Granted Patent B2

US 7,489,734 · App. 11/320,568 · Granted Feb 10, 2009

Abstract

Claims (64)

1. An equalization method in a radio receiver, the method comprising:

receiving a plurality of information symbols;

determining a radio channel impulse response from the received information symbols;

calculating filter coefficients for an equalization filter with a zero forcing algorithm based on the radio channel impulse response;

calculating a frequency domain representation of the radio channel impulse response;

modifying a frequency spectrum of at least one portion of the received plurality of information symbols with the frequency domain representation of the radio channel impulse response; and

filtering the information symbols having the modified frequency spectrum with the equalization filter having the calculated filter coefficients.

2. The method of claim 1 , wherein the plurality of information symbols comprises a plurality of data symbols and a plurality of training sequence symbols.

3. The method of claim 2 , further comprising:

determining the radio channel impulse response from the training sequence symbols.

4. The method of claim 1 , wherein the modifying of the frequency spectrum of the at least one portion of the received plurality of information symbols comprises attenuating the frequencies in which a power level of the information symbols is degraded due to frequency selectivity of a radio channel.

5. The method of claim 1 , wherein the modifying of the frequency spectrum of the at least one portion of the received plurality of information symbols comprises:

transforming the at least one portion of the received plurality of information symbols into a frequency domain;

weighting the transformed at least one portion of the received plurality of information symbols with the calculated frequency domain representation of the radio channel impulse response, and

inverse transforming the weighted at least one portion of the received plurality of information symbols back into a time domain.

6. The method of claim 5 , wherein the transforming of the at least one portion of the received plurality of information symbols into the frequency domain comprises

calculating a fast Fourier transform (FFT) of the at least one portion of the received plurality of information symbols, and

the inverse transforming of the weighted at least one portion of the received plurality of information symbols into the time domain comprises

calculating an inverse fast Fourier transform (IFFT) of the weighted at least one portion of the received plurality of information symbols.

7. The method of claim 1 , wherein the calculating of the frequency domain representation of the radio channel impulse response comprises:

transforming the radio channel impulse response into the frequency domain to obtain a transformed radio channel frequency response;

calculating an absolute value of the transformed radio channel frequency response to obtain an amplitude spectrum of the radio channel; and

modifying the amplitude spectrum of the radio channel with an adjustment parameter.

8. The method of claim 7 , wherein modifying the amplitude spectrum comprises raising the amplitude spectrum to an exponent defined by the adjustment parameter.

9. The method of claim 1 , wherein the filtering comprises

calculating a convolution between the plurality of information symbols and the filter coefficients determined for the zero forcing algorithm.

10. The method of claim 1 , wherein the filtering comprises

multiplying a frequency domain representation of the modified at least one portion of the information symbols and a frequency domain representation of the filter coefficients determined for the zero forcing algorithm, and the method further comprising:

inverse transforming the filtered at least one portion of the information symbols into a time domain.

11. A radio receiver, comprising:

a communication interface for receiving radio signals comprising a plurality of information symbols and

a processing unit configured to determine a radio channel impulse response from the received information symbols, calculate filter coefficients for an equalization filter with a zero forcing algorithm based on the radio channel impulse response, calculate a frequency domain representation of the radio channel impulse response, modify a frequency spectrum of at least one portion of the received plurality of information symbols with the frequency domain representation of the radio channel impulse response, and filter the information symbols having the modified frequency spectrum with the equalization filter having the calculated filter coefficients.

12. The radio receiver of claim 11 , wherein the plurality of information symbols comprises a plurality of data symbols and a plurality of training sequence symbols.

13. The radio receiver of claim 12 , wherein the processing unit is further configured to determine the radio channel impulse response from the training sequence symbols.

14. The radio receiver of claim 11 , wherein the processing unit is further configured to modify the frequency spectrum of the at least one portion of the received plurality of information symbols by attenuating the frequencies in which a power level of the information symbols is degraded due to frequency selectivity of a radio channel.

