Frequency synchronization apparatus and method in ofdm system

A frequency synchronization apparatus in an OFDM system, the apparatus comprising:

• a correlating unit that obtains a first correlation value by correlating a known reference guard interval of each OFDM symbol and a reference copy interval corresponding to the reference guard interval, sets an estimate guard interval from a pre-set point of the reference guard interval, and obtains a second correlation value by correlating the estimate guard interval and an estimate copy interval corresponding to the estimate guard interval;
• a determining unit that compares the first and second correlation values to determine a first case where the first correlation value is larger by a pre-set magnification than the second correlation value, a second case where the second correlation value is larger by a pre-set magnification than the first correlation value, and a third case which is not the first case nor the second case;
• an accumulating unit that accumulates the first correlation value by the pre-set symbol accumulation number in the event of the first case, accumulates the second correlation value by the pre-set symbol accumulation number in the event of the second case, and accumulates a value obtained by adding the first and second correlation values by the pre-set symbol accumulation number in the event of the third case;
• and
• a frequency offset estimating unit that estimates a frequency offset by using the correlation values accumulated by the accumulating unit.

A frequency synchronization method in an OFDM system, the method comprising:

• a correlating step of obtaining a first correlation value by correlating a known reference guard interval of an OFDM symbol and a reference copy interval corresponding to the reference guard interval, setting an estimate guard interval from a pre-set point of the reference guard interval, and obtaining a second correlation value by correlating the estimate guard interval and an estimate copy interval corresponding to the estimate guard interval;
• a determining step of comparing the first and second correlation values to determine a first case where the first correlation value is larger by a pre-set magnification than the second correlation value, a second case where the second correlation value is larger by a pre-set magnification than the first correlation value, and a third case which is not the first case nor the second case;
• an accumulating step of accumulating the first correlation value in the event of the first case, accumulating the second correlation value in the event of the second case, and accumulating a value obtained by adding the first and second correlation values in the event of the third case;
• and
• a frequency offset estimating step of estimating a frequency offset by using the correlation values accumulated in the accumulating step.