Quick detection of signaling in a wireless communication system

• US 8,027,373 B2
• Filed: 09/15/2005
• Issued: 09/27/2011
• Est. Priority Date: 09/15/2005
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Chawla, Vivek, Sheshadri, Thejaswi Bharadwaj Madapushi, Subrahmanya, Parvathanathan
• Primary Examiner(s): Nguyen; Duc
• Assistant Examiner(s): Jain; Ankur
• Application Number:
  US11/228,045
• Publication Number:
  US 20070060095A1
• Time in Patent Office: 2,203 Days
• Field of Search: 455/522
• US Class Current: 375/149
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 2201/70709 with discontinuous detection
• CPC Class Codes: H04L 2027/003 at baseband only
• CPC Class Codes: H04L 2027/0034 using hypothesis testing
• CPC Class Codes: H04L 2027/0065 Frequency error detectors H04L2027/0067 takes precedence
• CPC Class Codes: H04L 27/2278 using correlation techniques, e.g. for spread spectrum signals
• CPC Class Codes: H04W 52/0229 where the received signal is a wanted signal
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Quick frequency tracking (QFT), quick time tracking (QTT), and non-causal pilot filtering (NCP) are used to detect sporadically transmitted signaling, e.g., paging indicators. For QFT, multiple hypothesized frequency errors are applied to an input signal to obtain multiple rotated signals. The energies of the rotated signals are computed. The hypothesized frequency error with the largest energy is provided as a frequency error estimate. For QTT, coherent accumulation is performed on the input signal for a first set of time offsets, e.g., early, on-time, and late. Interpolation, energy computation, and non-coherent accumulation are then performed to obtain a timing error estimate with higher time resolution. For NCP, pilot symbols are filtered with a non-causal filter to obtain pilot estimates for one antenna for non-STTD and for two antennas for STTD. The frequency and timing error estimates and the pilot estimates are used to detect the signaling.

Claims

1. An apparatus, comprising:

a processor operative to perform quick frequency tracking to obtain at least one frequency error estimate for at least one finger processor and to perform quick time tracking to obtain at least one timing error estimate for the at least one finger processor; and

a demodulator operative to perform detection for signaling with the at least one frequency error estimate and the at least one timing error estimate for the at least one finger processor;

wherein the quick frequency tracking comprises an open-loop frequency estimation technique; and

wherein the demodulator is operative to filter pilot symbols with a non-causal filter to obtain pilot estimates and to perform detection for the signaling based on the pilot estimates.

2. The apparatus of claim 1, wherein the processor is operative, for each finger processor, to perform coherent accumulation to obtain energies for a plurality of hypothesized frequency errors and to determine a frequency error estimate for the finger processor based on the energies for the plurality of hypothesized frequency errors.

3. The apparatus of claim 1, wherein the processor is operative, for each finger processor, to perform coherent accumulation, interpolation, and non-coherent accumulation to obtain energies for a plurality of time offsets and to determine a timing error estimate for the finger processor based on the energies for the plurality of time offsets.

4. The apparatus of claim 1, wherein the processor is operative to perform quick frequency tracking and quick time tracking in parallel.

5. The apparatus of claim 1, wherein the controller is operative to determine an amount of time to perform quick frequency tracking and quick time tracking in a next awake interval based on expected channel conditions and to determine a sleep duration based on the amount of time to perform quick frequency tracking and quick time tracking in the next awake interval.

6. The apparatus of claim 1, wherein the processor is operative to perform detection for a paging indicator sent at a predetermined time interval.

7. The apparatus of claim 1, further comprising:

a rotator coupled to the processor;

a sampling unit coupled to the processor; and

a descrambler coupled to the rotator for descrambling rotated signals from the rotator,

wherein the processor is operative, for each finger processor, to provide the at least one frequency error estimate to the rotator, the rotator for performing phase rotation on output samples from the sampling unit responsive to the at least one frequency error estimate and providing the rotated signals to the descrambler.

8. The apparatus of claim 1, wherein the quick time tracking comprises an open-loop timing estimation technique.

9. A method, comprising:

performing quick frequency tracking to obtain at least one frequency error estimate for at least one finger processor;

performing quick time tracking to obtain at least one timing error estimate for the at least one finger processor;

performing detection of signaling with the at least one frequency error estimate and the at least one timing error estimate for the at least one finger processor;

wherein the quick time tracking comprises an open-loop timing estimation technique; and

filtering pilot symbols with a non-causal filter to obtain pilot estimates, and wherein the detection of the signaling is performed based on the pilot estimates.

