Patent ID: 8761129

Claim:
A method implemented in a user equipment configured to be used in a multi-user (MU) multiple-input multiple-output (MIMO) wireless communications system, the method comprising: transmitting to a base station a first channel state information (CSI) report determined according to a single-user (SU) MIMO rule; and transmitting to the base station a second CSI report based on a residual error, wherein the second CSI report includes an indication or a quantized value of a dominant diagonal value of R 1 along with a corresponding column in Q 1 where Q 1 is a semi-unitary matrix whose columns lie in the orthogonal complement of {circumflex over (V)} 1 , {circumflex over (V)} 1 being a semi-unitary matrix whose columns represent preferred channel directions, and R 1 is a matrix which satisfies the Frobenius-norm constraint ∥R 1 ∥ F 2 ≦ε 1 2 , ε 1 being the residual error norm.