Abstract: Disclosed is a method for acquiring synchronization in a mobile communication system using an Orthogonal Frequency Division Multiplexing (OFDM) scheme. The method includes modeling a power delay profile in time-varying frequency selective fading channel conditions by a specific function; detecting a log probability distribution function of a timing offset and a frequency offset in consideration of a correlation between a received signal and the received multi-path signal in the time-varying frequency selective fading channel conditions having the power delay profile modeled as the specific function; and estimating a timing offset and a frequency offset which maximize the log probability distribution function of the timing offset and the frequency offset.

Abstract: In a method for feeding back combination information of transmitted signals in a multiple-input multiple-output (MIMO) system using a multiple space-time block coding technique, mean square error values are computed in relation to the combination information pieces of the transmitted signals. An index of a combination having a minimum mean square error value from among the mean square error values is fed back.

Abstract: A method of transmitting a signal by using an Adaptive Modulation and Coding scheme in a Frequency Hopping-Orthogonal Frequency Division Multiplexing Access communication system capable of dividing total frequency bands into a plurality of sub-carrier bands and including a plurality of sub-channels, which are sets of predetermined sub-carrier bands, and a plurality of cells. The method includes the steps of allocating a predetermined number of sub-channels as AMC sub-channels per each cell matching with predetermined conditions in order to apply the AMC scheme to the AMC sub-channels, and allocating remaining sub-channels except for the AMC sub-channels as FH-OFDMA sub-channels in order to apply an FH-OFDMA scheme to the FH-OFDMA sub-channels.