A method for efficiently providing data and a reference signal (RS) when antennas are added to an existing system is provided. The method includes transmitting an RS in a downlink MIMO system that supports a first user equipment (UE) and a second UE, the first UE recognizing four predetermined transmitting antennas among eight transmitting antennas and the second UE recognizing the eight transmitting antennas, generating a subframe that can be recognized by both the first UE and the second UE and transmitting the generated subframe to the first UE and the second UE, where the first UE and the second UE recognize all orthogonal frequency division multiplexing (OFDM) symbols of the subframe.