Quick detection of signaling in a wireless communication system

• US 8,170,084 B2
• Filed: 08/24/2011
• Issued: 05/01/2012
• Est. Priority Date: 09/15/2005
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Subrahmanya, Parvathanathan, Sheshadri, Thejaswi Bharadwaj Madapushi, Chawla, Vivek
• Primary Examiner(s): Nguyen, Duc
• Assistant Examiner(s): Jain, Ankur
• Application Number:
  US13/216,779
• Publication Number:
  US 20110306315A1
• Time in Patent Office: 251 Days
• Field of Search: 375/149
• 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 controller operative to wake up from sleep to receive signaling during discontinuous reception (DRX) operation;

a processor operative to apply a plurality of hypothesized frequency errors to an input signal to obtain a plurality of rotated signals, to determine energies of the plurality of rotated signals, and to determine a frequency error estimate based on the energies of the plurality of rotated signals;

a demodulator operative to use the frequency error estimate for detection of the signaling;

wherein the controller is operative to distribute the plurality of hypothesized frequency errors non-uniformly over a range of possible frequency errors and to use smaller frequency error spacing for at least one subrange of frequency errors with higher likelihood of containing an actual frequency error.

2. The apparatus of claim 1, wherein the processor is operative to accumulate each rotated signal over a predetermined period to obtain an accumulated value for the rotated signal and to compute energy of the accumulated value.

3. The apparatus of claim 2, wherein the controller is operative to select the predetermined period based on expected channel conditions.

4. The apparatus of claim 1, wherein the processor is operative to identify a largest energy among the energies of the plurality of rotated signals and to provide a hypothesized frequency error corresponding to the largest energy as the frequency error estimate.

5. The apparatus of claim 1, wherein the controller is operative to distribute the plurality of hypothesized frequency errors uniformly over a range of possible frequency errors.

6. The apparatus of claim 1, wherein the controller is operative to determine a range of possible frequency errors based on expected channel conditions and to select the plurality of hypothesized frequency errors based on the range of possible frequency errors.

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

8. The apparatus of claim 1, wherein the processor is operative to receive pilot symbols for the input signal.

9. The apparatus of claim 1, wherein the processor is operative to receive descrambled samples for the input signal.

10. A method comprising:

waking up from sleep to receive signaling during discontinuous reception (DRX) operation;

applying a plurality of hypothesized frequency errors to an input signal to obtain a plurality of rotated signals;

determining energies of the plurality of rotated signals;

determining a frequency error estimate based on the energies of the plurality of rotated signals;

using the frequency error estimate for detection of the signaling;

distributing the plurality of hypothesized frequency errors non-uniformly over a range of possible frequency errors and to use smaller frequency error spacing for at least one subrange of frequency errors with higher likelihood of containing an actual frequency error.

11. The method of claim 10, wherein the determining the energies of the plurality of rotated signals comprises

accumulating each rotated signal over a predetermined period to obtain an accumulated value for the rotated signal, and

computing energy of the accumulated value for each rotated signal.

12. The method of claim 10, wherein the determining the frequency error estimate comprises

identifying a largest energy among the energies of the plurality of rotated signals, and

providing a hypothesized frequency error corresponding to the largest energy as the frequency error estimate.

13. The method of claim 10, further comprising:

performing detection for a paging indicator sent at a predetermined time interval.

14. An apparatus comprising:

means for waking up from sleep to receive signaling during discontinuous reception (DRX) operation;

means for applying a plurality of hypothesized frequency errors to an input signal to obtain a plurality of rotated signals;

means for determining energies of the plurality of rotated signals;

means for determining a frequency error estimate based on the energies of the plurality of rotated signals;

means for using the frequency error estimate for detection of the signaling;

means for distributing the plurality of hypothesized frequency errors non-uniformly over a range of possible frequency errors and to use smaller frequency error spacing for at least one subrange of frequency errors with higher likelihood of containing an actual frequency error.

15. The apparatus of claim 14, wherein the means for determining the energies of the plurality of rotated signals comprises

means for accumulating each rotated signal over a predetermined period to obtain an accumulated value for the rotated signal, and

means for computing energy of the accumulated value for each rotated signal.

16. The apparatus of claim 14, wherein the means for determining the frequency error estimate comprises

means for identifying a largest energy among the energies of the plurality of rotated signals, and

means for providing a hypothesized frequency error corresponding to the largest energy as the frequency error estimate.

17. A computer program product, comprising:

a non-transitory computer-readable medium, comprising;

codes for causing a computer to wake up from sleep to receive signaling during discontinuous reception (DRX) operation;

codes for causing a computer to apply a plurality of hypothesized frequency errors to an input signal to obtain a plurality of rotated signals, to determine energies of the plurality of rotated signals, and to determine a frequency error estimate based on the energies of the plurality of rotated signals;

codes for causing a computer to use the frequency error estimate for detection of the signaling;

codes for causing a computer to distribute the plurality of hypothesized frequency errors non-uniformly over a range of possible frequency errors and to use smaller frequency error spacing for at least one subrange of frequency errors with higher likelihood of containing an actual frequency error.

18. A computer program product, comprising:

a non-transitory computer-readable medium, comprising;

codes for causing a computer to wake up from sleep to receive signaling during discontinuous reception (DRX) operation;

codes for causing a computer to apply a plurality of hypothesized frequency errors to an input signal to obtain a plurality of rotated signals;

codes for causing a computer to determine energies of the plurality of rotated signals;

codes for causing a computer to determine a frequency error estimate based on the energies of the plurality of rotated signals;

codes for causing a computer to use the frequency error estimate for detection of the signaling;

codes for causing a computer to distribute the plurality of hypothesized frequency errors non-uniformly over a range of possible frequency errors and to use smaller frequency error spacing for at least one subrange of frequency errors with higher likelihood of containing an actual frequency error.