The embodiments disclose a method in a base station for extracting a resource block at a frequency band from a signal received from a terminal device in a radio communication system employing OFDM. The method comprising: removing a CP portion corresponding to the resource block from the signal; for each of a predetermined number of successive symbols in the signal after the CP portion corresponding to the resource block has been removed, performing a FFT of the symbol, extracting a frequency domain signal corresponding to the frequency band from the FFT of the symbol, performing an IFFT on the extracted frequency domain signal to yield a time domain signal, and storing the time domain signal to form a time sequence by concatenation; performing a FFT of the stored time sequence; and extracting subcarriers corresponding to the resource block from the FFT of the stored time sequence.