Patent ID: 8238277

Claim:
A method for feeding back channel state information (CSI) in a closed-loop (CL) multiple-input, multiple-output (MIMO) wireless networks, wherein the network includes a plurality of cells, and each cell includes a base station (BS) and a set of mobile stations (MS), wherein each BS includes a set of N antennas spaced apart by at least half a carrier wavelength λ, and wherein the N antennas are associated with N subcarriers, comprising at each MS: determining a matrix R, wherein the matrix R is a transmit covariance matrix; applying a singular value decomposition (SVD) to the matrix R according to R=UΣV H , where U, V are left and right singular vector matrices, Σ is a diagonal matrix with singular values, the matrix V includes column vectors V, and H is a Hermitian operator; approximating a beamforming vector v max by the column vector V having a maximum magnitude, and wherein v max =[1exp( j Φ)exp( j 2Φ) . . . exp( j Φ)]/ √{square root over (N)}], where an angel Φ is a real number, and j indexes N; and feeding back, in analog form, from the MS to the BS, only the angle Φ using a phase modulation mapping of components exp(jΦ) of the vector v max onto the associated subcarrier.