Adaptive known signal canceller

A receiver responsive to at least one input signal and operative to generate an equalized signal comprising:

• an adaptive known signal canceller responsive to an input signal of a communication channel including frames of information, said input signal representing a transmitted signal that has been distorted by the communication channel, said adaptive known signal canceller operative to generate a time domain unknown signal, and further operative to generate an estimated channel impulse response signal representing substantially the impulse response of the channel, the adaptive known signal canceller including a known signal canceller filter configured to generate a filtered known signal, the known signal canceller filter configured to receive a coefficient update signal that is used to update the coefficients, the adaptive known signal canceller further including a subtractor responsive to the input signal and operative to generate an output signal, the subtractor configured to subtract the filtered known signal from the input signal, the adaptive known signal canceller further including a known signal canceller update unit responsive to a desired signal, the desired signal representing the desired output signal with the known signal part having been removed, the known signal canceller update unit operative to provide the coefficient update signal to the known signal canceller filter based on the difference between the output signal and the desired signal, so that the coefficients correspond to an estimate of the impulse response of the channel, and a known portion of the transmitted signal is adaptively removed from the input signal;
• an equalizer coefficient computation block responsive to the estimated channel impulse response and operative to compute and generate time domain equalizer coefficients;
• and
• a time domain equalizer responsive to the time domain equalizer coefficients and to the output signal, and operative to generate an equalized signal, the time domain equalizer configured to filter the output signal using the time domain equalizer coefficients to yield an equalized signal.

An adaptive known signal canceller adaptive for use in a receiver configured to receive at least one channel carrying information, said adaptive known canceller comprising:

• a known signal canceller filter responsive to a known signal including a known portion of a transmitted signal, the known signal canceller filter operative to generate a filtered known signal;
• a subtractor unit responsive to an input signal and operative to generate an output signal, the subtractor unit configured to subtract the filtered known signal from the input signal to generate an output signal, such that the known portion of the transmitted signal is substantially removed from the input signal;
• and
• a known signal canceller update unit, responsive to a desired signal and an output signal and operative to adjust the coefficients of the known signal canceller filter based on the difference between the output signal and the desired signal, so that the filter coefficients substantially reflect the impulse response of a channel.

An adaptive known signal canceller operative to perform channel estimation and to provide an output signal in response to an input signal, comprising:

• a known signal generator, operative to generate a known signal consisting of a known portion of a transmitted signal;
• a known signal canceller filter, responsive to the known signal and operative to generate a filtered known signal;
• a signal subtractor, responsive to an input signal and the filtered known signal, and operative to compute the difference between the input signal and the filtered known signal to generate an output signal;
• and
• a known signal canceller update unit, responsive to a desired signal and an output signal, and operative to continually adjust the coefficients of the known signal canceller filter based on the difference between the output signal and a desired signal, to generate an estimated channel impulse response.

An adaptive known signal canceller operative to provide an output signal in response to a input signal, comprising:

• a known signal generator, operative to generate a known signal consisting of a known portion of a transmitted signal;
• a known signal canceller filter, responsive to the known signal and operative to generate a filtered known signal;
• a carrier rotation block, responsive to an input signal and operative to generate a rotated signal, wherein said rotated signal represents the input signal with a carrier phase rotation;
• a signal subtractor, responsive to the rotated signal and the filtered known signal, and operative to compute the difference between the rotated signal and the filtered known signal to generate an output signal;
• a known signal canceller update unit, responsive to a desired signal and an output signal, and operative to adjust the coefficients of the known signal canceller filter based on the difference between the output signal and a desired signal, to generate an estimated channel impulse response;
• and
• a phase error detection block, responsive to the rotated signal and the filtered known signal, and operative to generate a phase error signal;
• wherein the carrier rotation block is further operative to use said phase error signal to update the phase rotation for a subsequent value of the input signal.

An adaptive known signal canceller comprising:

• means for generating a known signal consisting of a known portion of a transmitted signal;
• means for receiving the known signal;
• means for generating a filtered known signal;
• means for receiving an input signal and the filtered known signal;
• means for computing the difference between the input signal and the filtered signal to generate an output signal means for receiving a desired signal and an output signal;
• means for adjusting the coefficients of the known signal canceller filter based on the difference between the output signal and a desired signal, to generate an estimated channel impulse response.

