Demodulating circuit, demodulating method, program, and receiving device

1. A demodulating circuit comprising:

Fast Fourier Transform (FFT) processing means for performing an FFT process on an Orthogonal Frequency Division Multiplexing (OFDM time-domain signal;

intercarrier interferential component removing means for removing an intercarrier interferential component from an OFDM frequency-domain signal which is produced when the FFT process is performed on the OFDM time-domain signal by said FFT processing means;

extracting means for extracting pilot signals representative of transmission path characteristics of a transmission path from said OFDM frequency-domain signal from which the intercarrier interferential component is removed by said intercarrier interferential component removing means;

transmission path characteristics estimating means for estimating transmission path characteristics represented by subsequently received pilot signals, based on the transmission path characteristics represented by said pilot signals extracted by said extracting means;

interpolating means for interpolating transmission path characteristics in a frequency direction based on the transmission path characteristics estimated by said transmission path characteristics estimating means thereby to estimate transmission path characteristics for all subcarriers;

symbol sequence estimating means for estimating a symbol sequence represented by said OFDM frequency-domain signal which is produced when the FFT process is performed on the OFDM time-domain signal by said FFT processing means, based on the transmission path characteristics for all subcarriers which are estimated by said interpolating means; and

interference replica generating means for generating an interference replica representing said intercarrier interferential component to be removed from said OFDM frequency-domain signal by said intercarrier interferential component removing means, based on the symbol sequence estimated by said symbol sequence estimating means and the transmission path characteristics for all subcarriers which are estimated by said interpolating means.

2. The demodulating circuit according to claim 1 , further comprising:

multiplying means for multiplying the OFDM time-domain signal on which the FFT process is to be performed by said FFT processing means by a window function;

processing means for determining an impulse response of said transmission path using all or part of the transmission path characteristics estimated for all the subcarriers after the FFT process; and

window function determining means for moving said window function to be used by said multiplying means in at least either one of a phase direction and a DC direction depending on a delay spread which is estimated from the impulse response of the transmission path which is determined by said processing means.

3. The demodulating circuit according to claim 1 , further comprising:

decimating means for decimating ones of said pilot signals extracted by said extracting means;

wherein said transmission path characteristics estimating means estimates the transmission path characteristics represented by the subsequently received pilot signals, based on transmission path characteristics represented by ones, not decimated by said decimating means, of said pilot signals extracted by said extracting means.

4. A demodulating method comprising the steps of:

performing Fast Fourier Transform (FFT) process on an Orthogonal Frequency Division Multiplexing (OFDM) time-domain signal;

removing an intercarrier interferential component from an OFDM frequency-domain signal which is produced when the FFT process is performed on the OFDM time-domain signal;

extracting pilot signals representative of transmission path characteristics of a transmission path from said OFDM frequency-domain signal from which the intercarrier interferential component is removed;

estimating transmission path characteristics represented by subsequently received pilot signals, based on the transmission path characteristics represented by the extracted pilot signals;

interpolating transmission path characteristics in a frequency direction based on the estimated transmission path characteristics thereby to estimate transmission path characteristics for all subcarriers;

estimating a symbol sequence represented by said OFDM frequency-domain signal which is produced when the FFT process is performed on the OFDM time-domain signal, based on the estimated transmission path characteristics for all subcarriers; and

generating an interference replica representing said intercarrier interferential component to be removed from said OFDM frequency-domain signal, based on the estimated symbol sequence and the estimated transmission path characteristics for all subcarriers.

5. A non-transitory computer-readable storage medium on which is recorded a program for enabling a computer to perform a process including the steps of:

performing a Fast Fourier Transform (FFT) process on an Orthogonal Frequency Division Multiplexing (OFDM) time-domain signal;

removing an intercarrier interferential component from an OFDM frequency-domain signal which is produced when the FFT process is performed on the OFDM time-domain signal;

extracting pilot signals representative of transmission path characteristics of a transmission path from said OFDM frequency-domain signal from which the intercarrier interferential component is removed;

estimating transmission path characteristics represented by subsequently received pilot signals, based on the transmission path characteristics represented by the extracted pilot signals;

interpolating transmission path characteristics in a frequency direction based on the estimated transmission path characteristics thereby to estimate transmission path characteristics for all subcarriers;

estimating a symbol sequence represented by said OFDM frequency-domain signal which is produced when the FFT process is performed on the OFDM time-domain signal, based on the estimated transmission path characteristics for all subcarriers; and

generating an interference replica representing said intercarrier interferential component to be removed from said OFDM frequency-domain signal, based on the estimated symbol sequence and the estimated transmission path characteristics for all subcarriers.

