A frequency synchronization method of a receiver in a broadband wireless access communication system, the method comprising: acquiring a highest correlation value by conducting a differential correlation of a variable interval between a received signal and a reference signal; and performing a frequency synchronization according to the highest correlation value, wherein the acquiring of the highest correlation value by conducting the differential correlation of the variable interval between the received signal and the reference signal comprises the following steps being performed after a Fast Fourier Transform, FFT, processing: a first operation of multiplying the received signal, which is delayed by the variable interval by a complex conjugate of the received signal delayed by the variable interval and by a first delay signal; a second operation of multiplying a second signal, the second signal being delayed from the reference signal by the variable interval, by a complex conjugate of the reference signal in order to generate a output signal; a third operation of multiplying the output signal of the second operation by a complex conjugate of a second delay signal delayed from the output signal of the second operation by the variable interval; and a fourth operation of acquiring the highest correlation value among the set of first delay signal values by determining correlation values of an output signal of the first operation and an output signal of the third operation, and wherein the variable interval is determined based on the following equation: τ k = k mod S + 1 where mod denotes a modulo operation, a correlation interval iterates from a minimum of 1 to a maximum of S according to a subcarrier index, τ k denotes the variable interval, and S denotes a maximum correlation interval defined in consideration of a coherence bandwidth according to a channel environment. acquiring a highest correlation value by conducting a differential correlation of a variable interval between a received signal and a reference signal; and performing a frequency synchronization according to the highest correlation value, wherein the acquiring of the highest correlation value by conducting the differential correlation of the variable interval between the received signal and the reference signal comprises the following steps being performed after a Fast Fourier Transform, FFT, processing: a first operation of multiplying the received signal, which is delayed by the variable interval by a complex conjugate of the received signal delayed by the variable interval and by a first delay signal; a second operation of multiplying a second signal, the second signal being delayed from the reference signal by the variable interval, by a complex conjugate of the reference signal in order to generate a output signal; a third operation of multiplying the output signal of the second operation by a complex conjugate of a second delay signal delayed from the output signal of the second operation by the variable interval; and a fourth operation of acquiring the highest correlation value among the set of first delay signal values by determining correlation values of an output signal of the first operation and an output signal of the third operation, and wherein the variable interval is determined based on the following equation: τ k = k mod S + 1 where mod denotes a modulo operation, a correlation interval iterates from a minimum of 1 to a maximum of S according to a subcarrier index, τ k denotes the variable interval, and S denotes a maximum correlation interval defined in consideration of a coherence bandwidth according to a channel environment. a first operation of multiplying the received signal, which is delayed by the variable interval by a complex conjugate of the received signal delayed by the variable interval and by a first delay signal; a second operation of multiplying a second signal, the second signal being delayed from the reference signal by the variable interval, by a complex conjugate of the reference signal in order to generate a output signal; a third operation of multiplying the output signal of the second operation by a complex conjugate of a second delay signal delayed from the output signal of the second operation by the variable interval; and a fourth operation of acquiring the highest correlation value among the set of first delay signal values by determining correlation values of an output signal of the first operation and an output signal of the third operation, and wherein the variable interval is determined based on the following equation: τ k = k mod S + 1 where mod denotes a modulo operation, a correlation interval iterates from a minimum of 1 to a maximum of S according to a subcarrier index, τ k denotes the variable interval, and S denotes a maximum correlation interval defined in consideration of a coherence bandwidth according to a channel environment.