Patent ID: 8218423

Claim:
A ranging apparatus in an Orthogonal Frequency-Division Multiple Access (OFDMA) system, comprising: a correlation unit for correlating OFDMA reception signals with inverse fast Fourier transformed ranging codes, and outputting correlation result values; a threshold determination unit for determining a threshold value depending on characteristics of the reception signals input to the correlation unit; a comparison unit for estimating a delay time by selecting a maximum value from among the correlation result values output from the correlation unit, and detecting a ranging code by comparing the maximum value with the threshold value, and then outputting and feeding back the detected ranging code and the estimated delay time when the maximum value is equal to or greater than the threshold value; a weight multiplication unit for delaying the ranging code fed back from the comparison unit by the delay time, multiplying a weight by the delayed fed-back ranging code, and outputting a resulting value; and a calculation unit for subtracting the resulting value provided by the weight multiplication unit from the reception signals, and providing adjusted reception signals to the correlation unit.