10. The method of claim 9, wherein the performing quick frequency tracking comprises, for each finger processor,

performing coherent accumulation to obtain energies for a plurality of hypothesized frequency errors, and

determining a frequency error estimate for the finger processor based on the energies for the plurality of hypothesized frequency errors.

11. The method of claim 10, further comprising performing phase rotation on signals from a sampling unit responsive to the at least one frequency error estimate.

12. The method of claim 9, wherein the performing quick time tracking comprises, for each finger processor,

performing coherent accumulation, interpolation, and non-coherent accumulation to obtain energies for a plurality of time offsets, and

determining a timing error estimate for the finger processor based on the energies for the plurality of time offsets.

13. The method of claim 12, wherein the performing of the coherent accumulation comprises performing the coherent accumulation on an input signal for a first plurality of time offsets;

wherein the performing of the interpolation comprises performing interpolation from the first plurality of time offsets to a second plurality of time offsets; and

wherein the performing of the non-coherent accumulation comprises performing the non-coherent accumulation after the performing of the interpolation to obtain the timing error estimate.

14. The method of claim 9, further comprising:

determining an amount of time to perform quick frequency tracking and quick time tracking in a next awake interval based on expected channel conditions; and

determining a sleep duration based on the amount of time to perform quick frequency tracking and quick time tracking in the next awake interval.

15. The method of claim 9, wherein the quick frequency tracking comprises an open-loop frequency estimation technique.

16. An apparatus, comprising:

means for performing quick frequency tracking to obtain at least one frequency error estimate for at least one finger processor;

means for performing quick time tracking to obtain at least one timing error estimate for the at least one finger processor;

means for performing detection of signaling with the at least one frequency error estimate and the at least one timing error estimate for the at least one finger processor;

wherein the quick frequency tracking comprises an open-loop frequency estimation technique; and

means for filtering pilot symbols with a non-causal filter to obtain pilot estimates, and wherein the detection of the signaling is performed based on the pilot estimates.

17. The apparatus of claim 16, wherein the means for performing quick frequency tracking comprises, for each finger processor,

means for performing coherent accumulation to obtain energies for a plurality of hypothesized frequency errors, and

means for determining a frequency error estimate for the finger processor based on the energies for the plurality of hypothesized frequency errors.

18. The apparatus of claim 17, further comprising means for performing phase rotation on signals from a sampling unit responsive to the at least one frequency error estimate.

19. The apparatus of claim 16, wherein the means for performing quick time tracking comprises, for each finger processor,

means for performing coherent accumulation, interpolation, and non-coherent accumulation to obtain energies for a plurality of time offsets, and

means for determining a timing error estimate for the finger processor based on the energies for the plurality of time offsets.

20. The apparatus of claim 19, wherein the means for performing the coherent accumulation comprises means for performing the coherent accumulation on an input signal for a first plurality of time offsets;

wherein the means for performing the interpolation comprises means for performing interpolation from the first plurality of time offsets to a second plurality of time offsets; and

wherein the means for performing of the non-coherent accumulation comprises means for performing the non-coherent accumulation after the performing of the interpolation to obtain the timing error estimate.

21. The apparatus of claim 16, wherein the quick time tracking comprises an open-loop timing estimation technique.

22. An apparatus, comprising:

a processor operative to perform quick frequency tracking to obtain at least one frequency error estimate for at least one finger processor and to perform quick time tracking to obtain at least one timing error estimate for the at least one finger processor; and

a demodulator operative to perform detection for signaling with the at least one frequency error estimate and the at least one timing error estimate for the at least one finger processor,

wherein the quick frequency tracking comprises an open-loop frequency estimation technique

a rotator coupled to the processor;

a sampling unit coupled to the processor; and

a descrambler coupled to the rotator for descrambling rotated signals from the rotator,

wherein the processor is operative, for each finger processor, to provide the at least one frequency error estimate to the rotator, the rotator for performing phase rotation on output samples from the sampling unit responsive to the at least one frequency error estimate and providing the rotated signals to the descrambler

wherein the processor is operative, for each finger processor, to identify a largest energy among energies of the rotated signals and to provide a hypothesized frequency error corresponding to the largest energy as the frequency error estimate.

