Patent ID: 8340122

Claim:
A method for transmitting a reference signal for channel measurement in a downlink Multiple Input Multiple Output (MIMO) system which supports a first user equipment (UE) supporting N transmission antennas among a total of M transmission antennas (where M>N) and a second user equipment (UE) supporting the M transmission antennas, the method comprising: transmitting, by a base station (BS), subframe-associated information which designates a first subframe in which data for the first UE and the second UE is transmitted and a second subframe in which data only for the second UE is transmitted within a radio frame having a plurality of subframes; and transmitting the first subframe and the second subframe, wherein reference signals corresponding to antenna ports ‘0’ to ‘N−1’ of the N antennas are mapped to the first subframe, and reference signals corresponding to antenna ports ‘0’ to ‘M−1’ of the M antennas are mapped to the second subframe.