1. A method of transmitting channel state information in user equipment including a transceiver, the method comprising: extracting one or more reference vectors having a high correlation with a channel state information vector associated with a downlink; creating one or more compressed vectors by compressing the one or more reference vectors; and transmitting, by the transceiver, the one or more compressed vectors, wherein: the correlation is calculated by multiplying a square matrix by the channel state information vector, where columns of the square matrix are orthogonal to each other; and the reference vectors are column vectors having a high correlation in the square matrix.