Patent ID: 8743989

Claim:
A method implemented in a user equipment used in a wireless communications system, the method comprising: precoding 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 user equipment 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 1 ) is a rotation matrix that transforms vector ν k to the unit vector e l 1 ; and transmitting the precoded data to a base station.