A transmission apparatus in a Multiple Input Multiple Output (MIMO)-based wireless communication system. The transmission apparatus includes at least two antenna groups each having at least two antennas, wherein the antenna groups are spaced apart by a first distance and transmit antennas in each antenna group are spaced apart by a second distance which is shorter than the first distance. A channel coding and modulation unit channel-codes and modulates a desired transmission data stream. A precoding unit precodes the channel-coded and modulated signal separately for each antenna group and each antenna in the same antenna group. Thereafter, a transmission processing unit transmission-processes the output signal from the precoding unit.