A method of channel impulse response estimation comprising:

• a. receiving an input signal sample;
• b. determining if said sample corresponds to a known portion of the signal, and if it does, generating a sample of the known portion of the signal;
• c. generating a filtered known sample using one or more samples of the known portion of the signal;
• d. generating an output sample by subtracting the sample of the filtered known signal from the sample of the input signal;
• e. updating the filter coefficients of the known signal canceller filter block based on the difference between the output signal and a desired signal;
• and
• f. repeating steps a.-e. so long as the input signal is received.

A non-transitory computer-readable medium containing a description expressed in a hardware description language which is interpreted by a computer to specify a circuit that performs a method to generate an equalized signal comprising:

• an adaptive known signal canceller responsive to an input signal of a communication channel including frames of infoiiiiation, said input signal including orthogonal sub-carriers and representing a transmitted signal that has been distorted by the communication channel, said adaptive known signal canceller operative to generate a time domain unknown signal, and further operative to generate an estimated channel impulse response signal representing substantially the impulse response of the channel, the adaptive known signal canceller including a known signal canceller filter configured to generate a filtered known signal, the known signal canceller filter configured to receive a coefficient update signal that is used to update the coefficient, the adaptive known signal canceller further including a subtractor responsive to the input signal and operative to generate an output signal, the subtractor configured to subtract the filtered known signal from the input signal, the adaptive known signal canceller further including a known signal canceller update unit responsive to a desired signal, the desired signal representing the desired output signal with the known signal part having been removed, the known signal canceller update unit operative to provide the coefficient update signal to the known signal canceller filter based on the difference between the output signal and the desired signal, so that the coefficients correspond to an estimate of the impulse response of the channel, and a known portion of the transmitted signal is adaptively removed from the input signal;
• and
• a frequency domain equalizer responsive to a frequency representation of the estimated channel impulse response and a frequency representation of a cyclically restored time domain unknown signal and operative to generate an frequency domain equalized signal, the frequency domain equalizer configured to remove the effects of the channel thereby generating a frequency domain estimate of the unknown part of the transmitted signal.

A non-transitory computer-readable medium containing a description expressed in a hardware description language which is interpreted by a computer to specify a circuit that performs a method of channel impulse response estimation comprising:

• an adaptive known signal canceller responsive to an input signal of a communication channel including frames of information, said input signal representing a transmitted signal that has been distorted by the communication channel, said adaptive known signal canceller operative to generate a time domain unknown signal, and further operative to generate an estimated channel impulse response signal representing substantially the impulse response of the channel, the adaptive known signal canceller including a known signal canceller filter configured to generate a filtered known signal, the known signal canceller filter configured to receive a coefficient update signal that is used to update the coefficients, the adaptive known signal canceller further including a subtractor responsive to the input signal and operative to generate an output signal, the subtractor configured to subtract the filtered known signal from the input signal, the adaptive known signal canceller further including a known signal canceller update unit responsive to a desired signal, the desired signal representing the desired output signal with the known signal part having been removed, the known signal canceller update unit operative to provide the coefficient update signal to the known signal canceller filter based on the difference between the output signal and the desired signal, so that the coefficients correspond to an estimate of the impulse response of the channel, and a known portion of the transmitted signal is adaptively removed from the input signal;
• a equalizer coefficient computation block responsive to the estimated channel impulse response and operative to compute and generate time domain equalizer coefficients;
• and
• a time domain equalizer responsive to the time domain equalizer coefficients and to the output signal, and operative to generate an equalized signal, the time domain equalizer configured to filter the output signal using the time domain equalizer coefficients to yield an equalized signal.

A non-transitory computer-readable medium containing a description expressed in a hardware description language which is interpreted by a computer to specify a circuit that performs a method to receive at least one channel carrying information, said circuit comprising:

• a known signal canceller filter responsive to a known signal including a known portion of a transmitted signal, the known signal canceller filter operative to generate a filtered known signal;
• a subtractor unit responsive to an input signal and operative to generate an output signal, the subtractor unit configured to subtract the filtered known signal from the input signal to generate an output signal, such that the known portion of the transmitted signal is substantially removed from the input signal;
• and
• a known signal canceller update unit, responsive to a desired signal and an output signal and operative to adjust the coefficients of the known signal canceller filter based on the difference between the output signal and the desired signal, so that the filter coefficients substantially reflect the impulse response of a channel.