Patent ID: 8391393

Claim:
A method of transmitting a signal by a user equipment using 4 antennas, the method comprising: obtaining transmission rank information; generating a precoded signal by precoding layer signals using a specific precoding matrix that corresponds to the transmission rank information, transmitting the generated precoded signal, wherein the specific precoding matrix is selected from a 4-antenna codebook, the 4-antenna codebook including a first type precoding matrix defined as a 4-by-3 matrix type that includes 2 non-zero components in each row and 2 zero components in first and second columns for a rank of 3, wherein a number of the precoded layer signals corresponds to the transmission rank information, wherein the first type precoding matrix has a type resulting from multiplying W N t × 3 n = [ 1 0 1 ⅇ jθ 1 0 - ⅇ jθ 1 0 1 1 0 ⅇ jθ 2 - ⅇ jθ 2 ] ⁢ ⁢ or ⁢ ⁢ W N t × 3 n = [ 1 0 1 - ⅇ jθ 1 0 ⅇ jθ 1 0 ⅇ jθ 2 ⅇ jθ 2 0 - ⅇ jθ 3 ⅇ jθ 3 ] by a normalization coefficient, wherein N t is 4, wherein θ 1 , θ 2 meet a condition of θ 1 , θ 2 ∈ { 2 ⁢ π N ⁢ i , i = 0 , … ⁢ , N - 1 } , and wherein N is set to 4 or 8.