Method and apparatus for transmitting signals using codebooks in a wireless communication system that supports multiple antennas

A method of receiving a downlink signal, which is received by a user equipment, comprising the steps of:

• transmitting a 1st PMI (precoding matrix indicator) and a 2nd PMI to a base station;
• receiving a signal having a precoding performed on at least one layer having the downlink signal mapped thereto from the base station using a precoding matrix (W) determined based on a 1st matrix (W1) determined from a 1st codebook including precoding matrixes indicated by the 1st PMI and a 2nd matrix (W2) determined from a 2nd codebook including precoding matrixes indicated by the 2nd PMI;
• and
• processing the received downlink signal using the precoding matrix (W),
• wherein each of the precoding matrixes included in the 1st code book is configured with a block diagonal matrix and wherein one block is multiplied by a prescribed phase value while the other is not.

A base station, which transmits a downlink signal, comprising:

• a transmitting module transmitting a downlink signal to a user equipment;
• a receiving module receiving an uplink signal from the user equipment;
• a memory storing a codebook including precoding matrixes;
• and
• a processor controlling the base station, the processor configured to receive a 1st PMI (precoding matrix indicator) and a 2nd PMI from the user equipment via the receiving module,
• the processor configured to determine a 1st matrix (W1) from a 1st codebook including precoding matrixes indicated by the 1st PMI, determine a 2nd matrix (W2) from a 2nd codebook including precoding matrixes indicated by the 2nd PMI, and determine a precoding matrix (W) based on the 1st matrix (W1) and the 2nd matrix (W2),
• the processor configured to perform a precoding on at least one layer having the downlink signal mapped thereto using the determined precoding matrix (W),
• the processor configured to transmit the precoded signal to the user equipment,
• wherein each of the precoding matrixes included in the 1st code book is configured with a block diagonal matrix and wherein one block is multiplied by a prescribed phase value while the other is not.

A user equipment, which receives a downlink signal, comprising:

• a receiving module receiving the downlink signal from a base station;
• a transmitting module transmitting an uplink signal to the base station;
• a memory storing a codebook including precoding matrixes;
• and
• a processor controlling the user equipment,
• the processor configured to transmit a 1st PMI (precoding matrix indicator) and a 2nd PMI to the base station via the transmitting module,
• the processor configured to receive a signal having a precoding performed on at least one layer having the downlink signal mapped thereto from the base station via the receiving module using a precoding matrix (W) determined based on a 1st matrix (W1) determined from a 1st codebook including precoding matrixes indicated by the 1st PMI and a 2nd matrix (W2) determined from a 2nd codebook including precoding matrixes indicated by the 2nd PMI,
• the processor configured to process the received downlink signal using the precoding matrix (W),
• wherein each of the precoding matrixes included in the 1st code book is configured with a block diagonal matrix and wherein one block is multiplied by a prescribed phase value while the other is not.