6. A receiving device comprising:

Fast Fourier Transform (FFT) processing means for performing an FFT process on an Orthogonal Frequency Division Multiplexing (OFDM) time-domain signal;

intercarrier interferential component removing means for removing an intercarrier interferential component from an OFDM frequency-domain signal which is produced when the FFT process is performed on the OFDM time-domain signal by said FFT processing means;

extracting means for extracting pilot signals representative of transmission path characteristics of a transmission path from said OFDM frequency-domain signal from which the intercarrier interferential component is removed by said intercarrier interferential component removing means;

transmission path characteristics estimating means for estimating transmission path characteristics represented by subsequently received pilot signals, based on the transmission path characteristics represented by said pilot signals extracted by said extracting means;

interpolating means for interpolating transmission path characteristics in a frequency direction based on the transmission path characteristics estimated by said transmission path characteristics estimating means thereby to estimate transmission path characteristics for all subcarriers;

symbol sequence estimating means for estimating a symbol sequence represented by said OFDM frequency-domain signal which is produced when the FFT process is performed on the OFDM time-domain signal by said FFT processing means, based on the transmission path characteristics for all subcarriers which are estimated by said interpolating means; and

interference replica generating means for generating an interference replica representing said intercarrier interferential component to be removed from said OFDM frequency-domain signal by said intercarrier interferential component removing means, based on the symbol sequence estimated by said symbol sequence estimating means and the transmission path characteristics for all subcarriers which are estimated by said interpolating means.

7. A demodulating circuit comprising:

Fast Fourier Transform (FFT) processing section configured to perform an FFT process on an Orthogonal Frequency Division Multiplexing (OFDM) time-domain signal;

an intercarrier interferential component removing section configured to remove an intercarrier interferential component from an OFDM frequency-domain signal which is produced when the FFT process is performed on the OFDM time-domain signal by said FFT processing section;

an extracting section configured to extract pilot signals representative of transmission path characteristics of a transmission path from said OFDM frequency-domain signal from which the intercarrier interferential component is removed by said intercarrier interferential component removing section;

a transmission path characteristics estimating section configured to estimate transmission path characteristics represented by subsequently received pilot signals, based on the transmission path characteristics represented by said pilot signals extracted by said extracting section;

an interpolating section configured to interpolate transmission path characteristics in a frequency direction based on the transmission path characteristics estimated by said transmission path characteristics estimating section thereby to estimate transmission path characteristics for all subcarriers;

a symbol sequence estimating section configured to estimate a symbol sequence represented by said OFDM frequency-domain signal which is produced when the FFT process is performed on the OFDM time-domain signal by said FFT processing section, based on the transmission path characteristics for all subcarriers which are estimated by said interpolating section; and

an interference replica generating section configured to generate an interference replica representing said intercarrier interferential component to be removed from said OFDM frequency-domain signal by said intercarrier interferential component removing section, based on the symbol sequence estimated by said symbol sequence estimating section and the transmission path characteristics for all subcarriers which are estimated by said interpolating section.

8. A receiving device comprising:

a Fast Fourier Transform (FFT) processing section configured to perform an FFT process on an orthogonal Frequency Division Multiplexing (OFDM) time-domain signal;

an intercarrier interferential component removing section configured to remove an intercarrier interferential component from an OFDM frequency-domain signal which is produced when the FFT process is performed on the OFDM time-domain signal by said FFT processing section;

an extracting section configured to extract pilot signals representative of transmission path characteristics of a transmission path from said OFDM frequency-domain signal from which the intercarrier interferential component is removed by said intercarrier interferential component removing section;

a transmission path characteristics estimating section configured to estimate transmission path characteristics represented by subsequently received pilot signals, based on the transmission path characteristics represented by said pilot signals extracted by said extracting section;

an interpolating section configured to interpolate transmission path characteristics in a frequency direction based on the transmission path characteristics estimated by said transmission path characteristics estimating section thereby to estimate transmission path characteristics for all subcarriers;

a symbol sequence estimating section configured to estimate a symbol sequence represented by said OFDM frequency-domain signal which is produced when the FFT process is performed on the OFDM time-domain signal by said FFT processing section, based on the transmission path characteristics for all subcarriers which are estimated by said interpolating section; and

an interference replica generating section configured to generate an interference replica representing said intercarrier interferential component to be removed from said OFDM frequency-domain signal by said intercarrier interferential component removing section, based on the symbol sequence estimated by said symbol sequence estimating section and the transmission path characteristics for all subcarriers which are estimated by said interpolating section.