Abstract: Provided are a method and apparatus for performing a variable point Inverse Fast Fourier Transform (IFFT)/Fast Fourier Transform (FFT). The apparatus for performing a variable point IFFT includes: an IFFT interpolator generating interpolation data signals having a determined point and interpolating a plurality of interpolation data, the number of which depends on an IFFT operation mode signal into input data; an IFFT operator generating IFFT operation data signals by performing an IFFT operation for the interpolated data signals; an IFFT mode selector selecting and outputting some of the IFFT operation data signals in response to the IFFT operation mode signal so that the selected IFFT operation data have the same number of points as the input data; and a control unit outputting the IFFT operation. Therefore, it is possible to easily compute variably sized IFFT/FFT hardware.

Abstract: Provided are a training signal generation method using impulse trains encoded with orthogonal codes and a channel estimation method using an orthogonal code decoding in a Multiple-Input Multiple-Output-Orthogonal Frequency Division Multiplex (MIMO-OFDM) system. The channel estimation method using the orthogonal code decoding in the MIMO-OFDM system includes the steps of creating a plurality of orthogonal codes depending on the number of receive antennas, decoding a signal received through each receive antenna by using the orthogonal codes, and estimating a channel response by averaging the received signals decoded with the orthogonal codes every OFDM symbol.

Abstract: Provided are a method and apparatus for performing a variable point Inverse Fast Fourier Transform (IFFT)/Fast Fourier Transform (FFT). The apparatus for performing a variable point IFFT includes: an IFFT interpolator generating interpolation data signals having a determined point and interpolating a plurality of interpolation data, the number of which depends on an IFFT operation mode signal into input data; an IFFT operator generating IFFT operation data signals by performing an IFFT operation for the interpolated data signals; an IFFT mode selector selecting and outputting some of the IFFT operation data signals in response to the IFFT operation mode signal so that the selected IFFT operation data have the same number of points as the input data; and a control unit outputting the IFFT operation. Therefore, it is possible to easily compute variably sized IFFT/FFT hardware.

Abstract: An apparatus and method for canceling pilot signals from neighbor base stations is disclosed. The present invention cancels unnecessary pilot signals transmitted from the neighbor base stations by detecting, analyzing a PN signal in a pilot signal of each base station, generating estimated interference signal according to analyzed information from the detected PN signal and subtracting estimated interference signal from the received signal. Therefore, the present invention increases a bandwidth of downlink transmission channel and improves the demodulator to be operatable in low signal-to-noise ratio (Eb/No).

Abstract: An apparatus and method for canceling pilot signals from neighbor base stations is disclosed. The present invention cancels unnecessary pilot signals transmitted from the neighbor base stations by detecting, analyzing a PN signal in a pilot signal of each base station, generating estimated interference signal according to analyzed information from the detected PN signal and subtracting estimated interference signal from the received signal. Therefore, the present invention increases a bandwidth of downlink transmission channel and improves the demodulator to be operatable in low signal-to-noise ratio (Eb/No).

Abstract: This invention is directed to a method for increasing the probability of the success of handoff service in a mobile communication system. The present invention provides a handoff method for improving the talk quality in which a probability of the handoff success is raised and a probability of a call outage to disconnect a busy call is reduced.

Abstract: This invention is directed to a method for allocating a call in a CDMA base station. Whenever the base station receives a report of the change in the transmission power from channel processors, the level of interference affecting neighboring cells by a cell of its own is measured. In addition, when a new call is attempted, upon comparing the measured level of interference with a predetermined reference level (a threshold value) of interference, it is determined whether a call is allowed (i.e, allocated) or not dependent on a distance between the mobile station and the base station.