Patent ID: 7917176

Claim:
A method of performing multi-rank, quantized beamforming comprising: estimating a channel between a beamforming transmitter and a receiver at the receiver; determining a beamforming rank based on the channel estimate; determining a power allocation for each of a plurality of signal streams; determining a quantized beamforming matrix; providing an indication of the power allocation and quantized beamforming matrix to the beamforming transmitter; and transmitting the plurality of signal streams from the beamforming transmitter to the receiver in accordance with the power allocation and quantized beamforming matrix, wherein the beamforming transmitter has M antennas and the quantized beamforming matrix is selected from a codebook comprising codebook entries V in the form: V = [ v 1 , Φ ⁡ ( v 1 1 ) ⁢ HH ⁡ ( v 1 Φ ⁡ ( v 1 1 ) - ⅇ 1 M ) ⁡ [ 0 v 2 ] , Φ ⁡ ( v 1 1 ) ⁢ HH ⁡ ( v 1 Φ ⁡ ( v 1 1 ) - ⅇ 1 M ) ⁡ [ Φ ⁡ ( v 1 2 ) ⁢ HH ⁡ ( v 2 0 Φ ⁡ ( v 1 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, v b a denotes the b th element of the vector v a , Φ ⁡ ( v b a ) = v b a  v b a  , ⁢ and H ⁡ ( w ) = I - 2 ⁢ ww T  w  2 .