Frequency offset compensation improvement for a long term evolution (LTE) searcher

1. A method for processing communication signals to determine frequency offset compensation in a wireless communication device, the method comprising:

correlating a received signal with each of a plurality of sub-replica sequences to obtain a vector of matched filter output values associated with a time offset identified by at least one correlation time index value;

generating, for each of the at least one correlation time index value, a correlation score using a combined energy associated with a combination of the matched filter output values corresponding to all the sub-replica sequences;

determining, for each of the at least one correlation time index value, a first phase difference computed as an average phase difference between the matched filter output values associated with adjacent sub-replica sequences;

generating, for each of a subset of the at least one correlation time index value, a second phase difference computed using a linear combination of neighbor first phase differences and a primary first phase difference corresponding to the correlation score within a subset of highest correlation scores; and

computing, for each of the subset of the at least one correlation index value, an estimate of frequency error using the second phase difference, wherein said frequency error estimate is utilized by the wireless communication device to compensate for a frequency offset in subsequent received signals.

2. The method of claim 1 , wherein said generating the second phase difference further comprises:

linearly combining the at least one neighbor first phase difference with the primary first phase difference to determine the second phase difference.

3. The method of claim 1 , wherein said generating the second phase difference further comprises:

computing the second phase difference using a weighted average of the at least one neighbor first phase difference and the primary first phase difference, wherein a second correlation time index of said at least one correlation time index value corresponds to a neighbor correlation score and said neighbor correlation score is generated using a combined energy associated with a combination of the matched filter output values indexed by the second correlation time index value over all of the sub-replica sequences.

4. The method of claim 3 , wherein said generating the second phase difference further comprises:

determining coefficient values for linearly weighting the at least one neighbor first phase difference and the primary first phase difference associated with the primary correlation score by using a ratio of the primary correlation score and the neighbor correlation score corresponding to each one of the at least one neighbor first phase difference;

wherein said determining further comprises:

providing one of: (a) substantially equal weighting for the at least one neighbor first phase difference in response to determining that the ratio of the primary and neighbor correlation scores are substantially equal to one; (b) substantially zero weighting for the at least one neighbor first phase difference in response to determining that the ratio of the primary and neighbor correlation scores are within a first pre-determined range, where the primary correlation score is substantially greater than the neighbor correlation score; and (c) a linearly determined weighting for the at least one neighbor first phase difference in response to determining that the ratio of the primary and neighbor correlation scores are within a second predetermined range that is greater than the first pre-determined range.

5. The method of claim 3 , wherein said generating the second phase difference further comprises:

determining an ideal correlation time index as a fractional time index between the primary correlation time index and a neighbor correlation time index; and

determining, using the ideal correlation time index, coefficient values for combining the at least one neighbor first phase difference with the primary first phase difference associated with the primary correlation score to determine the second phase difference.

6. The method of claim 1 , wherein said generating the second phase difference further comprises:

sorting a vector of correlation scores corresponding to the at least one correlation time index value;

selecting a collection of the highest correlation scores from among the plurality of correlation scores within the sorted vector by using a peak vector size limit that provides a pre-determined number of the highest correlation scores and provides reduced computational complexity; and

determining the second phase difference using (a) the primary first phase difference associated with a highest correlation score from among the selected collection of the highest correlation scores and (b) the at least one corresponding neighbor phase difference.

7. The method of claim 1 , wherein:

said frequency error is associated with a first local oscillator of the wireless communication device and a second local oscillator of a base-station; and

the frequency error is estimated without requiring a precise establishment of the sample timing.

8. The method of claim 1 , wherein said providing the estimate of frequency error further comprises:

computing the frequency error estimate associated with a particular correlation time index by: performing an angle operation on the second phase difference; and converting, to a frequency value, an angular value obtained from performing the angle operation on the second phase difference.

9. The method of claim 1 , further comprising:

generating a replica signal of a reference signal being transmitted from a base-station;

creating the sub-replica sequences of the generated replica signal using time-offset partitions of the generated replica signal; and

triggering said correlating in response to receipt of the first signal.

10. A baseband modem integrated circuit (BMIC) being utilized within a wireless communication device, the BMIC comprising:

at least one matched filter correlator that correlates a received signal with each of a plurality of sub-replica sequences to obtain a vector of matched filter output values associated with a time offset identified by at least one correlation time index value;

an energy computation component that computes energy associated with the match filter output values;

a correlation score generator that determines, for the at least one correlation time index value, a correlation score using a combined energy associated with the matched filter output values corresponding to all the sub-replica sequences;

a first phase difference generator that determines, for the at least one correlation time index value, a first phase difference computed as an average phase difference between the matched filter output values for adjacent sub-replica sequences; and

a second, refined phase difference generator that determines, for a subset of the at least one correlation time index value, a second phase difference computed using a linear combination of neighbor first phase differences and a primary first phase difference corresponding to the correlation score within a subset of highest correlation scores; and

a frequency error estimator, triggered by the second phase difference generator, that computes, for the subset of the at least one correlation index value, an estimate of frequency error using the second phase difference, wherein said frequency error estimate is utilized by the wireless communication device to compensate for a frequency offset in subsequent received signals.

