Signal processing apparatus and method

1. A signal processing apparatus, comprising:

computation means for performing transform computation adapted to Fourier-transform a time domain Orthogonal Frequency Division Multiplexing (OFDM) signal into a frequency domain OFDM signal;

processing means for performing carrier frequency offset detection adapted to detect an estimated carrier frequency offset that is an error of a carrier used for demodulation of the OFDM signal; and

carrier frequency offset correction means for performing carrier frequency offset correction to correct the carrier frequency offset of the frequency domain OFDM signal in accordance with the estimated carrier frequency offset, wherein

the OFDM signal contains a first preamble signal and a second preamble signal following the first preamble signal, and

the computation means performs the transform computation of the second preamble signal in parallel with the carrier frequency offset detection performed by the processing means using the first preamble signal.

2. The signal processing apparatus of claim 1 , wherein

the processing means finds a sum of subcarriers at positions having, as a starting point, a position deviating by an offset amount from the beginning of the first preamble signal for each of a plurality of offset amounts in a detection range spanning from minimum to maximum of the offset amount, the offset amount representing a carrier frequency offset of a predetermined number of subcarriers,

the processing means detects the maximum of all the sums of the subcarriers obtained for each of the plurality of offset amounts so as to detect the offset amount associated with the maximum sum as the estimated carrier frequency offset,

the processing means stores the estimated carrier frequency offset in association with a channel of the OFDM signal in which the estimated offset is detected,

the processing means sets a default range as a detection range for use in the carrier frequency offset detection when the OFDM signal of a channel, for which the estimated carrier frequency offset is not stored, is received, and

the processing means sets, as the detection range, a range narrower than the default range that includes the estimated carrier frequency offset associated with the channel when the OFDM signal of a channel, for which the estimated carrier frequency offset is stored, is received.

3. The signal processing apparatus of claim 1 , further comprising:

other carrier frequency offset correction means for performing carrier frequency offset correction to correct the carrier frequency offset of the time domain OFDM signal in accordance with the estimated carrier frequency offset, wherein

the OFDM signal is transmitted in units of a frame, with each frame containing the one first preamble signal and the one or more second preamble signals, and

the first frame after the beginning of reception of the OFDM signal is subjected to the carrier frequency offset correction by the carrier frequency offset correction means, and the succeeding frames are subjected to the carrier frequency offset correction by the other carrier frequency offset correction means.

4. A signal processing method, comprising the steps of:

performing transform computation to Fourier-transform a time domain Orthogonal Frequency Division Multiplexing (OFDM) signal into a frequency domain OFDM signal;

performing carrier frequency offset detection to detect an estimated carrier frequency offset that is an error of a carrier used for demodulation of the OFDM signal; and

performing carrier frequency offset correction to correct the carrier frequency offset of the frequency domain OFDM signal in accordance with the estimated carrier frequency offset, wherein

the OFDM signal contains a first preamble signal and a second preamble signal following the first preamble signal, and

the transform computation of the second preamble signal is performed in parallel with the carrier frequency offset detection using the first preamble signal.

5. A signal processing apparatus, comprising:

a computation device to perform transform computation to Fourier-transform a time domain Orthogonal Frequency Division Multiplexing (OFDM) signal into a frequency domain OFDM signal;

a processing device to perform carrier frequency offset detection to detect an estimated carrier frequency offset that is an error of a carrier used for demodulation of the OFDM signal; and

a carrier frequency offset correction device to perform carrier frequency offset correction to correct the carrier frequency offset of the frequency domain OFDM signal in accordance with the estimated carrier frequency offset, wherein

the OFDM signal contains a first preamble signal and a second preamble signal following the first preamble signal, and

the computation device performs the transform computation of the second preamble signal in parallel with the carrier frequency offset detection performed by the processing device using the first preamble signal.