a method of calculating echo - canceling coefficients to be used by an echo cancellation filter in a communication modem , the communication modem having a fast fourier transform serial to parallel interface , the method including the steps of transmitting a first signal including a wide - band cyclic sequence , generating an echo signal based on the first signal and a plurality of ec coefficients , receiving a second signal including a wide - band cyclic sequence , subtracting the echo - canceled signal from the second signal to produce an echo - cancelled signal , transforming the echo - cancelled signal via the fft serial to parallel interface to produce a transformed echo - cancelled signal , and calculating the plurality of ec coefficients based on the transformed echo - cancelled signal .