23. The apparatus of claim 22, wherein the processor is operative, for each finger processor, to perform coherent accumulation to obtain energies for a plurality of hypothesized frequency errors and for a plurality of time offsets, and to determine a frequency error estimate and a timing error estimate for the finger processor based on the energies for the plurality of hypothesized frequency errors and the plurality of time offsets, respectively.

24. An apparatus comprising:

a processor operative to perform quick frequency tracking to obtain at least one frequency error estimate for at least one finger processor and to perform quick time tracking to obtain at least one timing error estimate for the at least one finger processor;

a demodulator operative to perform detection for signaling with the at least one frequency error estimate and the at least one timing error estimate for the at least one finger processor;

wherein the quick frequency tracking comprises an open-loop frequency estimation technique;

a rotator coupled to the processor;

a sampling unit coupled to the processor; and

a receiver unit coupled to the at least one finger processor;

wherein the processor is operative, for each finger processor, to provide the at least one timing error estimate to the sampling unit, the sampling unit for receiving input samples from the receiver unit and providing output samples at a different sampling rate from that of the input samples to the rotator.

25. The apparatus of claim 24, wherein the sampling rate of the output samples is two times chip rate.

26. The apparatus of claim 24, wherein the processor is operative, for each finger processor, to perform coherent accumulation on an input signal for a first plurality of time offsets, to perform interpolation from the first plurality of time offsets to a second plurality of time offsets, and to perform non-coherent accumulation after the interpolation to obtain the timing error estimate.

27. The apparatus of claim 26, wherein the processor is operative, for each finger processor, to perform linear interpolation on outputs of the coherent accumulation for the first plurality of time offsets to obtain intermediate values for the second plurality of time offsets and to perform non-coherent accumulation based on the intermediate values.

28. The apparatus of claim 27, wherein the processor is operative, for each finger processor, to compute energies of the intermediate values for the second plurality of time offsets and to perform non-coherent accumulation based on the energies of the intermediate values for the second plurality of time offsets.

29. The apparatus of claim 28, wherein the processor is operative, for each finger processor, to identify a largest energy among non-coherently accumulated energies for the second plurality of time offsets and to provide a time offset corresponding to the largest energy as the timing error estimate.

30. The apparatus of claim 26, wherein the processor is operative, for each finger processor, to perform parabolic interpolation on outputs of the non-coherent accumulation for the first plurality of time offsets.

31. A method, comprising:

performing quick frequency tracking to obtain at least one frequency error estimate for at least one finger processor;

performing quick time tracking to obtain at least one timing error estimate for the at least one finger processor;

performing detection of signaling with the at least one frequency error estimate and the at least one timing error estimate for the at least one finger processor;

wherein the quick time tracking comprises an open-loop timing estimation technique;

wherein the performing quick frequency tracking comprises, for each finger processor;

performing coherent accumulation to obtain energies for a plurality of hypothesized frequency errors;

determining a frequency error estimate for the finger processor based on the energies for the plurality of hypothesized frequency errors; and

performing phase rotation on signals from a sampling unit responsive to the at least one frequency error estimate;

wherein the determining of the frequency error estimate for the finger processor comprises identifying a largest energy among energies of rotated signals and identifying a hypothesized frequency error corresponding to the largest energy as the frequency error estimate.

32. The method of claim 31, wherein the performing quick frequency tracking comprises, for each finger processor:

performing coherent accumulation to obtain energies for a plurality of hypothesized frequency errors; and

determining a frequency error estimate for the finger processor based on the energies for the plurality of hypothesized frequency errors;

wherein the performing quick time tracking comprises, for each finger processor;

performing coherent accumulation, interpolation, and non-coherent accumulation to obtain energies for a plurality of time offsets; and

determining a timing error estimate for the finger processor based on the energies for the plurality of time offsets.

33. A method, comprising:

performing quick frequency tracking to obtain at least one frequency error estimate for at least one finger processor;

performing quick time tracking to obtain at least one timing error estimate for the at least one finger processor;

performing detection of signaling with the at least one frequency error estimate and the at least one timing error estimate for the at least one finger processor;

wherein the quick time tracking comprises an open-loop timing estimation technique;

wherein the performing quick time tracking comprises, for each finger processor;

performing coherent accumulation, interpolation, and non-coherent accumulation to obtain energies for a plurality of time offsets;

determining a timing error estimate for the finger processor based on the energies for the plurality of time offsets;

wherein the performing of the coherent accumulation comprises performing the coherent accumulation on an input signal for a first plurality of time offsets;

wherein the performing of the interpolation comprises performing interpolation from the first plurality of time offsets to a second plurality of time offsets;

wherein the performing of the non-coherent accumulation comprises performing the non-coherent accumulation after the performing of the interpolation to obtain the timing error estimate; and

performing linear interpolation on outputs of the coherent accumulation for the first plurality of time offsets to obtain intermediate values for the second plurality of time offsets;

wherein the performing of the non-coherent accumulation is based on the intermediate values.

