Patent ID: 7555047

Claim:
A method of detecting an echo signal in a frequency domain, comprising: interpolating at least one fast Fourier transformed Orthogonal Frequency Division Multiplexing (OFDM) received signal, in the time-domain; interpolating at least one signal generated by the time-domain interpolation in the frequency-domain, using a time-domain variable bandwidth Low-Pass Filter (LPF), with a bandwidth that varies in response to a bandwidth control signal; measuring at least one signal power ratio between a scattered pilot signal of the at least one signal generated by the time-domain interpolation and another scattered pilot signal of at least one signal generated by the frequency-domain interpolation; comparing the measured at least one signal power ratio to a threshold value to determine a state of an echo signal and generating the bandwidth control signal with the echo state information; and adaptively changing the bandwidth of the variable bandwidth LPF using the bandwidth control signal; and compensating for channel distortion in the fast Fourier transformed OFDM received signal using the signal generated by the frequency-domain interpolation.