Method of estimating doppler spread and signal-to-noise ratio of a received signal

• US 7,889,780 B2
• Filed: 01/02/2007
• Issued: 02/15/2011
• Est. Priority Date: 01/04/2006
• Status: Expired due to Fees

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: SIRF Technology Incorporated (Qualcomm, Inc.)
• Inventors: Leimer, Donald
• Primary Examiner(s): Wang; Ted M
• Application Number:
  US11/619,178
• Publication Number:
  US 20070183485A1
• Time in Patent Office: 1,505 Days
• Field of Search: 375/147, 375/346, 375/354, 375/136, 375/142, 375/150, 375/316
• US Class Current: 375/147
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04L 27/261 Details of reference signals

Abstract

A method for estimating a Doppler spread and a signal-to-noise ratio of a received signal includes: (a) calculating one or more functions of a carrier component of the received signal at a first time point relative to a pilot signal embedded in the received signal; (b) Calculating the one or more functions of the carrier component of the received signal at a second time point relative to the pilot signal; (c) repeating steps (a) and (b) over multiple time periods, each time period being substantially longer than the second time, and accumulating the one or more functions for the first time points and the second time points; and (d) Deriving the Doppler spread and the signal-to-noise ration based on the accumulated one or more functions calculated at the first and second time points. In one embodiment, the first time point is substantially closer to the pilot signal than the second time point. The first time point is one symbol interval from the pilot signal.

Claims

1. A method for estimating a Doppler spread and a signal-to-noise ratio of a signal, comprising:

(a) Receiving the signal in a receiver to determine a carrier component of the signal;

(b) Calculating loss in coherence of the carrier component at a first time point relative to a pilot signal embedded in the received signal;

(c) Calculating loss in coherence of the carrier component of the received signal at a second time point relative to the pilot signal;

(d) Repeating steps (b) and (c) over multiple time periods, each time period being longer than the second time, and accumulating the loss in coherence for the first time points and the second time points; and

(e) Deriving the Doppler spread and the signal-to-noise ratio based on the accumulated loss in coherence calculated at the first and second time points.

2. A method as in claim 1, wherein the first time point is substantially closer to the pilot signal than the second time point.

3. A method as in claim 2, wherein the first time point is one symbol interval from the pilot signal.

4. The method of claim 1, wherein a product of the Doppler spread and the time difference between the first time point and the second time point is a positive value.

5. The method of claim 4, wherein the positive value is approximately 0.25.

6. The method of claim 4, wherein the positive value is less than or equal to 1.0.

7. The method of claim 1, wherein calculating the loss in coherence comprises an even-symmetric linearity function of a sum of the carrier component and the pilot signal.

8. The method of claim 1, wherein calculating the loss in coherence comprises an even-symmetric linearity of a difference between the carrier component and the pilot signal.

9. The method of claim 1, wherein calculating the loss in coherence comprises an even-symmetric linearity of an absolute value function.

10. The method of claim 1, wherein calculating the loss in coherence comprises an even-symmetric linearity of a squaring function.

11. The method of claim 1, wherein the time domain representation of the received signal comprises a sum of the transmitted signal and noise.

12. The method of claim 1, wherein the received signal is modeled as a Rayleigh faded continuous wave signal.

13. The method of claim 1, wherein the loss in coherence is provided by Jake'"'"'s model.

14. A method for estimating doppler spread and signal-to-noise ratio, comprising:

means for receiving a signal and for determining a carrier component of the signal;

means for calculating loss in coherence of the carrier component at a first time point relative to the pilot signal;

means for calculating loss in coherence of the carrier component at a second time point relative to the pilot signal;

means for calculating an accumulated loss in coherence for the first time point and the second time point over a period of time intervals; and

means for deriving the doppler spread and signal-to-noise ratio based on the accumulated loss in coherence.

15. The method of claim 14, further comprising means for selecting an optimum value for reception based on the derived Doppler spread and signal-to-noise ratio.

16. The method of claim 14, further comprising means for determining the first time point that is substantially closer to the pilot signal than the second time point.

17. The method of claim 14, further comprising means for determining the loss in coherence by an even-symmetric linearity function.

18. The method of claim 14, further comprising means for receiving a signal modeled as a Rayleigh faded continuous wave.

19. The method of claim 14, further comprising means for determining loss in coherence provided by Jake'"'"'s model.