Patent ID: 7003100

Claim:
A modem having a transmit path carrying a transmit signal, a receive path carrying a receive signal, and an echo canceler, the transmit path including an inverse fast Fourier transform (IFFT) circuit for converting the transmit signal from the frequency domain to the time domain and the receive path including a fast Fourier transform (FFT) circuit for converting the receive signal from the time domain to the frequency domain, said echo canceler comprising: a cyclic echo synthesizer sub-canceler (CESS) having an input for receiving the transmit signal in the time domain and further having an output for producing a cyclic echo signal; a first algebraic combining unit for adding said cyclic echo signal to the receive signal in the time domain; a frame alignor having an input for coupling to the output of said first algebraic combining unit, said frame alignor producing a frame alignment signal, wherein said CESS further has an adaptive input for receiving said frame alignment signal; a switch coupled between the input of said frame alignor and the output of said first algebraic combining unit, said switch coupling the input of said frame alignor to the output of said first algebraic combining unit during a training period for frame synchronization of said cyclic echo synthesizer sub-canceler; an echo canceler having an input for receiving the transmit signal in the frequency domain, an adaptive input for receiving an adaptive signal, and an output for producing an echo cancellation signal based on the transmit signal and said adaptive signal; a second algebraic combining unit for subtracting said echo cancellation signal from the receive signal in the frequency domain to produce a resultant signal at an output; and a frequency domain equalizer having an input coupled to the output of said second algebraic combining unit for receiving the resultant signal, said frequency domain equalizer producing said adaptive signal.