Patent ID: 8625698

Claim:
A method for transmitting channel status information (CSI) of downlink transmission via uplink in a wireless communication system, the method comprising: transmitting a rank indicator (RI) at a first subframe; and transmitting a first precoding matrix indicator (PMI), a second PMI, and a wideband (WB) channel quality indicator (CQI) at a second subframe, wherein a user equipment (UE) preferred precoding matrix is indicated by a combination of the first PMI and the second PMI, and a subsampled codebook for each precoding codebook of ranks from Rank-1 to Rank-4 is applied to the first PMI and the second PMI, and a sum of the first PMI and the second PMI for each of Rank-1 to Rank-4 is comprised of 4 bits.