Data transmission device and method in a wireless communications system

A method of reporting channel state information in a wireless communication system, the method comprising:

• determining an rank indicating a number of layers;
• selecting an Mt×R precoding matrix in a codebook according to the rank;
• and
• reporting a precoding matrix indicator indicating the selected Mt×R precoding matrix to a base station,
• wherein Mt denotes a number of antenna ports and R denotes the rank,
• wherein the codebook includes K Mt×R matrices, where K≧1, and
• wherein each of the K Mt×R matrices is defined based on at least an element matrix.

An apparatus for reporting channel state information in a wireless communication system, the apparatus comprising a processor configured for:

• determining a rank indicating a number of layers;
• selecting an Mt×R precoding matrix in a codebook according to the rank;
• and
• reporting a precoding matrix indicator indicating the selected Mt×R precoding matrix to a base station,
• wherein Mt denotes a number of antenna ports and R denotes the rank,
• wherein the codebook includes K Mt×R matrices, where K≧1, and
• wherein each of the K Mt×R matrices is defined based on at least an element matrix.

An apparatus for transmitting data in a wireless communication system, the apparatus comprising a processor configured for:

• selecting an Mt×R precoding matrix in a codebook according to a rank;
• and
• transmitting data by using the selected Mt×R precoding matrix through M antennas to at least one user equipment,
• wherein Mt denotes a number of antenna ports and R denotes the rank,
• wherein the codebook includes K M×R matrices, where K≧1, and
• wherein each of the K Mt×R matrices is defined based on at least an element matrix.