Patent ID: 8743990

Claim:
A base station used in a wireless communications system, the base station comprising: a precoding unit to precode data with a precoding matrix based on a codebook which includes entries that are expressed as A ( v 1 , v 2 , v 3 , … ⁢ ) = [ v 1 , HH ⁡ ( v 1 - e 1 M ) ⁡ [ 0 v 2 ] , HH ⁡ ( v 1 - e 1 M ) ⁡ [ 0 HH ⁡ ( v 2 - e 1 M - 1 ) ⁡ [ 0 v 3 ] ] , … ⁢ ] , where the base station has M transmit antennas, e 1 N =[1,0 . . . , 0] T εC N (N=M, M−1, . . . ), C N being N-dimensional complex space, ν a denotes a column vector, and HH(ν k −e 1 l ) is a rotation matrix that transforms vector ν k to the unit vector e 1 i ; and a transmission unit to transmit the precoded data to a user equipment.