Equalization of a distributed pilot OFDM signal

1. A method comprising:

at a receiver, coarsely correlating a received orthogonal frequency division multiplexed (OFDM) signal against a pilot reference to obtain a coarse channel estimate, the received OFDM signal comprising a distributed pilot signal and an OFDM data signal;

coarsely equalizing the received OFDM signal based on the coarse channel estimate;

removing the distributed pilot signal from the received OFDM signal after coarsely equalizing to generate a coarse data signal estimate;

removing the coarse data signal estimate from the received OFDM signal using the coarse channel estimate to generate a residual pilot signal;

finely correlating the residual pilot signal against the pilot reference to obtain a fine channel estimate;

finely equalizing the received OFDM signal based on the fine channel estimate; and

removing the distributed pilot signal from the received OFDM signal after fine equalization to generate a fine data signal estimate from which data is recoverable.

2. The method of claim 1 , wherein coarsely equalizing the received OFDM signal based on the coarse channel estimate comprises:

converting the received OFDM signal to a frequency domain signal;

constructing a coarse zero forcing function from the coarse channel estimate; and

applying the coarse zero forcing function to the frequency domain signal.

3. The method of claim 2 , wherein removing the distributed pilot signal from the OFDM signal coarsely equalized based on the coarse channel estimate comprises removing the distributed pilot signal from the frequency domain signal after equalizing the received OFDM signal with the coarse zero forcing function.

4. The method of claim 2 , wherein generating the coarse data signal estimate comprises performing data recovery on the received OFDM signal after equalization with the coarse zero forcing function and removal of the distributed pilot signal.

5. The method of claim 1 , wherein removing the coarse data signal estimate from the received OFDM signal comprises:

applying the coarse channel estimate to the coarse data signal estimate in the frequency domain to generate a coarse frequency domain representation of a received data signal;

converting the coarse frequency domain representation of the received data signal to a coarse time domain representation of the received data signal; and

subtracting the coarse time domain representation of the received data signal from the received OFDM signal in the time domain to generate the residual pilot signal.

6. The method of claim 1 , wherein finely equalizing the received OFDM signal based on the fine channel estimate comprises:

converting the received OFDM signal to a frequency domain signal;

constructing a fine zero forcing function from the fine channel estimate; and

applying the fine zero forcing function to the frequency domain signal.

7. The method of claim 6 , wherein removing the distributed pilot signal from the OFDM signal finely equalized based on the fine channel estimate comprises removing the distributed pilot signal from the frequency domain signal after equalizing the received OFDM signal with the fine zero forcing function.

8. An apparatus comprising:

a coarse correlator configured to correlate a received orthogonal frequency division multiplexed (OFDM) signal against a pilot reference to obtain a coarse channel estimate, the received OFDM signal comprising a distributed pilot signal and an OFDM data signal;

a coarse equalizer configured to equalize the received OFDM signal based on the coarse channel estimate;

a coarse pilot removal module configured to remove the distributed pilot signal from the received OFDM signal after coarse equalization;

a data recovery module configured to perform data recovery on the received OFDM signal after coarse removal of the distributed pilot signal to produce a coarse data signal estimate;

a data signal removal module configured to remove the coarse data signal estimate from the received OFDM signal using the coarse channel estimate to generate a residual pilot signal;

a fine correlator configured to correlate the residual pilot signal against the pilot reference to obtain a fine channel estimate;

a fine equalizer configured to equalize the received OFDM signal based on the fine channel estimate; and

a fine pilot removal module configured to remove the distributed pilot signal from the received OFDM signal after fine equalization to generate a fine data signal estimate from which data is recoverable.

9. The apparatus of claim 8 , wherein the coarse equalizer is further configured to: convert the received OFDM signal to a frequency domain signal;

construct a coarse zero forcing function from the coarse channel estimate; and

apply the coarse zero forcing function to the frequency domain signal to equalize the received OFDM signal.

