CDMA pilot assisted channel estimation

• US 7,149,264 B2
• Filed: 04/08/2005
• Issued: 12/12/2006
• Est. Priority Date: 06/14/2004
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Black, Peter J., Xu, Hao, Namgoong, June, Jayaraman, Srikant
• Primary Examiner(s): Bayard, Emmanuel
• Application Number:
  US11/102,301
• Publication Number:
  US 20050276364A1
• Time in Patent Office: 613 Days
• Field of Search: 375/316, 375/340, 375/347, 375/349, 375/130, 375/136, 370/320, 370/335, 370/342, 370/441, 370/208
• US Class Current: 375/349
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 25/0216 with estimation of channel length
• CPC Class Codes: H04L 25/0234 by non-linear interpolation

Abstract

A pilot assisted channel estimation process. A receiver may be configured to estimate the impulse response of a channel from a signal having pilot tones and spread-spectrum pilot signals. The receiver estimates the response of the channel from the pilot tones, and adapts the length of delay the channel response is estimated based on the spread-spectrum pilot signals.

Claims

1. A method of channel estimation, comprising:

receiving a signal from a multipath fading channel, the signal including a plurality of pilot tones;

deriving timing information for a plurality of multipath signal arrivals;

estimating the response of the channel from the pilot tones; and

adapting the length of delay the channel response is estimated from the timing information for the multipath signal arrivals.

2. The method of claim 1 wherein the signal further includes a plurality of spread-spectrum pilot signals, the timing information for the mulitpath signal arrivals being derived from the spread-spectrum pilot signals.

3. The method of claim 2 wherein the signal further comprises Orthogonal Frequency Division Multiplexing (OFDM) data punctured into spread-spectrum data, the method further comprising synchronizing the processing the OFDM data based on the timing information for the multipath signal arrivals.

4. The method of claim 1 wherein the timing information used to adapt the length of time the channel response is estimated includes timing information for the earliest multipath signal arrival and the latest multipath signal arrival.

5. The method of claim 4 wherein the length of time the channel response is estimated is adapted to equal the delay between the earliest multipath signal arrival and the latest multipath signal arrival.

6. The method of claim 5 wherein the length of time the channel response is estimated is adapted by adjusting the delay to account for delay dispersion introduced by one or more pulse-shaping filters.

7. The method of claim 4 wherein the length of time the channel response is estimated is adapted by determining that the delay between the earliest multipath signal arrival and the latest signal path arrival exceeds the minimum delay, and adapting the length of time to estimate the channel response to the larger of the estimated length and the minimum delay.

8. The method of claim 4 wherein the length of time the channel response is estimated is adapted by determining that the delay between the earliest multipath signal arrival and the latest signal path arrival is below the maximum delay, and adapting the length of time to estimate the channel response to the smaller of the estimated length and the maximum delay, the maximum delay being a function of the number of pilot tones.

9. A method of channel estimation, comprising:

receiving a signal including a plurality of pilot tones and spread-spectrum pilot signals;

estimating the response of the channel from the pilot tones; and

adapting the length of time the channel response is estimated based on the spread-spectrum pilot signals.

10. The method of claim 9 wherein the signal further comprises OFDM data punctured into spread-spectrum data, the method further comprising synchronizing the processing of the spread-spectrum data based on timing information derived from the spread-spectrum pilot signals.

11. The method of claim 9 wherein the channel is a multipath fading channel, the method further comprising deriving timing information for a plurality of multipath signal arrivals from the spread-spectrum pilot signals, the timing information for the multipath signal arrivals being used to adapt the length of time the channel response is estimated.

12. The method of claim 11 wherein the timing information used to adapt the length of time the channel response is estimated includes timing information for the earliest multipath signal arrival and the latest multipath signal arrival.

13. The method of claim 12 wherein the length of time the channel response is estimated is adapted to equal the delay between the earliest multipath signal arrival and the latest multipath signal arrival.

