Doppler spread/velocity estimation in mobile wireless communication devices and methods therefor

• US 6,636,574 B2
• Filed: 05/31/2001
• Issued: 10/21/2003
• Est. Priority Date: 05/31/2001
• Status: Expired due to Fees

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Oliver, John Paul, Mallette, Alexandre
• Primary Examiner(s): Tran, Khai
• Application Number:
  US09/871,116
• Publication Number:
  US 20020181553A1
• Time in Patent Office: 873 Days
• Field of Search: 375/360, 375/142, 375/144, 375/148, 375/150, 375/224, 375/343, 375/346, 342/104, 342/105, 342/357.05, 342/418, 342/717, 342/405, 455/441, 455/67.6
• US Class Current: 375/360
• CPC Class Codes: H04L 25/0202 Channel estimation

Abstract

A method for estimating Doppler spread in mobile wireless communication devices, for example in CDMA or W-CDMA cellular communication systems, with improved noise immunity. The Doppler spread estimation is based on an estimated value of an autocorrelation or autocovariance at a first lag (210) and at a second lag (220), the magnitude of which is greater than the first lag. A first ratio is determined (250) between a first difference (230) and a second difference (240). The estimated Doppler spread is generally proportional to a square root (260) of the first ratio, and is scaled (270) by a multiplicative factor that depends on whether the estimated function is an autocorrelation or autocovariance function.

Claims

1. A method for estimating Doppler spread in a mobile wireless communication device, comprising:

estimating a value of an estimated autocorrelation of an impulse response of a channel for first and second lags, the second lag having a magnitude greater than a magnitude of the first lag;

determining a first ratio between a first difference and a second difference,

the first difference is a difference between the estimated value at the first lag and the estimated value at the second lag,

the second difference is a difference between a first product and a second product, the first product is a product of the second lag squared and the estimated value at the first lag, the second product is a product of the first lag squared and the estimated value at the second lag;

determining a square root of the first ratio if the first ratio is greater than zero;

determining Doppler spread proportional to the square root of the first ratio.

2. The method of claim 1, determining a square root of an absolute value of the first ratio if the first ratio is less than zero.

3. The method of claim 1, setting the value of the first ratio to zero if the first ratio is less than zero.

4. The method of claim 1, determining the Doppler spread by multiplying the square root of the first ratio by a second ratio, the second ratio is a reciprocal of a product of π

and T, where T is an inverse processing rate.

5. The method of claim 1, estimating the autocorrelation from both in-phase and quadrature components of a signal.

6. The method of claim 1, estimating the autocorrelation from one of an in-phase and quadrature component of a signal.

7. A method for estimating Doppler spread in a mobile wireless communication device, comprising:

estimating a value of an estimated autocovariance of a magnitude squared of an impulse response of a channel for a first non-zero lag and for a second lag, the second lag having a magnitude greater than a magnitude of the first lag;

determining a first ratio between a first difference and a second difference,

the first difference is a difference between the estimated value at the first lag and the estimated value at the second lag,

the second difference is a difference between a first product and a second product, the first product is a product of the second lag squared and the estimated value at the first lag, the second product is a product of the first lag squared and the estimated value at the second lag;

determining a square root of the first ratio if the first ratio is greater than zero;

determining Doppler spread proportional to the square root of the first ratio.

8. The method of claim 7, determining a square root of an absolute value of the first ratio if the first ratio is less than zero.

9. The method of claim 7, setting the value of the first ratio to zero if the first ratio is less than zero.

10. The method of claim 7, determining the Doppler spread by multiplying the square root of the first ratio by a second ratio, the second ratio is a ratio of the square root of 2 divided by a product of 2π

and T, where T is an inverse processing rate.

11. A mobile wireless communication device, comprising:

means for determining a square root of a first ratio greater than zero,

the first ratio defined by [φ

(n)−

φ

(m)]/[m²φ

(n)−

n²φ

(m)],

where φ

(n) is an estimated value of an estimated autocorrelation of an impulse response of a channel at a first lag, n, φ

(m) is an estimated value of the estimated autocorrelation at a second lag, m,

a magnitude of the second lag m greater than a magnitude of first lag n;

means for determining Doppler spread proportional to a square root of the first ratio if the first ratio is greater than zero.

12. The device of claim 11, means for determining a square root of an absolute value of the first ratio if the first ratio is less than zero.

13. The device of claim 11, means for setting the value of the first ratio to zero if the first ratio is less than zero.

14. The device of claim 11, means for scaling the square root of the first ratio by a multiplicative factor of the reciprocal of a product of π

and T, where T is the inverse of a processing rate.

15. The device of claim 11, a rake receiver having a plurality of rake fingers, means for estimating the autocorrelation from an output of one or more of the plurality of rake fingers.

16. The device of claim 11, means for estimating the autocorrelation from both in-phase and quadrature components of a received signal.

17. The device of claim 11, means for estimating the autocorrelation from one of an in-phase or a quadrature component of a received signal.

18. A mobile wireless communication device, comprising:

means for determining a square root of a first ratio greater than zero,

the first ratio defined by [φ

(n)−

φ

(m)]/[m²φ

(n)−

n²φ

(m)],

where φ

(n) is an estimated value of an estimated autocovariance from a magnitude squared of an impulse response of a channel at a first non-zero lag, n,

φ

(m) is an estimated value of the estimated autocovariance at a second lag, m,

a magnitude of the second lag m greater than a magnitude of first lag, n;

means for determining Doppler spread proportional to a square root of the first ratio if the first ratio is greater than zero.

19. The device of claim 18, means for scaling the square root of the first ratio by a multiplicative factor of the square root of 2 divided by a product of 2π

T, where T is the inverse of a processing rate.

20. The device of claim 18, a rake receiver, means for estimating the autocovariance from an output of the rake receiver.

21. The device of claim 18, a rake receiver having a plurality of rake fingers, means for estimating the autocovariance from an output of one or more of the plurality of rake fingers.

22. The device of claim 18, means for estimating the autocovariance from both in-phase and quadrature components of a received signal.

23. The device of claim 18, means for determining a square root of an absolute value of the first ratio if the first ratio is less than zero.

24. The device of claim 18, means for setting the value of the first ratio to zero if the first ratio is less than zero.