Patent ID: 8121075

Claim:
A base station which utilizes a multi-user multi-input and multi-output (MIMO) method, comprising: a storing means, for storing codebook vector group information relevant to a combination of codebook vectors configured to be used as a pre-coding group, the codebook vector group information comprising an index of the combination of codebook vectors configured to be used as a pre-coding group; a pre-coding matrix element selecting means, for selecting codebook vectors to be taken as elements of a pre-coding matrix; a pre-coding matrix index determining means, for determining an index, to which a combination of the codebook vectors selected by the pre-coding matrix element selecting means corresponds, in accordance with the codebook vectors to be taken as elements of a pre-coding matrix as selected by the pre-coding matrix element selecting means and with reference to the codebook vector group information; and a pre-coding matrix index transmitting means, for transmitting the index of the combination of the codebook vectors determined by the pre-coding matrix index determining means.