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Method of and an apparatus for training tap coefficients of an adaptive equalizer

  • US 6,259,729 B1
  • Filed: 12/18/1998
  • Issued: 07/10/2001
  • Est. Priority Date: 12/19/1997
  • Status: Expired due to Fees
First Claim
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1. A method of training tap coefficients of an adaptive equalizer having a first number of taps, for equalizing duration of an impulse response for a transmission channel to be shorter than a second number of taps with a sufficiently small error, having a step of initializing windowed tap coefficients to some predetermined values, a step of repeating a training procedure until a certain convergence condition of the windowed tap coefficients is attained, and a step of outputting the windowed tap coefficients as the tap coefficients of the adaptive equalizer after the certain convergence condition is attained;

  • said training procedure comprising;

    a transmission step of transmitting a transmission signal which is produced by transforming a frequency-domain transmission vector encoded with a PRBS (Pseudo-Random Binary Sequence) into a time-domain;

    a target-impulse-response update step of producing an updated target impulse response by dividing an equalized reception signal vector with a training vector, the equalized reception signal vector being produced by transforming an equalized reception signal, which is obtained by processing the transmission signal received through the transmission channel with an equalizer having the first number of taps whereof coefficients are set to have values of the windowed tap coefficients, into a frequency-domain, and the training vector being produced by encoding a frequency-domain vector with a replica of the PRBS;

    a target-impulse-response windowing step of outputting a windowed target impulse response together with a normalization coefficient, the windowed target impulse response being produced by transforming the updated target impulse response into a time-domain updated target impulse response signal, selecting the second number of consecutive tap values giving a maximum total power from tap values of the time-domain updated target impulse response, normalizing the selected consecutive tap values and transforming the normalized consecutive tap values into the frequency-domain, and the normalization coefficient being obtained by dividing the normalized consecutive tap values with the selected consecutive tap values before normalization;

    a tap-coefficient update step of producing an updated tap coefficient vector by updating a frequency-domain tap coefficient vector multiplied by the normalization coefficient making use of a frequency-domain LMS (Least Mean Square) method with an error value defined as a difference of a product of the training vector and the windowed target impulse response to a product of the normalization coefficient, the frequency-domain tap coefficient vector and a reception signal vector, the frequency-domain tap coefficient vector being obtained by transforming the windowed tap coefficients into the frequency-domain, and the reception signal vector being obtained by transforming the transmission signal received through the transmission channel into the frequency-domain; and

    a tap-coefficient windowing step of producing the windowed tap coefficients by transforming the updated tap coefficient vector into updated tap coefficients, selecting the first number of consecutive coefficients giving a maximum total power from coefficients of the updated tap coefficients and shifting the selected consecutive coefficients to be assigned from a top of the windowed tap coefficients.

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