Doppler spread estimation system

• US 6,563,861 B1
• Filed: 03/22/1999
• Issued: 05/13/2003
• Est. Priority Date: 03/22/1999
• Status: Expired due to Term

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Koilpillai, David, Krasny, Leonid, Chennakeshu, Sandeep
• Primary Examiner(s): PHU, PHUONG M
• Application Number:
  US09/273,480
• Time in Patent Office: 1,513 Days
• Field of Search: 375/142, 375/144, 375/147, 375/148, 375/150, 375/224, 375/226, 375/343, 375/346, 375/349, 375/267, 702/77, 714/714
• US Class Current: 375/150
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/709 Correlator structure
• CPC Class Codes: H04B 2201/70701 featuring pilot assisted reception
• CPC Class Codes: H04B 7/01 Reducing phase shift

Abstract

A receiving apparatus Doppler spread estimator includes a receiver receiving signals over a transmission channel that varies over time due to fading and converting the signals to digital samples for processing. A stationarizer operatively associated with the receiver stationarizes the digital samples. An estimator is operatively associated with the stationarizer for estimating spectral density of the stationarized digital samples. The correlator is operatively coupled to the estimator for correlating the spectral density estimates with functions corresponding to hypotheses of plural Doppler spread values to select one of the Doppler spread values as an estimate of actual Doppler spread.

Claims

1. A Doppler spread estimator comprising:

receive means for receiving signals over a transmission channel that varies over time due to fading and converting the signals to digital samples for processing, wherein said received signals represent a sequence of transmitted symbols;

first processing means operatively associated with the receive means for estimating spectral densities of the digital samples;

second processing means operatively coupled to the first processing means for correlating the spectral density estimates with functions corresponding to hypotheses of plural Doppler spread values to select one of said Doppler spread values as an estimate of actual Doppler spread; and

third processing means comprising a multiplier for mixing the digital samples with a complex conjugate of the transmitted symbols, the third processing means being operatively associated with the receive means for stationarizing the digital samples prior to estimating spectral densities of the digital samples.

2. The Doppler spread estimator of claim 1 wherein said receive means is adapted to receive Code-Division Multiple Access (CDMA) signals.

3. The Doppler spread estimator of claim 2 wherein channel coefficients are directly obtained from the CDMA signals.

4. The Doppler spread estimator of claim 1 wherein said receive means is adapted to receive signals including pilot symbols spread with a known CDMA spreading code.

5. The Doppler spread estimator of claim 1 wherein said complex conjugate of the transmitted symbols is derived from a symbol estimator.

6. The Doppler spread estimator of claim 1 wherein said third processing means further comprises a low pass filter.

7. The Doppler spread estimator of claim 1 wherein said first processing means develops vector data representing spectral components.

8. The Doppler spread estimator of claim 1 wherein said second processing means comprises a multichannel correlator.

9. The Doppler spread estimator of claim 8 wherein said correlator calculates correlations between estimated spectral densities and weighting functions corresponding to the hypotheses of the plural Doppler spread values.

10. The Doppler spread estimator of claim 9 wherein the second processing means includes a selector for selecting the hypothesis producing a highest correlation value.

11. A receiving apparatus Doppler spread estimator comprising:

a receiver receiving signals over a transmission channel that varies over time due to fading and converting the signals to digital samples for processing, wherein said received signal represents a sequence of transmitted symbols;

an estimator operatively associated with a stationarizer for estimating spectral densities of stationarized digital samples;

a correlator operatively coupled to the estimator for correlating the spectral density estimates with functions corresponding to hypotheses of plural Doppler spread values to select one of said Doppler spread values as an estimate of actual Doppler spread; and

a stationarizer, comprising a multiplier for mixing the digital samples with a complex conjugate of the transmitted symbols, the stationarizer operatively associated with the receiver for stationarizing the digital samples prior to estimating spectral densities of the digital samples.

12. The receiving apparatus Doppler spread estimator of claim 11 wherein said receiver is adapted to receive Code-Division Multiple Access (CDMA) signals.

13. The Doppler spread estimator of claim 12 wherein channel coefficients are directly obtained from the CDMA signals.

14. The receiving apparatus Doppler spread estimator of claim 11 wherein said receiver is adapted to receive signals including pilot symbols spread with a known CDMA spreading code.

15. The receiving apparatus Doppler spread estimator of claim 11 wherein said complex conjugate of the transmitted symbols is derived from a symbol estimator.

16. The receiving apparatus Doppler spread estimator of claim 11 wherein said stationarizer further comprises a low pass filter.

17. The receiving apparatus Doppler spread estimator of claim 11 wherein said estimator develops vector data representing spectral components.

18. The receiving apparatus Doppler spread estimator of claim 11 wherein said correlator comprises a multichannel correlator.

19. The receiving apparatus Doppler spread estimator of claim 18 wherein said correlator calculates correlations between estimated spectral densities and weighting functions corresponding to the hypotheses of the plural Doppler spread values.

20. The receiving apparatus Doppler spread estimator of claim 19 wherein the correlator includes a selector for selecting the hypothesis producing a highest correlation value.

21. The method of estimating Doppler spread of a received signal, comprising the steps of:

receiving the signals over a transmission channel that varies over time due to fading and converting-the signals to digital samples for processing, wherein said received signal represents a sequence of transmitted symbols;

stationarizing the digital samples by multiplying the digital samples with a complex conjugate of the transmitted symbols;

estimating spectral densities of stationarized digital samples; and

correlating the spectral density estimates with functions corresponding to hypotheses of plural Doppler spread values to select one of said Doppler spread values as an estimate of actual Doppler spread.

22. The method of claim 21 wherein said receiving step receives Code Division Multiple Access signals.

23. The Doppler spread estimator of claim 22 wherein channel coefficients are directly obtained from the CDMA signals.

24. The method of claim 21 wherein said receiving step receives signals including pilot symbols spread with a known CDMA spreading code.

25. The method of claim 21 wherein said complex conjugate of the transmitted symbols is derived from a symbol estimator.

26. The method of claim 21 wherein said stationarizing step comprises low pass filtering the mixed samples.

27. The method of claim 21 wherein said estimating step develops vector data representing spectral components.

28. The method of claim 21 wherein said correlating step comprises using a multichannel correlator.

29. The method of claim 28 wherein said correlator calculates correlations between estimated spectral densities and weighting functions corresponding to the hypotheses of the plural Doppler spread values.

30. The method of claim 29 wherein the correlating step includes selecting the hypothesis producing a highest correlation value.