Patent ID: 8509332

Claim:
A base station apparatus, comprising a storage unit configured to store a codebook for an eight-antenna configuration, the codebook for the eight-antenna configuration comprising at least one rank-8 codeword for the eight-antenna configuration, the rank-8 codeword for the eight-antenna configuration being generated by extending rank-4 codewords for the eight-antenna configuration; a receiver configured to receive a label of a codeword from a user equipment (UE); a searching unit configured to select the codeword identified by the label from the codebook for the eight-antenna configuration; a coding unit configured to code data to be sent using the codeword selected by the searching unit; and a transmitter configured to send the coded data, wherein each rank-4 codeword for the eight-antenna configuration is generated by creating a matrix by multiplying the rank-4 codeword for a four-antenna configuration with a diagonal matrix and concatenating the rank-4 codeword for the four-antenna configuration and the matrix.