Granted Patent B2

US 7,684,504 · App. 11/589,877 · Granted Mar 23, 2010

Abstract

Claims (67)

1. A channel estimator, comprising:

an extension circuit configured to receive a pilot signal, to add a front extension signal to a front of the pilot signal, and to add a back extension signal to a back of the pilot signal, to create a first intermediate signal, the front extension signal being an extension of a first symbol in the pilot signal, and the back extension signal being an extension of a last symbol in the pilot signal;

an inverse discrete Fourier transform circuit configured to perform an inverse discrete Fourier transform function on the first intermediate signal to generate a second intermediate signal;

a signal processing element configured to perform one or more operations on the second intermediate signal to generate a third intermediate signal;

a discrete Fourier transform circuit configured to perform a discrete Fourier transform function on the third intermediate signal to generate a fourth intermediate signal; and

a reduction circuit configured to truncate a front end of the fourth intermediate signal and a back end of the fourth intermediate signal to generate a channel estimation signal.

2. The channel estimator of claim 1 , wherein the signal processing element comprises a zero insertion circuit configured to split the second intermediate signal in half, and to insert a zeroed signal having an amplitude of approximately zero between the a front half and a back half of the second intermediate signal to create the third intermediate signal.

3. The channel estimator of claim 1 , wherein the signal processing element comprises a non-linear filter for performing a filtering operation on the second intermediate signal to generate the third intermediate signal.

4. The channel estimator of claim 3 , further comprising:

a noise estimator configured to provide an estimation of a noise level in a received signal; and

a threshold set circuit configured to provide threshold level to control the operation of the filter based on the estimation of noise level.

5. The channel estimator of claim 1 , wherein the signal processing element comprises:

a filter for performing a filtering operation on the second intermediate signal to generate a fifth intermediate signal;

a zero insertion circuit configured to split the fifth intermediate signal in half, and to insert a zeroed signal having an amplitude of approximately zero between the a front half and a back half of the fifth intermediate signal to create the third intermediate signal.

6. The channel estimator of claim 5 , wherein when the filtering operation comprises:

setting all points in a front portion of the fifth intermediate signal that are below a noise threshold to a zero or near-zero value,

setting all points in an end portion of the fifth intermediate signal that are below the noise threshold to a zero or near-zero value, and

setting all points in a middle portion of the fifth intermediate signal between the front portion and the end portion to a zero or near-zero value.

7. The channel estimator of claim 1 , wherein when the front extension signal is concatenated to the end of the back extension signal, a resulting concatenated signal is a continuous differentiable function.

8. The channel estimator of claim 1 ,

wherein a symbol length of the first intermediate signal is a power of 2, and

wherein the inverse discrete Fourier transform circuit is an inverse fast Fourier transform circuit.

9. The channel estimator of claim 1 ,

wherein a symbol length of the third intermediate signal is a power of 2, and

wherein the discrete Fourier transform circuit is a fast Fourier transform circuit.

10. The channel estimator of claim 1 , wherein the channel estimator is implemented in one of an integrated circuit or software.

11. A method of estimating a channel response, comprising:

receiving a pilot signal comprising a series of pilot symbols;

adding a front extension signal comprising one or more front symbols to a front of the pilot signal and a back extension signal comprising one or more back symbols to a back of the pilot signal at an extension circuit, to create a first intermediate signal;

performing an inverse discrete Fourier transform function on the first intermediate signal to generate a second intermediate signal;

performing one or more signal processing operations on the second intermediate signal in a signal processing circuit to generate a third intermediate signal;

performing a discrete Fourier transform function on the third intermediate signal to generate a fourth third intermediate signal; and

cutting off a front end of the fourth third intermediate signal and a back end of the fourth third intermediate signal in a reduction circuit to generate a channel estimation signal,

wherein the front extension signal is differentiable at all points of interest in the front extension signal and at a transition between the front extension signal and the pilot signal, and

wherein the back extension signal is differentiable at all points of interest in the back extension signal and at a transition between the back extension signal and the pilot signal.

12. The method of claim 11 , wherein the performing of one or more signal processing operations comprises:

splitting the first intermediate channel signal in half to form a first signal half and a second signal half and

inserting a zeroed signal having an amplitude of zero or approximately zero between the first signal half and the second signal half to create the third intermediate signal.

13. The method of estimating a channel response, as recited in claim 11 , further comprising performing a non-linear filtering operation on the first intermediate channel signal before the inserting of a zeroed signal.

14. The method of estimating a channel response, as recited in claim 13 , further comprising:

determining an estimation of a noise level in a received signal containing the pilot signal; and

setting a threshold level to control the filtering operation based on the estimation of noise level.

15. The method of estimating a channel response, as recited in claim 11 ,

wherein the front extension signal is a first essentially flat linear signal having a first constant value equal to a first value in the pilot signal, and

wherein the back extension signal is a second essentially flat linear signal having a second constant value equal to a last value in the pilot signal.

16. The method of estimating a channel response, as recited in claim 11 , wherein when the front extension signal is concatenated to the end of the back extension signal, a resulting concatenated signal is a continuous differentiable function.

17. The method of estimating a channel response, as recited in claim 11 , wherein the method is implemented in one of an integrated circuit or software.

18. A method of estimating a channel response, comprising:

receiving an initial channel signal comprising a series of P pilot symbols;

adding a front extension signal comprising a series of F front symbols to a front of the initial channel signal;

adding a back extension signal comprising a series of B back symbols to a back of the initial channel signal, to create an extended channel signal;

performing an inverse discrete Fourier transform function on the extended channel signal at a sampling length of (P+F+b) to generate a first intermediate channel signal;

splitting the first intermediate channel signal in half in a zero insertion circuit;

inserting a signal having an effective length of Z symbols and an amplitude of zero or approximately zero between the two halves of the first intermediate channel signal in the zero insertion circuit to create an expanded channel signal;

performing a discrete Fourier transform function on the expanded channel signal at a sampling length of (P+F+b+Z) to generate a second intermediate channel signal; and

cutting off a front end of the second intermediate channel signal and a back end of the second intermediate channel signal in a reduction circuit to generate a channel estimation signal of length D,

wherein B, D, F, P, and Z are all integers and F and B are both greater than 1,

wherein P identifies a number of pilot symbols in one data slot, and D identifies a number of data symbols in one data slot,

wherein the P pilot symbols, the F front symbols, and the B back symbols are all selected from a constellation of available symbols,

wherein the F front symbols are selected to be differentiable at all points of interest over the F front symbols and at a transition between the front extension signal and the initial channel signal, and

wherein the B back symbols are selected to be differentiable at all points of interest over the B back symbols and at a transition between the back extension signal and the initial channel signal.

19. The method of estimating a channel response, as recited in claim 18 ,

wherein the F front symbols are selected to be the same as the first pilot symbol in the P pilot, and

wherein the B back symbols are selected to be the same as the last pilot symbol in the P pilot symbols.

20. The method of estimating a channel response, as recited in claim 18 ,

wherein the F front symbols and the B back symbols have values based on a continuous function that bridges the first and the last sample of the original data,

wherein a continuous function is one that is differentiable at all point of interest.

Assignments (37)