Orthogonal frequency division demodulator, method and computer program product
First Claim
1. An Orthogonal Frequency Division Multiplexing (OFDM) demodulator, comprising:
- an antenna configured to receive a signal including delayed signals;
an estimation circuit configured to estimate a channel response based on the signal received by the antenna;
a control circuit configured to control a length of a retention time interval based on the channel response estimated by the estimation circuit, the retention time interval including a time period between a first time when a head of a delayed signal having a maximum delay difference among the delayed signals is received and a second time when a tail of a preceding signal included in the signal received by the antenna is received;
a retention memory configured to retain a portion of the signal received by the antenna corresponding to the retention interval;
a symbol generation circuit configured to generate OFDM symbol candidates;
a conversion circuit configured to convert the OFDM symbol candidates into time domain signals;
a replica generation circuit configured to generate replica signals of the signal received by the antenna based on the time domain signals and the channel response estimated by the estimation circuit;
a calculation circuit configured to calculate likelihoods that the replica signals are equivalent to the portion of the signal retained in the retention memory; and
a selection circuit configured to select an OFDM symbol from the OFDM symbol candidates that corresponds to the replica signal having a maximum likelihood.
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Accused Products
Abstract
An OFDM demodulator that demodulates an OFDM signal includes an antenna that receives a signal including delayed signals, an estimation circuit that estimates the channel response of the received signal, and a control circuit that controls a length of a retention time interval based on the estimated channel response. The retention time interval includes a time period from the head of a delayed signal having a maximum delay time in the delayed signals to the tail of a preceding signal in the delayed signals based on the estimated channel response. The OFDM demodulator also includes a retention memory that retains a portion of the received signal corresponding to the retention time period, and a selection circuit that selects an OFDM symbol based on a calculation of a maximum likelihood that the retained received signal is equivalent to a signal replica based on the channel response.
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Citations
17 Claims
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1. An Orthogonal Frequency Division Multiplexing (OFDM) demodulator, comprising:
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an antenna configured to receive a signal including delayed signals;
an estimation circuit configured to estimate a channel response based on the signal received by the antenna;
a control circuit configured to control a length of a retention time interval based on the channel response estimated by the estimation circuit, the retention time interval including a time period between a first time when a head of a delayed signal having a maximum delay difference among the delayed signals is received and a second time when a tail of a preceding signal included in the signal received by the antenna is received;
a retention memory configured to retain a portion of the signal received by the antenna corresponding to the retention interval;
a symbol generation circuit configured to generate OFDM symbol candidates;
a conversion circuit configured to convert the OFDM symbol candidates into time domain signals;
a replica generation circuit configured to generate replica signals of the signal received by the antenna based on the time domain signals and the channel response estimated by the estimation circuit;
a calculation circuit configured to calculate likelihoods that the replica signals are equivalent to the portion of the signal retained in the retention memory; and
a selection circuit configured to select an OFDM symbol from the OFDM symbol candidates that corresponds to the replica signal having a maximum likelihood. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for demodulating an Orthogonal Frequency Division Multiplexing (OFDM) received signal including plural delayed signals received by an antenna, the method comprising:
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estimating a channel response based on the received signal;
controlling a length of a retention interval based on the estimated channel response, the retention interval including a time period between a first time when a head of a delayed signal having a maximum delay difference among the delayed signals is received and a second time when a tail of a preceding signal included in the received signal is received;
retaining a portion of the received signal corresponding to the retention interval;
generating OFDM symbol candidates;
converting the OFDM symbol candidates into time domain signals;
generating replica signals of the received signal based on the time domain signals and the estimated channel response;
calculating likelihoods that the replica signals are equivalent to the portion of the received signal retained in the retention memory; and
selecting an OFDM symbol from the OFDM symbol candidates that corresponds to the replica signal having a maximum likelihood.
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17. A computer program product storing a program which, when executed by a processor in an apparatus configured to demodulate an Orthogonal Frequency Division Multiplexing (OFDM) received signal including plural delayed signals received by an antenna, causes the processor to perform steps comprising:
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estimating a channel response based on the received signal;
controlling a length of a retention interval based on the estimated channel response, the retention interval including a time period between a first time when a head of a delayed signal having a maximum delay difference among the delayed signals is received and a second time when a tail of a preceding signal included in the received signal is received;
retaining a portion of the received signal corresponding to the retention interval;
generating OFDM symbol candidates;
converting the OFDM symbol candidates into time domain signals;
generating replica signals of the received signal based on the time domain signals and the estimated channel response;
calculating likelihoods that the replica signals are equivalent to the portion of the received signal retained in the retention memory; and
selecting an OFDM symbol from the OFDM symbol candidates that corresponds to the replica signal having a maximum likelihood.
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Specification