14. The method of claim 13 wherein the length of time the channel response is estimated is adapted by adjusting the delay to account for delay dispersion introduced by one or more pulse-shaping filters.

15. The method of claim 12 wherein the length of time the channel response is estimated is adapted by determining that the delay between the earliest multipath signal arrival and the latest signal path arrival exceeds a maximum delay, and adapting the length of time to estimate the channel response to the maximum delay, the maximum delay being a function of the number of pilot tones.

16. The method of claim 12 wherein the length of time the channel response is estimated is adapted by determining that the delay between the earliest multipath signal arrival and the latest signal path arrival is below a minimum delay, and adapting the length of time to estimate the channel response to the minimum delay.

17. A receiver, comprising:

a rake receiver configured to derive timing information from a signal transmitted over a multipath fading channel, the timing information relating to a plurality of multipath signal arrivals; and

a demodulator configured to extract a plurality of pilot tones from the signal, the demodulator including a channel estimator having a delay spread capable of being adapted by the timing information from the rake receiver, the channel estimator being configured to estimate the response of the channel from the pilot tones.

18. The receiver of claim 17 wherein the rake receiver is further configured to derive the timing information from a plurality of spread-spectrum pilot signals in the signal.

19. The receiver of claim 18 wherein the demodulator is further configured to process OFDM data punctured into the signal, the processing of the OFDM data being synchronized by the timing information relating to the multipath arrivals.

20. The receiver of claim 17 wherein the timing information generated by the rake receiver includes timing information for the earliest multipath signal arrival and the latest multipath signal arrival.

21. The receiver of claim 20 wherein the channel estimator is further configured to compute the delay between the earliest multipath signal arrival and the latest multipath signal arrival, and adapt the delay spread to the computed delay if the computed delay is within a range.

22. The receiver of claim 21 wherein the channel estimator is further configured to account for delay dispersion introduced by one or more pulse-shaping filters when computing the delay.

23. The receiver of claim 21 wherein the range has a maximum delay that is a function of the number of pilot tones, the channel estimator being further configured to adapt the delay spread to the maximum delay if the computed delay exceeds the maximum delay.

24. The receiver of claim 21 wherein the range has a minimum delay, the channel estimator being further configured to adapt the delay spread to the minimum delay if the computed delay is below the maximum delay.

25. A receiver, comprising:

a rake receiver configured to derive timing information from a plurality of spread-spectrum pilot signals in a signal transmitted over a channel; and

a demodulator configured to extract a plurality of pilot tones from the signal, the demodulator including a channel estimator having a delay spread capable of being adapted by the timing information from the rake receiver, the channel estimator being configured to estimate the response of the channel from the pilot tones.

26. The receiver of claim 25 wherein the demodulator is further configured to process OFDM data punctured into the signal, the processing of the OFDM data being synchronized by the timing information derived from the spread-spectrum pilot signals.

27. The receiver of claim 25 wherein the channel is a multipath fading channel, and the timing information relates to a plurality of multipath signal arrivals.

28. The receiver of claim 27 wherein the timing information generated by the rake receiver includes timing information for the earliest multipath signal arrival and the latest multipath signal arrival.

29. The receiver of claim 28 wherein the channel estimator is further configured to compute the delay between the earliest multipath signal arrival and the latest multipath signal arrival, and adapt the delay spread to the computed delay if the computed delay is within a range.

30. The receiver of claim 29 wherein the channel estimator is further configured to account for delay dispersion introduced by one or more pulse-shaping filters when computing the delay.

31. The receiver of claim 29 wherein the range has a maximum delay that is a function of the number of pilot tones, the channel estimator being further configured to adapt the delay spread to the maximum delay if the computed delay exceeds the maximum delay.

32. The receiver of claim 29 wherein the range has a minimum delay, the channel estimator being further configured to adapt the delay spread to the minimum delay if the computed delay is below the maximum delay.