OFDM demodulation device
View Patent ↗A delay indicator calculator calculates at least two of a first delay indicator indicating a delay time determined based on a correlation value having a predetermined difference from the maximum value of the correlation signal, a second delay indicator indicating a change of a delay time determined based on time during which the correlation signal has no less than a predetermined value, and a third delay indicator indicating a change of a time difference between main and delay path peaks. An estimator generates a state estimation of the transmission path based on the probabilities of the at least two delay indicator values exceeding respective reference values for a plurality of symbols.
1. A demodulation device for demodulating an Orthogonal Frequency Division Multiplexing (OFDM) signal received through a transmission path, the demodulation device comprising:
a correlator for detecting a correlation signal based on the OFDM signal;
a delay indicator calculator for calculating at least two of a plurality of delay indicator values including a first delay indicator value indicating a delay time interval determined based on a correlation value having a predetermined difference from a maximum peak value of the correlation signal in a symbol duration of the OFDM signal, a second delay indicator value indicating a change of a delay time interval determined based on a time during which a value of the correlation signal is equal to or greater than a predetermined correlation value in the symbol duration of the OFDM signal, and a third delay indicator value indicating a change of a time difference between a main path peak and a delay path peak in the symbol duration of the OFDM signal;
a delay indicator determinator for calculating respective probabilities of the at least two delay indicator values exceeding respective reference values in a plurality of symbol durations of the OFDM symbol; and
a transmission path state estimator for generating a state estimation value of the transmission path based on the respective probabilities of the at least two delay indicator values.
2. The demodulation device according to claim 1 , wherein the delay indicator determinator calculates respective probabilities of the first to third delay indicator values exceeding respective reference values and the transmission path state estimator performs weighted calculation on the respective probabilities to generate the state estimation value of the transmission path.
3. The demodulation device according to claim 1 , wherein the transmission path state estimator estimates a noise state of the transmission path by performing weighted calculation on respective probabilities of the first and second delay indicator values exceeding respective reference values and estimates a state regarding movement speed of the demodulation device based on a probability of the third delay indicator value exceeding a predetermined threshold value.
4. The demodulation device according to claim 1 , wherein
the delay indicator calculator calculates a fourth delay indicator value indicating a magnitude of a gradient of a correlation waveform based with regard to a main path peak and the delay path peak in the symbol duration of the OFDM signal,
the delay indicator determinator calculates respective probabilities of the first to fourth delay indicator values exceeding respective reference values, and
the transmission path state estimator generates a state estimation value of the transmission path based on the respective probabilities of the first to fourth delay indicator values.
5. The demodulation device according to claim 4 , wherein the delay indicator calculator includes a statistical calculation unit that calculates the first to fourth delay indicator values through statistical calculation.
6. The demodulation device according to claim 4 , wherein the transmission path state estimator estimates a noise state of the transmission path, a state regarding movement speed of the demodulation device, and a state regarding a received signal level of the OFDM signal.
7. The demodulation device according to claim 1 , further comprising an OFDM demodulator that switches between demodulation operation modes based on the state estimation value.
8. A demodulation device for demodulating an Orthogonal Frequency Division Multiplexing (OFDM) signal received through a transmission path, the demodulation device comprising:
a correlator for detecting a correlation signal based on the OFDM signal;
a delay indicator calculator for calculating at least two of a plurality of delay indicator values including a first delay indicator value indicating a delay time interval determined based on a correlation value having a predetermined difference from a maximum peak value of the correlation signal in a symbol duration of the OFDM signal, a second delay indicator value indicating a change of a delay time interval determined based on a time during which a value of the correlation signal is equal to or greater than a predetermined correlation value in the symbol duration of the OFDM signal, a third delay indicator value indicating a change of a time difference between a main path peak and a delay path peak in the symbol duration of the OFDM signal, and a fourth delay indicator value indicating a magnitude of a gradient of a correlation waveform based with regard to a main path peak and the delay path peak in the symbol duration of the OFDM signal;
a delay indicator determinator for calculating respective probabilities of the at least two delay indicator values exceeding respective reference values in a plurality of symbol durations of the OFDM symbol; and
a transmission path state estimator for generating a state estimation value of the transmission path based on the respective probabilities of the at least two delay indicator values.
9. The demodulation device according to claim 8 , wherein the delay indicator determinator calculates respective probabilities of the first to fourth delay indicator values exceeding respective reference values and the transmission path state estimator performs weighted calculation on the respective probabilities to generate the state estimation value of the transmission path.
10. The demodulation device according to claim 8 , wherein the delay indicator calculator includes a statistical calculation unit that calculates the first to fourth delay indicator values through statistical calculation.
11. The demodulation device according to claim 8 , wherein the transmission path state estimator estimates a noise state of the transmission path, a state regarding movement speed of the demodulation device, and a state regarding a received signal level of the OFDM signal.
12. The demodulation device according to claim 8 , further comprising an OFDM demodulator that switches between demodulation operation modes based on the state estimation value.
13. A method for demodulating an Orthogonal Frequency Division Multiplexing (OFDM) signal received through a transmission path, the method comprising:
detecting a correlation signal based on a received OFDM signal;
a delay indicator calculating step of calculating at least two of a plurality of delay indicator values including a first delay indicator value indicating a delay time interval determined based on a correlation value having a predetermined difference from a maximum peak value of the correlation signal in a symbol duration of the OFDM signal, a second delay indicator value indicating a change of a delay time interval determined based on a time during which a value of the correlation signal is equal to or greater than a predetermined correlation value in the symbol duration of the OFDM signal, and a third delay indicator value indicating a change of a time difference between a main path peak and a delay path peak in the symbol duration of the OFDM signal;
a delay indicator determining step of calculating respective probabilities of the at least two delay indicator values exceeding respective reference values in a plurality of symbol durations of the OFDM symbol; and
a transmission path state estimating step of generating a state estimation value of the transmission path based on the respective probabilities of the at least two delay indicator values.
14. The method according to claim 13 , wherein,
the delay indicator determining step calculates respective probabilities of the first to third delay indicator values exceeding respective reference values, and
the transmission path state estimating step performs weighted calculation on the respective probabilities to generate the state estimation value of the transmission path.
15. The method according to claim 13 , wherein the transmission path state estimating step estimates a noise state of the transmission path by performing weighted calculation on respective probabilities of the first and second delay indicator values exceeding respective reference values and estimates a state regarding movement speed of the demodulation device based on a probability of the third delay indicator value exceeding a predetermined threshold value.