15. The radio receiver of claim 11 , wherein the processing unit is further configured to modify the frequency spectrum of the at least one portion of the received plurality of information symbols by transforming the at least one portion of the received plurality of information symbols into a frequency domain, weighting the transformed at least one portion of the received plurality of information symbols with the calculated frequency domain representation of the radio channel impulse response, and inverse transforming the weighted at least one portion of the received plurality of information symbols back into a time domain.

16. The radio receiver of claim 15 , wherein the processing unit is further configured to transform the at least one portion of the received plurality of information symbols into the frequency domain by calculating a fast Fourier transform (FFT) of the transformed at least one portion of the received plurality of information symbols and to carry out the inverse transform of the weighted at least one portion of the received plurality of information symbols by calculating an inverse fast Fourier transform (IFFT) of the weighted at least one portion of the received plurality of information symbols.

17. The radio receiver of claim 11 , wherein the processing unit is further configured to calculate the frequency domain representation of the radio channel impulse response by transforming the radio channel impulse response into a frequency domain to obtain a transformed radio channel frequency response, calculating an absolute value of the transformed radio channel frequency response to obtain an amplitude spectrum of the radio channel, and modifying the amplitude spectrum of the radio channel with an adjustment parameter.

18. The radio receiver of claim 17 , wherein the processing unit is further configured to modify the amplitude spectrum by raising the amplitude spectrum to an exponent defined by the adjustment parameter.

19. The radio receiver of claim 11 , wherein the processing unit is further configured to filter the information symbols by calculating a convolution between the plurality of information symbols and the filter coefficients determined for the zero forcing algorithm in a time domain.

20. The radio receiver of claim 11 , wherein the processing unit is further configured to filter the information symbols by multiplying a frequency domain representation of the modified at least one portion of the information symbols and a frequency domain representation of the filter coefficients determined for the zero forcing algorithm, and inverse transform the filtered at least one portion of the information symbols into a time domain.

21. A radio receiver, comprising:

communication means for receiving radio signals comprising a plurality of information symbols;

means for receiving the plurality of information symbols;

means for determining a radio channel impulse response from the received information symbols;

means for calculating filter coefficients for an equalization filter with a zero forcing algorithm based on the radio channel impulse response;

means for calculating a frequency domain representation of the radio channel impulse response;

means for modifying a frequency spectrum of at least a portion of the received plurality of information symbols with the frequency domain representation of the radio channel impulse response; and

means for filtering the information symbols having the modified frequency spectrum with the equalization filter having the calculated filter coefficients.

22. A computer program product embodied on a computer readable medium, the computer program product encoding a computer program of instructions for executing a computer process for equalization in a radio receiver, the process comprising:

receiving a plurality of information symbols;

determining a radio channel impulse response from the received information symbols;

calculating filter coefficients for an equalization filter with a zero forcing algorithm based on the radio channel impulse response;

calculating a frequency domain representation of the radio channel impulse response;

modifying a frequency spectrum of at least a portion of the received plurality of information symbols with the frequency domain representation of the radio channel impulse response; and

filtering the information symbols having the modified frequency spectrum with the equalization filter having the calculated filter coefficients.

23. A computer program distribution medium readable by a computer and encoding a computer program of instructions for executing a computer process for equalization in a radio receiver, the process comprising:

receiving a plurality of information symbols;

determining a radio channel impulse response from the received information symbols;

calculating filter coefficients for an equalization filter with a zero forcing algorithm based on the radio channel impulse response;

calculating a frequency domain representation of the radio channel impulse response;

modifying a frequency spectrum of at least a portion of the received plurality of information symbols with the frequency domain representation of the radio channel impulse response; and

filtering the information symbols having the modified frequency spectrum with the equalization filter having the calculated filter coefficients.

24. The computer program distribution medium of claim 23 , wherein the distribution medium including at least one of the following media: a computer readable medium, a program storage medium, a record medium, a computer readable memory, a computer readable software distribution package, a computer readable signal, a computer readable telecommunications signal, and a computer readable compressed software package.

Assignments (7)