Circuit for synchronizing symbols of OFDM signal
A circuit for synchronizing symbols of a received OFDM signal includes a unit configured to detect cross-correlation of a received signal to generate a value of the cross-correlation, a unit configured to obtain synchronous summation of the value of the cross-correlation performed at predetermined intervals, a unit configured to obtain received electric power of the received signal, an autocorrelation electric power obtaining unit configured to obtain autocorrelation electric power of the received signal, a threshold obtaining unit configured to obtain a synchronous summation threshold responsive to the received electric power, and a symbol timing detecting unit configured to identify timing of a peak of the synchronous summation as symbol timing in response to detecting, at the timing of the peak, that the autocorrelation electric power is smaller than the received electric power multiplied by a predetermined factor and that the synchronous summation is larger than the synchronous summation threshold.
1. A circuit for synchronizing symbols of a received OFDM signal, comprising:
a cross-correlation detecting unit configured to detect cross-correlation of a received signal to generate a value of the cross-correlation;
a synchronous summation unit configured to obtain synchronous summation of the value of the cross-correlation performed at predetermined intervals;
a received electric power obtaining unit configured to obtain received electric power of the received signal;
an autocorrelation electric power obtaining unit configured to obtain autocorrelation electric power of the received signal;
a threshold obtaining unit configured to obtain a synchronous summation threshold responsive to the received electric power;
a symbol timing detecting unit configured to identify timing of a peak of the synchronous summation as symbol timing in response to detecting, at the timing of the peak, that the autocorrelation electric power obtained by the autocorrelation electric power obtaining unit is smaller than the received electric power, obtained by the received electric power obtaining unit, multiplied by a predetermined factor and that the synchronous summation is larger than the synchronous summation threshold that varies in response to the received electric power; and
a signal detecting unit configured to output a packet detection signal in response to detecting that the autocorrelation electric power obtained by the autocorrelation electric power obtaining unit stays larger than the received electric power, obtained by the received electric power obtaining unit, multiplied by a predetermined factor for more than a predetermined time period,
wherein said threshold obtaining unit includes a table that stores therein synchronous summation thresholds associated with respective received electric powers, and is configured to pick from the table the synchronous summation threshold associated with the received electric power for outputting therefrom.
2. The circuit as claimed in claim 1 , further comprising an AGC (auto gain control) control unit configured to perform AGC control based on the packet detection signal and the received electric power obtained by said received electric power obtaining unit.