Method for transmitting signal using multiple antennas

A method for transmitting signals, performed in a base station, comprising:

• transmitting reference signal for each antenna group and reference signal for each directional beam to a terminal;
• receiving a first precoder matrix index (PMI-1) and a second precoder matrix index (PMI-2), which are calculated based on the reference signals, from the terminal;
• and
• performing precoding on downlink data and reference signal for demodulation (DMRS) based a first precoder (P1) corresponding to the first precoder matrix index and a second precoder (P2) matrix corresponding to the second precoder matrix index.

A method for transmitting signals, performed in a base station, comprising:

• transmitting reference signals through directional beams formed by each of a plurality of antenna groups;
• receiving information on rank, a first precoder matrix index, and a second precoder matrix index of MIMO channels between the base station and a plurality of terminals which are determined based on the reference signals from the plurality of terminals;
• and
• determining MIMO transmission method for at least one of the plurality of terminals based on the information on rank, a first precoder matrix index, and a second precoder matrix index.

A method for transmitting cooperative signals, performed in a first base station and a second base station, comprising:

• determining, by a terminal, first precoder matrix indexes and second precoder matrix indexes for the first base station and the second base station based on reference signals transmitted for the first base station and the second base station, and reporting, by the terminal, the first precoder matrix indexes and the second precoder matrix indexes to the first base station or to the first and the second base stations;
• reporting, by the first base station, the first precoder matrix indexes and the second precoder matrix indexes to the second base station via an interface between the first and the second base stations;
• and
• performing, by the first and the second base stations, Single User MIMO (SU-MIMO) and Multi User MIMO (MU-MIMO) based on the first precoder matrix indexes and the second precoder matrix indexes.