34. The method of claim 33, further comprising computing energies of the intermediate values for the second plurality of time offsets,

wherein the performing of the non-coherent accumulation is based on the energies of the intermediate values for the second plurality of time offsets.

35. The method of claim 34, further comprising identifying a largest energy among non-coherently accumulated energies for the second plurality of time offsets,

wherein the timing error estimate for the finger processor comprises a time offset corresponding to the largest energy.

36. An apparatus, comprising:

means for performing quick frequency tracking to obtain at least one frequency error estimate for at least one finger processor;

means for performing quick time tracking to obtain at least one timing error estimate for the at least one finger processor;

means for performing detection of signaling with the at least one frequency error estimate and the at least one timing error estimate for the at least one finger processor;

wherein the quick frequency tracking comprises an open-loop frequency estimation technique;

wherein the means for performing quick frequency tracking comprises, for each finger processor;

means for performing coherent accumulation to obtain energies for a plurality of hypothesized frequency errors; and

means for determining a frequency error estimate for the finger processor based on the energies for the plurality of hypothesized frequency errors; and

means for performing phase rotation on signals from a sampling unit responsive to the at least one frequency error estimate;

wherein the means for determining the frequency error estimate for the finger processor comprises means for identifying a largest energy among energies of the rotated signals and means for identifying a hypothesized frequency error corresponding to the largest energy as the frequency error estimate.

37. The apparatus of claim 36, wherein the means for performing quick frequency tracking comprises, for each finger processor:

means for performing coherent accumulation to obtain energies for a plurality of hypothesized frequency errors; and

means for determining a frequency error estimate for the finger processor based on the energies for the plurality of hypothesized frequency errors;

wherein the means for performing quick time tracking comprises, for each finger processor;

means for performing coherent accumulation, interpolation, and non-coherent accumulation to obtain energies for a plurality of time offsets; and

means for determining a timing error estimate for the finger processor based on the energies for the plurality of time offsets.

38. An apparatus, comprising:

means for performing quick frequency tracking to obtain at least one frequency error estimate for at least one finger processor;

means for performing quick time tracking to obtain at least one timing error estimate for the at least one finger processor;

means for performing detection of signaling with the at least one frequency error estimate and the at least one timing error estimate for the at least one finger processor;

wherein the quick frequency tracking comprises an open-loop frequency estimation technique;

wherein the means for performing quick time tracking comprises, for each finger processor;

means for performing coherent accumulation, interpolation, and non-coherent accumulation to obtain energies for a plurality of time offsets; and

means for determining a timing error estimate for the finger processor based on the energies for the plurality of time offsets;

wherein the means for performing the coherent accumulation comprises means for performing the coherent accumulation on an input signal for a first plurality of time offsets;

wherein the means for performing the interpolation comprises means for performing interpolation from the first plurality of time offsets to a second plurality of time offsets;

wherein the means for performing of the non-coherent accumulation comprises means for performing the non-coherent accumulation after the performing of the interpolation to obtain the timing error estimate; and

means for performing linear interpolation on outputs of the coherent accumulation for the first plurality of time offsets to obtain intermediate values for the second plurality of time offsets;

wherein the means for performing of the non-coherent accumulation is configured to base the performance of the non-coherent accumulation on the intermediate values.

39. The apparatus of claim 38, further comprising means for computing energies of the intermediate values for the second plurality of time offsets,

wherein the means for performing the non-coherent accumulation is configured to base the performance of the non-coherent accumulation on the energies of the intermediate values for the second plurality of time offsets.

40. The apparatus of claim 39, further comprising means for identifying a largest energy among non-coherently accumulated energies for the second plurality of time offsets,

wherein the timing error estimate for the finger processor comprises a time offset corresponding to the largest energy.

