摘要
A method for receiving channel state information (CSI) by a base station, includes transmitting configuration information indicating whether to use a 4 antenna ports codebook, wherein a first codebook index for a first precoding matrix indicator (PMI) and a second codebook index for a second PMI for a specific CSI report mode with 4 antenna ports are determined when the UE is configured to use the 4 antenna ports codebook; and receiving the CSI indicating the first codebook index and the second codebook index, wherein a value of the first codebook index is determined as follows: when a rank indicator (RI) is 1, the value of the first codebook index is determined based on a value of the first PMI multiplied by 4, and when the RI is 2, the value of the first codebook index is determined based on the value of the first PMI multiplied by 4.