A Multiple-Input Multiple-Output (MIMO) communication system and method. The MIMO communication system includes: an antenna number determination unit to determine a number of active antennas among a plurality of transmitting antennas based on a power of a transmission signal wherein the number of active antennas is at least one and the at least one active antenna transmits the transmission signal; and a beam generator to generate the transmission signal corresponding to the number of active antennas by using channel information wherein the channel information is fed back from each of a plurality of user terminals.