Patent ID: 8611462

Claim:
A method for transmitting data using phase-shift-based precoding in a multiple antenna system, the method comprising: receiving feedback information including a subcarrier index offset and a phase value offset, wherein the phase value offset corresponds to a difference between a previously fed-back phase value and an optimized phase value and the subcarrier index offset indicates a subcarrier where a channel status is better than a channel status of a previous subcarrier; determining a diagonal matrix as a part of a phase-shift-based precoding matrix, wherein the diagonal matrix is determined by applying the subcarrier index offset and the phase value offset; selecting a first unitary matrix from a codebook as a part of the phase-shift-based precoding matrix; performing precoding using the phase-shift-based precoding matrix to symbols associated with the subcarrier indicated by the subcarrier index offset; and transmitting the precoded symbols, wherein the codebook comprises the first unitary matrix corresponding to a first spatial multiplexing rate and a second unitary matrix corresponding to a second spatial multiplexing rate, and wherein the second unitary matrix includes all columns of the first unitary matrix as a part of columns of the second unitary matrix when the second spatial multiplexing rate is higher than the first spatial multiplexing rate.