Patent ID: 8233560

Claim:
A method implemented in a mobile terminal used in a wireless communications system and configured to receive precoded data from a remote transmitter, comprising: generating feedback information for transmission in order for the remote transmitter to select a precoding matrix from a codebook for M=4 transmit antennas having entries in the following form 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 e 1 N =[1, 0, . . . 0] T εC N , C N being N-dimensional complex space, v a denotes a column vector, HH(v k −e 1 l ) is a rotation matrix that transforms vector v k to the unit vector e 1 l and v a is selected from a set V a where V 1 =½{[1, 1, 1, 1] T , [1, −j, −1, j] T , [1, −1, 1, −1] T , [1, j, −1, −j] T , [1, f, −j, −g] T , [1, −g, j, f] T , [1, −f, −j, g] T , [1, g, j, −f] T , [1, 1, −1, −1] T , [1, −j, 1, −j] T , [1, −1, −1, 1] T , [1, j, 1, j] T , [1, 1, 1, −1] T , [1, 1, −1, 1] T , [1, −1, 1, 1] T , [1, −1, −1, −1] T }, f=(1−j)/√{square root over (2)}, g=(1+j)/√{square root over (2)}, j=√{square root over (−1)}, V 2 ={e 1 3 }, V 3 ={e 1 2 }, and V 4 ={e 1 1 }.