11. The BMIC of claim 10 , wherein said second phase difference generator further comprising logic that:

linearly combines the at least one neighbor first phase difference with the primary first phase difference to determine the second phase difference; and

performs the linear combining by providing one of:

(a) substantially equal weighting for the at least one neighbor first phase difference in response to determining that a ratio of the primary and neighbor correlation scores are substantially equal to one; (b) substantially zero weighting for the at least one neighbor first phase difference in response to determining that the ratio of the primary and neighbor correlation scores are within a first pre-determined range, where the primary correlation score is substantially greater than the neighbor correlation score; and (c) linearly determined weighting for the at least one neighbor first phase difference in response to determining that the ratio of the primary and neighbor correlation scores are within a second predetermined range that is greater than the first pre-determined range.

12. The BMIC of claim 10 , wherein said second phase difference generator further comprising logic that:

computes the second phase difference using a weighted average of the at least one neighbor first phase difference and the primary first phase difference, wherein said at least one second correlation time index value corresponds to a neighbor correlation score and said neighbor correlation score is generated using a combined energy associated with a combination of the matched filter output values indexed by the second correlation time index value over all the sub-replica sequences.

13. The BMIC of claim 12 , wherein said second phase difference generator further comprising logic that:

determines coefficient values for linearly weighting the at least one neighbor first phase difference and the primary first phase difference associated with the primary correlation score by using a ratio of the primary correlation score and the neighbor correlation score corresponding to each one of the at least one neighbor first phase difference.

14. The BMIC of claim 12 , wherein said second phase difference generator further comprising logic that:

determines an ideal correlation time index as a fractional time index between the primary correlation time index and a neighbor correlation time index; and

determines, using the ideal correlation time index, coefficient values for combining the at least one neighbor first phase difference with the primary first phase difference associated with the primary correlation score to determine the second phase difference.

15. The BMIC of claim 10 , wherein said second phase difference generator further comprising logic that:

triggers a correlation score peak selector to:

sort a vector of correlation scores corresponding to the at least one correlation time index value;

select a collection of the highest correlation scores from among the plurality of correlation scores within the sorted vector by using a peak vector size limit that provides a pre-determined number of the highest correlation scores and provides reduced computational complexity; and

determine the second phase difference using (a) the primary first phase difference associated with a highest correlation score from among the selected collection of the highest correlation scores and (b) the at least one corresponding neighbor phase difference; and

determines the second phase difference using the neighbor phase differences associated with the selected collection of the highest primary correlation scores that correspond to the subset of the at least one correlation time index value.

16. The BMIC of claim 10 , wherein:

said frequency error is associated with a first local oscillator of the wireless communication device and a second local oscillator of a base-station; and

the frequency error is estimated without requiring a precise establishment of the sample timing.

17. The BMIC of claim 10 , wherein said second phase difference generator further comprising logic that:

triggers the frequency error estimator to compute the frequency error estimate associated with a particular correlation index value, and

wherein said frequency error estimator further comprising logic that:

performs an angle operation on the second phase difference; and

converts, to a frequency value, an angular value obtained from performing the angle operation on the second phase difference.

18. The BMIC of claim 10 , further comprising logic that:

generates a replica signal of a reference signal being transmitted from a base-station;

creates the sub-replica sequences of the generated replica signal using time-offset partitions of the generated replica signal; and

triggers the BMIC to perform the correlation of the received signal with each of the plurality of sub-replica sequences to obtain the vector of matched filter output values in response to receipt of the received signal.

19. A wireless communication device comprising a baseband modem integrated circuit (BMIC) that includes:

at least one matched filter correlator that correlates a received signal with each of a plurality of sub-replica sequences to obtain a vector of matched filter output values associated with a time offset identified by at least one correlation time index value;

an energy computation component that computes energy associated with the match filter output values;

a correlation score generator that determines, for the at least one correlation time index value, a correlation score using a combined energy associated with a combination of the matched filter output values corresponding to all the sub-replica sequences;

a first phase difference generator that determines, for the at least one correlation time index value, a first phase difference computed as an average phase difference between the matched filter output values for adjacent sub-replica sequences; and

a second, refined phase difference generator that determines, for each of a subset of the at least one correlation time index value, a second phase difference computed using a linear combination of neighbor first phase differences and a primary first phase difference corresponding to the correlation score within a subset of highest correlation scores; and

a frequency error estimator, triggered by the second phase difference generator, that computes for the subset of the at least one correlation index value, an estimate of frequency error using the second phase difference, wherein said frequency error estimate is utilized by the wireless communication device to compensate for a frequency offset in subsequent received signals.

20. The wireless communication device of claim 19 , wherein the second phase difference generator further comprising logic that:

determines an ideal correlation time index as a fractional time index between the first correlation time index and a neighbor correlation time index;

determines coefficient values for linearly weighting the at least one neighbor first phase difference and the primary first phase difference associated with the primary correlation score by using at least one of the ideal correlation time index and a ratio of the primary correlation score and a neighbor correlation score corresponding to each one of the at least one neighbor first phase difference, wherein said neighbor correlation score is generated using a combined energy associated with a combination of the matched filter output values indexed by the second correlation time index value over all the sub-replica sequences;

computes a second phase difference using a weighted average of the at least one neighbor first phase difference and the primary first phase difference associated with the primary correlation score; and

triggers the frequency error estimator to compute the frequency error estimate associated with a particular correlation index value, wherein said frequency error estimator further comprising logic that:

performs an angle operation on the second phase difference; and

converts, to a frequency value, an angular value obtained from performing the angle operation on the second phase difference.