41. A computer program product, comprising:

a non-transitory computer-readable medium, comprising;

codes for causing a computer to perform quick frequency tracking to obtain at least one frequency error estimate for at least one finger processor;

codes for causing a computer to perform quick time tracking to obtain at least one timing error estimate for the at least one finger processor;

codes for causing a computer to perform detection of signaling with the at least one frequency error estimate and the at least one timing error estimate for the at least one finger processor;

wherein the quick time tracking comprises an open-loop timing estimation technique; and

filtering pilot symbols with a non-causal filter to obtain pilot estimates, and wherein the detection of the signaling is performed based on the pilot estimates.

42. The computer program product of claim 41, wherein the codes for performing quick frequency tracking comprises, for each finger processor,

codes for causing a computer to perform coherent accumulation to obtain energies for a plurality of hypothesized frequency errors, and

codes for causing a computer to determine a frequency error estimate for the finger processor based on the energies for the plurality of hypothesized frequency errors.

43. The computer program product of claim 41, wherein the codes for performing quick time tracking comprises, for each finger processor,

codes for causing a computer to perform coherent accumulation, interpolation, and non-coherent accumulation to obtain energies for a plurality of time offsets, and

codes for causing a computer to determine a timing error estimate for the finger processor based on the energies for the plurality of time offsets.

44. The computer program product of claim 41, further comprising:

codes for causing a computer to determine an amount of time to perform quick frequency tracking and quick time tracking in a next awake interval based on expected channel conditions; and

codes for causing a computer to determine a sleep duration based on the amount of time to perform quick frequency tracking and quick time tracking in the next awake interval.

45. A computer program product, comprising:

a non-transitory computer-readable medium, comprising;

codes for causing a computer to perform quick frequency tracking to obtain at least one frequency error estimate for at least one finger processor;

codes for causing a computer to perform quick time tracking to obtain at least one timing error estimate for the at least one finger processor;

codes for causing a computer to perform detection of signaling with the at least one frequency error estimate and the at least one timing error estimate for the at least one finger processor;

wherein the quick time tracking comprises an open-loop timing estimation technique;

wherein the codes for performing quick frequency tracking comprises, for each finger processor;

codes for causing a computer to perform coherent accumulation to obtain energies for a plurality of hypothesized frequency errors;

codes for causing a computer to determine a frequency error estimate for the finger processor based on the energies for the plurality of hypothesized frequency errors; and

codes for causing a computer to perform phase rotation on signals from a sampling unit responsive to the at least one frequency error estimate;

wherein the determining of the frequency error estimate for the finger processor comprises identifiing a largest energy among energies of the rotated signals and identifiing a hypothesized frequency error corresponding to the largest energy as the frequency error estimate.

46. A computer program product, comprising:

a non-transitory computer-readable medium, comprising;

codes for causing a computer to perform quick frequency tracking to obtain at least one frequency error estimate for at least one finger processor;

codes for causing a computer to perform quick time tracking to obtain at least one timing error estimate for the at least one finger processor;

codes for causing a computer to perform detection of signaling with the at least one frequency error estimate and the at least one timing error estimate for the at least one finger processor;

wherein the quick time tracking comprises an open-loop timing estimation technique;

wherein the codes for performing quick time tracking comprises, for each finger processor;

codes for causing a computer to perform coherent accumulation, interpolation, and non-coherent accumulation to obtain energies for a plurality of time offsets;

codes for causing a computer to determine a timing error estimate for the finger processor based on the energies for the plurality of time offsets;

wherein the performing of the coherent accumulation comprises performing the coherent accumulation on an input signal for a first plurality of time offsets;

wherein the performing of the interpolation comprises performing interpolation from the first plurality of time offsets to a second plurality of time offsets; and

wherein the performing of the non-coherent accumulation comprises performing the noncoherent accumulation after the performing of the interpolation to obtain the timing error estimate; and

codes for causing a computer to perform linear interpolation on outputs of the coherent accumulation for the first plurality of time offsets to obtain intermediate values for the second plurality of time offsets;

wherein the performing of the non-coherent accumulation is based on the intermediate values.

47. The computer program product of claim 46, further comprising codes for causing a computer to compute energies of the intermediate values for the second plurality of time offsets,

wherein the performing of the non-coherent accumulation is based on the energies of the intermediate values for the second plurality of time offsets.

48. The computer program product of claim 47, further comprising codes for causing a computer to identify a largest energy among non-coherently accumulated energies for the second plurality of time offsets,

wherein the timing error estimate for the finger processor comprises a time offset corresponding to the largest energy.