Signal transmission method and apparatus using codebook in wireless communication system supporting multiple antennas

A method for transmitting downlink signal using 2·N (N being a natural number>0) transmit Tx antennas by a base station (BS) in a Multiple-Input Multiple-Output (MIMO) system, the method comprising:

• mapping, by the BS, the downlink signal to R layers;
• precoding, by the BS, the downlink signal mapped to the R layers by applying a precoding matrix in a pre-stored codebook;
• and
• transmitting, by the BS, the precoded downlink signal to a user equipment (UE) through 2·N Tx antennas,
• wherein the codebook includes precoding matrices configured in the form of
• [
• W
• 1
• W
• 1
• aW
• 1
• -
• aW
• 1
• ]
• ,
• wherein W1 is an N×(R/2) matrix and a is a coefficient of a phase,
• wherein R is an even number,
• wherein when R is equal to 4 (R=4), the precoding matrices are configured in the form of
• [
• v
• ⁢
• ⁢
• 1
• v
• ⁢
• ⁢
• 2
• v
• ⁢
• ⁢
• 1
• v
• ⁢
• ⁢
• 2
• a
• ·
• v
• ⁢
• ⁢
• 1
• a
• ·
• v
• ⁢
• ⁢
• 2
• -
• a
• ·
• v
• ⁢
• ⁢
• 1
• -
• a
• ·
• v
• ⁢
• ⁢
• 2
• ]
• ,
• ⁢
• and
• wherein v1 is an N×1 matrix and v2 is an N×1 matrix.

A user equipment (UE) for transmitting a precoding matrix indicator (PMI) in a Multiple-Input Multiple-Output system, the UE comprising:

• a reception (Rx) module;
• a transmission (Tx) module;
• a memory;
• and
• a processor;
• wherein the processor is configured to determine a precoding matrix applicable to a downlink transmission from a base station (BS) in a pre-stored codebook,
• wherein the Tx module is configured to transmit at least one PMI corresponding to the determined precoding matrix to the BS,
• wherein the codebook includes precoding matrices applicable to a downlink transmission of R layers transmitted by the base station through 2·N (N being a natural number>0) transmit (Tx) antennas, and
• wherein the codebook includes precoding matrices configured in the form of
• [
• W
• 1
• W
• 1
• aW
• 1
• -
• aW
• 1
• ]
• ,
• wherein W1 is an N×(R/2) matrix and a is a coefficient of a phase,
• wherein R is an even number,
• wherein when R is equal to 4 (R=4), the precoding matrices are configured in the form of
• [
• v
• ⁢
• ⁢
• 1
• v
• ⁢
• ⁢
• 2
• v
• ⁢
• ⁢
• 1
• v
• ⁢
• ⁢
• 2
• a
• ·
• v
• ⁢
• ⁢
• 1
• a
• ·
• v
• ⁢
• ⁢
• 2
• -
• a
• ·
• v
• ⁢
• ⁢
• 1
• -
• a
• ·
• v
• ⁢
• ⁢
• 2
• ]
• ,
• ⁢
• and
• wherein v1 is an N×1 matrix and v2 is an N×1 matrix.

A base station (BS) for transmitting a downlink signal in a Multiple-Input Multiple-Output system, the BS comprising:

• 2·N (N being a natural number, N>0) transmit (Tx) antennas;
• a transmission (Tx) module for transmitting the downlink signal to a user equipment (UE) through the 2·N Tx antennas;
• a reception (Rx) module for receiving an uplink signal from a user equipment (UE);
• a memory for storing a codebook including a precoding matrix;
• and
• a processor for controlling the base station (BS),
• wherein the processor is configured to:
• map the downlink signal to R layers,
• perform precoding on the downlink signal mapped to the R layers by applying the precoding matrix in the pre-stored codebook, and
• control the Tx module to transmit the precoded downlink signal to the user equipment (UE) through 2·N Tx antennas, and
• wherein the codebook includes precoding matrices configured in the form of
• [
• W
• 1
• W
• 1
• aW
• 1
• -
• aW
• 1
• ]
• ,
• wherein W1 is an N×(R/2) matrix and a is a coefficient of a phase,
• wherein R is an even number,
• wherein when R is equal to 4 (R=4), the precoding matrices are configured in the form of
• [
• v
• ⁢
• ⁢
• 1
• v
• ⁢
• ⁢
• 2
• v
• ⁢
• ⁢
• 1
• v
• ⁢
• ⁢
• 2
• a
• ·
• v
• ⁢
• ⁢
• 1
• a
• ·
• v
• ⁢
• ⁢
• 2
• -
• a
• ·
• v
• ⁢
• ⁢
• 1
• -
• a
• ·
• v
• ⁢
• ⁢
• 2
• ]
• ,
• ⁢
• and
• wherein v1 is an N×1 matrix and v2 is an N×1 matrix.