Patent ID: 8229012

Claim:
A method of transmission implemented in a wireless communication system using precoding, comprising: precoding data using a precoding matrix based on a codebook which has 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 a transmitter has M=4 antennas, e 1 N =[1, 0, . . . , 0] T εC N (N=M, M−1, . . . ) , 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 = 1 2 ⁢ { [ 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 } , ⁢ where ⁢ ⁢ f = ( 1 - j ) / 2 , g = ( 1 + j ) / 2 , and ⁢ ⁢ j = - 1 , ⁢ V 2 = { e 1 3 } , V 3 = { e 1 2 } , ⁢ and ⁢ ⁢ V 4 = { e 1 1 } .