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

A method of training tap coefficients of an adaptive equalizer having a first number of taps, for equalizing duration of an impulse response of 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 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 producing a windowed target impulse response 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 and transforming the selected consecutive tap values into the frequency-domain;
• a tap-coefficient update step of producing an updated tap coefficient vector by updating a frequency-domain tap coefficient vector making use of a frequency-domain LMS 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 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, normalizing the selected cosecutive coefficients and shifting the normalized consecutive coefficients to be assigned from a top of the windowed tap coefficients.

A method of training tap coefficients of an adaptive equalizer having a first number of taps, for equalizing duration of an impulse response of a transmission channel to be shorter than a second number of taps with a sufficiently small error, having a step of initializing a target impulse response and 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 into a time-domain;
• a target-impulse-response update step of producing an updated target impulse response by updating the windowed target impulse response multiplied by a normalization coefficient making use of a frequency-domain LMS method with an error value defined as a difference of a product of the normalization coefficient, a training vector and the windowed target impulse response to a product of a frequency-domain tap coefficient vector and a reception signal vector, the training vector being produced by encoding a frequency-domain vector with a replica of the PRBS, the frequency-domain tap coefficient vector being obtained by transforming the windowed tap coefficients into a frequency-domain, and the reception signal vector being obtained by transforming the transmission signal received through the transmission channel into the frequency-domain;
• a target-impulse-response windowing step of producing a windowed target impulse response 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 and transforming the selected consecutive tap values into the frequency-domain;
• a tap-coefficient update step of producing an updated tap coefficient vector by dividing a product of the windowed target response and the reception signal vector with the training vector;
• and
• a tap-coefficient windowing step of outputting the windowed tap coefficients together with the normalization coefficient, the windowed tap coefficients being produced 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, normalizing the selected consecutive coefficients and shifting the normalized consecutive coefficients to be assigned from a top of the windowed tap coefficients, and the normalization coefficient being obtained by dividing the normalized consecutive coefficients with the selected consecutive coefficients before normalization.

A training circuit for training tap coefficients of an adaptive equalize having a first number of taps to be used for equalizing duration of an impulse response of a transmission channel to be shorter than a second number of taps with a sufficiently small error;

• the training circuit comprising:
• a transmitter for transmitting a transmission signal which is produced by transforming a frequency-domain transmission vector encoded with a PRBS into a time-domain;
• a target impulse response update means for 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 means for 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 means for 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 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;
• a tap-coefficient windowing means for 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;
• and
• a control means for initializing the windowed tap coefficients to some predetermined values, controlling the transmitter, the target-impulse-response update means, the target-impulse-response windowing means, the tap-coefficient update means and the tap-coefficient windowing means to update the windowed target impulse response and the windowed tap coefficients alternately and recursively by generating the PRBS and the replica of the PRBS repeatedly until a certain convergence condition of the windowed tap coefficients is attained, and outputting the windowed tap coefficients as the tap coefficients of the adaptive equalizer after the certain convergence condition is attained.

A training circuit for training tap coefficients of an adaptive equalizer having a first number of taps to be used for equalizing duration of an impulse response of a transmission channel to be shorter than a second number of taps with a sufficiently small error;

• the training circuit comprising:
• a transmitter for transmitting a transmission signal which is produced by transforming a frequency-domain transmission vector encoded with a PRBS into a time-domain;
• a target-impulse-response update means for 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 the 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 means for producing a windowed target impulse response 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 and transforming the selected consecutive tap values into the frequency-domain;
• a tap-coefficient update means for producing an updated tap coefficient vector by updating a frequency-domain tap coefficient vector by making use of a frequency-domain LMS 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 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;
• a tap-coefficient windowing means for 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, normalizing the selected cosecutive coefficients and shifting the normalized consecutive coefficients to be assigned from a top of the windowed tap coefficients and;
• a control means for initializing the windowed tap coefficients to some predetermined values, controlling the transmitter, the target-impulse-response update means, the target-impulse-response windowing means, the tap-coefficient update means and the tap-coefficient windowing means to update the windowed target impulse response and the windowed tap coefficients alternately and recursively by generating the PRBS and the replica of the PRBS repeatedly until a certain convergence condition of the windowed tap coefficient is attained, and outputting the windowed tap coefficients as the tap coefficients of the adaptive equalizer after the certain convergence condition is attained.

A training circuit for training tap coefficients of an adaptive equalizer having a first number of taps to be used for equalizing duration of an impulse response of a transmission channel to be shorter than a second number of taps with a sufficiently small error;

• the training circuit comprising:
• a transmitter for transmitting a transmission signal which is produced by transforming a frequency-domain transmission vector encoded with a PRBS into a time-domain;
• a target-impulse-response update means for producing an updated target impulse response by updating the windowed target impulse response multiplied by a normalization coefficient making use of a frequency-domain LMS method with an error value defined as a difference of a product of the normalization coefficient, a training vector and the windowed target impulse response to a product of a frequency-domain tap coefficient vector and a reception signal vector, the training vector being produced by encoding a frequency-domain vector with a replica of the PRBS, the frequency-domain tap coefficient vector being obtained by transforming the windowed tap coefficients into a frequency-domain, and the reception signal vector being obtained by transforming the transmission signal received through the transmission channel into the frequency-domain;
• a target-impulse-response windowing means for producing a windowed target impulse response 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 and transforming the selected consecutive tap values into the frequency-domain;
• a tap-coefficient update means for producing an updated tap coefficient vector by dividing a product of the windowed target response and the reception signal vector with the training vector;
• a tap-coefficient windowing means for outputting the windowed tap coefficients together with the normalization coefficient, the windowed tap coefficients being produced 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, normalizing the selected consecutive coefficients and shifting the normalized consecutive coefficients to be assigned from a top of the windowed tap coefficients, and the normalization coefficient being obtained by dividing the normalized consecutive coefficients with the selected consecutive coefficients before normalization;
• and
• a control means for initializing the windowed target impulse response and the windowed tap coefficients to some predetermined values, controlling the transmitter, the target-impulse-response update means, the target-impulse-response windowing means, the tap-coefficient update means and the tap-coefficient windowing means to update the windowed target impulse response and the windowed tap coefficients alternately and recursively by generating the PRBS and the replica of the PRBS repeatedly until a certain convergence condition of the windowed tap coefficients is attained, and outputting the windowed tap coefficients as the tap coefficients of the adaptive equalizer after the certain convergence condition is attained.