METHOD OF PROVIDING A DATA SIGNAL FOR CHANNEL ESTIMATION AND CIRCUIT THEREOF

• US 20080304605A1
• Filed: 07/31/2008
• Published: 12/11/2008
• Est. Priority Date: 10/31/2006
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Dehner, Leo G., Aziz, Ahsan U.
• Granted Patent: US 8,014,457 B2
• Time in Patent Office: Days
• US Class Current: 375/347
• CPC Class Codes: H04L 25/0216 with estimation of channel length
• CPC Class Codes: H04L 25/0232 by interpolation between sounding signals
• CPC Class Codes: H04L 27/2605 Symbol extensions, e.g. Zero Tail, Unique Word [UW]
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01

Abstract

A received signal having pilots is converted to a first signal in the frequency domain having the pilots. The pilots are extracted from the first signal to obtain extracted pilots to form a second signal. The second signal is used to provide a first estimate of a channel. The first estimate is converted to the time domain. Noise is removed from the first estimate in the time domain to provide a second estimate of the channel in the time domain. An autocorrelation of the channel in the frequency domain is determined using the second estimate of the channel. Extension signals are determined using the autocorrelation. The extension signals are appended to the first estimate of the channel to obtain a third estimate of the channel. The third estimate is used to provide a data signal in the frequency domain.

Claims

1. A method of providing a data signal in a frequency domain corrected for distortion, comprising:

converting a received signal having pilots to a first signal having the pilots in the frequency domain;

extracting the pilots from the first signal to obtain extracted pilots to form a second signal;

using the second signal to provide a first estimate of a channel;

converting the first estimate to the time domain;

removing noise from the first estimate in the time domain to provide a second estimate of the channel in the time domain;

determining an autocorrelation of the channel in the frequency domain using the second estimate of the channel;

determining extension signals using the autocorrelation;

appending the extension signals to the first estimate of the channel to obtain a third estimate of the channel; and

using the third estimate to provide the data signal in the frequency domain.

2. The method of claim 1, wherein the step of using the third estimate comprises:

converting the third estimate of the channel to the time domain to provide a fourth estimate of the channel;

removing noise from the fourth estimate;

performing zero insertion on the fourth estimate to obtain an interpolation ready signal;

performing a fast Fourier transform on the interpolation ready signal whereby, in the frequency domain, interpolation occurs which provides channel information among the pilots and provides extended channel information in locations determined using the extension signals to provide a sixth estimate of the channel;

removing the extension signals and the extended channel information from the sixth estimate to provide a seventh estimate of the channel; and

dividing the first signal by the seventh estimate to provide the data signal.

3. The method of claim 2, wherein the step of converting the third estimate comprises performing an inverse fast Fourier transform.

4. The method of claim 1, wherein the step of determining the extension signals, comprises:

determining filter coefficients of a minimum mean square error (MMSE) filter using the autocorrelation; and

performing MMSE filtering on a portion of the first estimate of the channel using the filter coefficients to determine the extension signals.

5. The method of claim 1, wherein the step of determining the autocorrelation comprises:

performing a tap selection on the second estimate; and

determining a channel delay spread based on the tap selection.

6. The method of claim 5, wherein the step of determining the autocorrelation assumes a uniformly distributed power delay profile.

7. The method of claim 5, wherein the step of determining the autocorrelation further comprises using the channel delay spread to calculate the autocorrelation.

8. The method of claim 1, wherein:

the step of using the second signal is further characterized by obtaining a least square estimate.

9. The method of claim 1, wherein:

the step of extracting the pilots is further characterized as providing a number of extracted pilots; and

the step of determining extension signals is further characterized as providing a length of extension signals that when added to the length of least square estimates obtained form the extracted pilots equals a number that is a power of an integer.

10. The method of claim 9, wherein the step of determining extension signals is further characterized by the integer being two.

11. The method of claim 9, wherein the step of using the third estimate comprises:

performing an inverse fast Fourier transform; and

performing a fast Fourier transform.

12. The method of claim 1, further comprising:

generating a first frequency domain signal having pilots;

converting the first frequency domain signal to a first time domain signal;

transmitting the first time domain signal using a transmit antenna; and

receiving the first time domain signal through a receive antenna, wherein the first time domain signal as received through the receive antenna is distorted by the channel and is the received signal.

13. A method of providing a resultant frequency domain signal based on a time domain signal having pilots useful in estimating a channel through which the time domain signal traveled, comprising:

obtaining an input frequency domain signal derived from the time domain signal;

providing a first estimate of the channel using pilots from the input frequency domain signal;

determining an autocorrelation based on the first estimate of the channel;

adding extension signals to the first estimate of the channel based on the autocorrelation to obtain a second estimate of the channel;

using, which includes performing an inverse fast Fourier transform and a fast Fourier transform, the second estimate of the channel to obtain a third estimate of the channel; and

using the third estimate of the channel on the input frequency domain signal to provide the resultant frequency domain signal.

14. The method of claim 13, wherein the step of determining the autocorrelation comprises:

determining a power delay profile of the channel based on the first estimate; and

calculating the autocorrelation based on the power delay profile.

15. The method of claim 13, wherein the step of determining the autocorrelation comprises:

determining a channel delay spread based on the first estimate; and

calculating the autocorrelation based on the channel delay spread.

16. The method of claim 15, wherein the step of adding the extension signals comprises:

calculating minimum mean square error (MMSE) filter coefficients using the autocorrelation; and

performing MMSE interpolation using the MMSE filter coefficients to determine the extension signals.

17. The method of claim 13, wherein the step of adding extension signal is further characterized by a total the length of least square estimate and the extension signals being equal to a number that is a power of an integer.

18. A circuit for providing a resultant frequency domain signal in response to a time domain signal having pilots useful in estimating a channel through which the time domain signal traveled, comprising:

means for obtaining an input frequency domain signal derived from the time domain signal;

means for providing a first estimate of the channel using pilots from the input frequency domain signal;

means for determining an autocorrelation based on the first estimate of the channel;

means for adding extension signals to the first estimate of the channel based on the autocorrelation to obtain a second estimate of the channel;

means for using, which includes performing an inverse fast Fourier transform and a fast Fourier transform, the second estimate of the channel to obtain a third estimate of the channel; and

means for using the third estimate of the channel on the input frequency domain signal to provide the resultant frequency domain signal.

19. The circuit of claim 18, wherein the means for determining the autocorrelation is further characterized as being for determining a channel delay spread and calculating the autocorrelation based on the channel delay spread.

20. The circuit of claim 19, wherein the means for adding extension signals is further characterized as being for calculating minimum mean square estimate (MMSE) filter coefficients using the autocorrelation and for performing MMSE interpolation using the MMSE filter coefficients to obtain the extension signals.