10. The apparatus of claim 9 , wherein the coarse pilot removal module is further configured to remove the distributed pilot signal from the frequency domain signal after coarse equalization of the received OFDM.

11. The apparatus of claim 8 , wherein the data signal removal module is further configured to:

apply the coarse channel estimate to the coarse data signal estimate in the frequency domain to generate a coarse frequency domain representation of a received data signal;

convert the coarse frequency domain representation of the received data signal to a coarse time domain representation of the received data signal; and

subtract the coarse time domain representation of the received data signal from the received OFDM signal in the time domain to generate the residual pilot signal.

12. The apparatus of claim 8 , wherein the fine equalizer is further configured to:

convert the received OFDM signal to a frequency domain signal;

construct a fine zero forcing function from the fine channel estimate; and

apply the fine zero forcing function to the frequency domain signal to equalize the received OFDM signal.

13. The apparatus of claim 12 , wherein the fine pilot removal module is further configured to remove the distributed pilot signal from the frequency domain signal after fine equalization of the received OFDM signal.

14. A non-transitory computer readable medium encoded with software comprising processor-executable instructions that, when executed by a processor, cause the processor to perform functions of:

coarsely correlating a received orthogonal frequency division multiplexed (OFDM) signal against a pilot reference to obtain a coarse channel estimate, the received OFDM signal comprising a distributed pilot signal and an OFDM data signal;

coarsely equalizing the received OFDM signal based on the coarse channel estimate;

removing the distributed pilot signal from the received OFDM signal after coarsely equalizing to generate a coarse data signal estimate;

removing the coarse data signal estimate from the received OFDM signal using the coarse channel estimate to generate a residual pilot signal;

finely correlating the residual pilot signal against the pilot reference to obtain a fine channel estimate;

finely equalizing the received OFDM signal based on the fine channel estimate; and

removing the distributed pilot signal from the received OFDM signal after fine equalization to generate a fine data signal estimate from which data is recoverable.

15. The non-transitory computer readable medium of claim 14 , wherein the instructions that cause the processor to coarsely equalize include instructions that cause the processor to perform the further functions of:

converting the received OFDM signal to a frequency domain signal;

constructing a coarse zero forcing function from the coarse channel estimate; and

applying the coarse zero forcing function to the frequency domain signal.

16. The non-transitory computer readable medium of claim 15 , wherein the instructions that cause the processor to remove the distributed pilot signal from the OFDM signal coarsely equalized include instructions that cause the processor to remove the distributed pilot signal from the frequency domain signal after equalizing the received OFDM signal with the coarse zero forcing function.

17. The non-transitory computer readable medium of claim 15 , wherein the instructions that cause the processor to generate the coarse data signal estimate include instructions that cause the processor to perform data recovery on the received OFDM signal after equalization with the coarse zero forcing function and to remove of the distributed pilot signal.

18. The non-transitory computer readable medium of claim 14 , wherein the instructions that cause the processor to remove the coarse data signal estimate from the received OFDM signal include instructions that cause the processor to perform the further functions of:

applying the coarse channel estimate to the coarse data signal estimate in the frequency domain to generate a coarse frequency domain representation of a received data signal;

converting the coarse frequency domain representation of the received data signal to a coarse time domain representation of the received data signal; and

subtracting the coarse time domain representation of the received data signal from the received OFDM signal in the time domain to generate the residual pilot signal.

19. The non-transitory computer readable medium of claim 14 , wherein the instructions that cause the processor to finely equalize the received OFDM signal include instructions that cause the processor to perform the further functions of:

converting the received OFDM signal to a frequency domain signal;

constructing a fine zero forcing function from the fine channel estimate; and

applying the fine zero forcing function to the frequency domain signal.

20. The non-transitory computer readable medium of claim 19 , wherein the instructions that cause the processor to remove the distributed pilot signal from the OFDM signal finely equalized based on the fine channel estimate include instructions that cause the processor to remove the distributed pilot signal from the frequency domain signal after equalizing the received OFDM signal with the fine zero forcing function.