Patent ID: 8374562

Claim:
A transmitter used in a wireless communications system, the transmitter comprising: a precoding unit to precode a symbol with a precoding matrix selected from a codebook comprising a plurality of matrices; and a transmission unit to transmit to a receiver the precoded symbol using at least two transmit antennas, wherein the plurality of matrices have a nested structure and are in accordance with the following expression: A ( v i 1 1 , v i 2 2 , v i 3 3 , … ⁢ ) = [ v i 1 1 , H ⁡ ( v i 1 1 ⁢ ⁢ e 1 M ) ⁡ [ 0 v i 2 2 ] , ⁢ H ⁡ ( v i 1 1 ⁢ ⁢ e 1 M ) ⁡ [ 0 HH ⁡ ( v i 2 2 - e 1 M - 1 ) ⁡ [ 0 v i 3 3 ] ] , … ] , wherein e 1 N =[1,0, . . . , 0] T εC N , M is the number of transmit antennas, C N is an N-dimensional complex space, and HH ⁡ ( w ) = { I - 2 ⁢ ww H  w  2 if ⁢ ⁢ w ≠ 0 I if ⁢ ⁢ w = 0 and {v i j j εC M−j+1 } is a vector codebook, and wherein the wireless communications system comprises a multi-rank beamforming (MRBF) system.