Patent ID: 7502311

Claim:
A method for detecting by a mobile station a cell in which the mobile station is located in an Orthogonal Frequency Division Multiple Access (OFDMA) system, the method comprising the steps of: receiving a signal including a base station's PN code from the base station and performing fast Fourier transform (FFT) on the received signal thereby generating an FFT-processed signal; generating a test PN code for comparison with the base station's PN code; and detecting a cell where the mobile station is located by searching for a PN code synchronized in the FFT-processed signal using the test PN code using one of a first cell detecting step, a second cell detecting step, and a third cell detecting step; wherein the first cell detecting step comprises the steps of: dividing the FFT-processed signal by a signal corresponding to the test PN code thereby generating a divided signal; performing inverse fast Fourier transform (IFFT) on the divided signal thereby generating an IFFT-processed signal; and determining whether the test PN code is synchronized with a PN code for the IFFT-processed signal, the test PN code being synchronized with the PN code for the IFFT-processed signal when a channel region's dispersion for the IFFT-processed signal is a maximum value; wherein the second cell detecting step comprises the steps of: dividing the FFT-processed signal by the signal corresponding to the test PN code thereby generating a divided signal; filtering the divided signal using a frequency-domain filter to discriminate between a channel region and a noise region thereby generating a filtered signal; and determining whether the test PN code is synchronized with a PN code for the filtered signal, the test PN code being synchronized with the PN code for the filtered signal when a channel region's dispersion for the filtered signal is a maximum value; wherein the third cell detecting step comprises the steps of: performing IFFT on the FFT-processed signal to obtain a time-domain comparison signal; circular cross-correlating the time-domain comparison signal and a time-delayed time-domain comparison signal thereby generating a circular cross-correlated signal; and determining whether the test PN code is synchronized with a PN code for the circular cross-correlated signal, the test PN code being synchronized with the PN code for the circular cross-correlated signal when a channel region's dispersion for the circular cross-correlated signal is a maximum value.