Patent ID: 8532042

Claim:
A communication method of a transmitter for a multi-user multiple input multiple output (MIMO) communication system, the method comprising: maintaining a memory in which a first channel codebook corresponding to a first receiver and a second channel codebook corresponding to a second receiver are stored; receiving, from the first receiver, information associated with a first preferred codeword among codewords comprised in the first channel codebook, and receiving, from the second receiver, information associated with a second preferred codeword among codewords comprised in the second channel codebook; and determining a first beamforming vector for the first receiver from a first beamforming codebook and a second beamforming vector for the second receiver from a second beamforming codebook based on the first preferred codeword and the second preferred codeword, respectively, wherein the first channel codebook is different from the second channel codebook, the first channel codebook is different from the first beamforming codebook, and the second channel codebook is different from the second beamforming codebook, the first beamforming codebook is generated by performing an inner product with respect to a first unitary rotation matrix and each of codewords comprised in a pre-defined base codebook, and the second beamforming codebook is generated by performing an inner product with respect to a second unitary rotation matrix and each of the codewords comprised in the pre-defined base codebook, and the second unitary rotation matrix is different from the first unitary rotation matrix.