Patent ID: 8891651

Claim:
A method of reporting channel state information in a wireless communication system, the method performed by a transmitter and comprising: selecting a Mt×R precoding matrix in a codebook according to a rank indicating a number of layers; and reporting precoding matrix indication information indicating the selected Mt×R precoding matrix to a base station, wherein Mt denotes a number of antenna ports of the transmitter and R denotes the rank, wherein the codebook includes K Mt×R matrices, where K>1, wherein each of the K Mt×R matrices in the codebook is defined by P ⁡ ( k ) = ( w ⁢ ⁢ 1 ⁢ ( k ) · Q ⁢ ⁢ 1 ⁢ ( k ) w ⁢ ⁢ 1 ⁢ ( k ) · Q ⁢ ⁢ 2 ⁢ ( k ) w ⁢ ⁢ 2 ⁢ ( k ) · Q ⁢ ⁢ 3 ⁢ ( k ) - w ⁢ ⁢ 2 ⁢ ( k ) · Q ⁢ ⁢ 4 ⁢ ( k ) ) , wherein P(k) denotes a k-th matrix in the codebook, k=1, ..., K, Q 1 (k) denotes a first element matrix for the k-th matrix, Q 2 (k) denotes a second element matrix for the k-th matrix, Q 3 (k) denotes a third element matrix for the k-th matrix, and Q 4 (k) denotes a fourth element matrix for the k-th matrix, wherein w 1 (k) denotes a weight for the first and second element matrices, and w 2 (k) denotes a weight for the third and fourth element matrices, wherein each of the first, second, third, and fourth element matrices has Nt rows, where Nt=Mt/2.