Patent ID: 8885754

Claim:
A method for transmitting a precoded signal by a transmitter in a wireless communication system supporting Multiple Input Multiple Output (MIMO) transmission, the method comprising: determining a first matrix (W 1 ) from a first codebook including precoding matrices indicated by a first precoding matrix index (PMI); determining a second matrix (W 2 ) from a second codebook including precoding matrices indicated by a second PMI; determining a precoding matrix (W) on the basis of the first matrix (W 1 ) and the second matrix (W 2 ); performing precoding of at least one layer mapped to a signal to be transmitted using the determined precoding matrix (W); and transmitting the precoded signal to the receiver, wherein each precoding matrix contained in the first codebook comprises a block diagonal matrix, wherein individual blocks of the block diagonal matrix are configured independently of each other, wherein each precoding matrix contained in the second codebook comprises an upper element and a lower element, where the lower element includes a phase rotation value, and wherein: an i-th precoding matrix W 1 ( i ) from among precoding matrices contained in the first codebook and a j-th precoding matrix W 2 ( j ) from among precoding matrices contained in the second codebook are represented by the following equation: W ⁢ ⁢ 1 ⁢ ( i ) = [ X i 0 0 Y i ] ⁢ ⁢ W ⁢ ⁢ 2 ⁢ ( j ) = [ e M k ⁢ e M l ⁢ … e M n ⁢ α j ⁢ e M k ⁢ β j ⁢ e M l ⁢ … γ j ⁢ e M n ⁢ ] , [ Equation ] where W 1 ( i ) is a (Nt×2M)-sized block diagonal matrix, Xi and Yi are individual blocks of the block diagonal matrix, each of Xi and Yi is a (Nt/2)×M-sized matrix, and Nt is the number of transmission antennas of the transmitter, where W 2 ( j ) is a (2M×r)-sized matrix, r is the number of the layers, e M p (p=k, l, . . . , n) is a (M×1)-sized vector, a p-th component from among M vector components of e M p is set to 1, the remaining components other than the p-th component are set to “0”, e M k , e M l , . . . , e M n denote the upper elements, α j e M k , β j e M l , . . . , γ j e M n denote the lower elements, and α j , β j , γ j denote the phase rotation values, and where k, l, n are 1≦k, l, n≦M, and k, l, and n are integers, respectively.