Granted Patent B2

US 7,711,031 · App. 11/766,814 · Granted May 4, 2010

Abstract

Claims (51)

1. A method of adaptively performing inter-carrier-interference (ICI) canceling in an Orthogonal Frequency-Division Multiplexing (OFDM) system, said method comprising:

taking a Fast Fourier Transform (FFT) of a wireless electrical signal to produce an OFDM signal;

estimating a DC component of a frequency-selective channel in said OFDM system;

obtaining an initial estimate of data symbols associated with data bits of said OFDM signal;

correcting said data bits with a Viterbi decoder;

encoding the corrected data bits to acquire corrected data symbols;

re-estimating said DC component of said frequency-selective channel using said corrected data symbols;

filtering said corrected data symbols and sub-carrier of said frequency-selective channel;

calculating a first order differential function of said frequency-selective channel based on successive ones of said corrected data symbols;

removing an ICI component from the calculated first order differential function; and

re-estimating said data symbols as a function of the removed ICI component.

2. The method of claim 1 , wherein said filtering occurs using a low pass filter comprising a bank of filters.

3. The method of claim 2 , wherein said bank of filters comprise eight filters.

4. The method of claim 2 , further comprising mapping an estimated channel length to one of the filters in said bank of filters.

5. The method of claim 1 , further comprising repeating the estimating step through the removing step prior to performing the re-estimating of said data symbols as a function of the removed ICI component.

6. The method of claim 1 , further comprising using the re-estimated data symbols to process said OFDM signal for transmission in said OFDM system.

7. The method of claim 1 , wherein said first order differential function is based on an immediate preceding and an immediate succeeding data symbol of a current data symbol.

8. A program storage device readable by computer comprising a program of instructions executable by said computer to perform a method of adaptively performing inter-carrier-interference (ICI) canceling in an Orthogonal Frequency-Division Multiplexing (OFDM) system, said method comprising:

taking a Fast Fourier Transform (FFT) of a wireless electrical signal to produce an OFDM signal;

estimating a DC component of a frequency-selective channel in said OFDM system;

obtaining an initial estimate of data symbols associated with data bits of said OFDM signal;

correcting said data bits with a Viterbi decoder;

encoding the corrected data bits to acquire corrected data symbols;

re-estimating said DC component of said frequency-selective channel using said corrected data symbols;

filtering said corrected data symbols and sub-carrier of said frequency-selective channel;

calculating a first order differential function of said frequency-selective channel based on successive ones of said corrected data symbols;

removing an ICI component from the calculated first order differential function; and

re-estimating said data symbols as a function of the removed ICI component.

9. The program storage device of claim 8 , wherein said filtering occurs using a low pass filter comprising a bank of filters.

10. The program storage device of claim 9 , wherein said bank of filters comprise eight filters.

11. The program storage device of claim 9 , wherein said method further comprises mapping an estimated channel length to one of the filters in said bank of filters.

12. The program storage device of claim 8 , wherein said method further comprises repeating the estimating step through the removing step prior to performing the re-estimating of said data symbols as a function of the removed ICI component.

13. The program storage device of claim 8 , wherein said method further comprises using the re-estimated data symbols to process said OFDM signal for transmission in said OFDM system.

14. The program storage device of claim 8 , wherein said first order differential function is based on an immediate preceding and an immediate succeeding data symbol of a current data symbol.

15. A system for adaptively performing inter-carrier-interference (ICI) canceling comprising:

a processor adapted to:

take a Fast Fourier Transform (FFT) of a wireless electrical signal to produce an Orthogonal Frequency-Division Multiplexing (OFDM) signal;

estimate a DC component of a frequency-selective channel in said OFDM system; and

obtain an initial estimate of data symbols associated with data bits of said OFDM signal;

a Viterbi decoder adapted to correct said data bits;

an encoder adapted to re-encode the corrected data bits to acquire corrected data symbols;

processing means for re-estimating said DC component of said frequency-selective channel using said corrected data symbols;

a filter adapted to filter said corrected data symbols and sub-carrier of said frequency-selective channel;

processing means for calculating a first order differential function of said frequency-selective channel based on successive ones of said corrected data symbols;

processing means for removing an ICI component from the calculated first order differential function; and

processing means for re-estimating said data symbols as a function of the removed ICI component.

16. The system of claim 15 , wherein said filter comprises a low pass filter comprising a bank of filters.

17. The system of claim 16 , wherein said bank of filters comprise eight filters.

18. The system of claim 16 , further comprising processing means for mapping an estimated channel length to one of the filters in said bank of filters.

19. The system of claim 15 , further comprising processing means for using the re-estimated data symbols to process said OFDM signal for transmission in said OFDM system.

20. The system of claim 15 , wherein said first order differential function is based on an immediate preceding and an immediate succeeding data symbol of a current data symbol.

Assignments (31)