operable to output the phase for which the metric is maximized, the system further comprising:

a multiplexer, responsive to the phase, operable to select the chip-rate correlation of the R chip-rate correlations dependent upon the phase, and operable to output a phase-adjusted correlation.

17. The system of claim 16 , where the phase-adjusted correlation comprises a channel impulse response.

18. An electronic device comprising:

a receiver operable to recover a received sequence from a received communication signal;

a correlator operable to determine a cross-correlation between a set of M reference sequences and the received sequence, each reference sequence of the set of reference sequences comprising a concatenation of sign-adjusted sub-sequences, the sign adjustments determined by a sign sequence of a set of M sign sequences, the correlator comprising:

a serial-to-parallel converter responsive to the received sequence, over-sampled at R times the chip rate of the received sequence, and operable to provide R phase-adjusted chip-rate sequences;

R chip-rate correlators, each operable to produce M chip-rate correlations between a phase-adjusted chip-rate sequence and the M reference sequences; and

M phase selectors, each responsive to R chip-rate correlations for a reference sequence of the M reference sequences and operable to select the chip-rate correlation for which a metric of the correlation is maximized; and

a processor operable to process the received sequence dependent upon the cross-correlation between the reference sequence and the received sequence for use during wireless communication.

19. A non-transitory computer-readable medium having processor-executable instructions that, when executed by a processor, cause the processor to:

shift a received sequence to provide a plurality of time shifted sequences;

cross-correlate the plurality of time shifted sequences with the sub-sequences to form a set of partial cross-correlations;

sign-adjust the partial cross-correlations using a first sign sequence; and

combine the sign-adjusted partial cross-correlations to produce the cross-correlation between the reference sequence and the received sequence, where the cross-correlation is used by the processor to facilitate wireless communication,

the non-transitory computer-readable medium having further processor-executable instructions that, when executed by a processor, cause the processor to:

for each sign sequence of a plurality of sign sequences:

sign-adjust the partial cross-correlations using the sign sequence;

combine the sign-adjusted partial cross-correlations to form a cross-correlation corresponding to the sign sequence; and

produce a metric of the cross-correlation corresponding to the sign sequence; and

detect the first sign sequence as the sign-sequence of the plurality of sign sequences for which the metric is maximized.

20. The non-transitory computer-readable medium of claim 19 having further processor-executable instructions that, when executed by a processor, cause the processor to:

identify a channel signature of the received sequence as the channel signature corresponding to the detected first sign sequence.

21. The non-transitory computer-readable medium of claim 19 having further processor-executable instructions that, when executed by a processor, cause the processor to:

identify a channel impulse response from the cross-correlation corresponding to the detected first sign sequence.