An efficient algorithm is described for use with OFDM receivers that characterizes the impulse response of a communication channel using frequency domain techniques that reduce computational and memory requirements, relative to time-domain cross-correlation methods, without sacrificing algorithm performance. An FFT engine is used to transform a time domain input sequence, the transformed sequence is multiplied by the conjugate of the expected sequence, the product of several sequences is averaged, then the FFT engine transforms the average back to a time domain sequence, the magnitude of which is the impulse response of the channel.