Patent ID: 7961808

Claim:
A method for transmitting signals at a transmitter of a Multi-Input Multi-Output (MIMO) system using a plurality of antennas, the method comprising: encoding input signals of an encoder to output one or more streams; performing a precoding on the one or more streams at a precoder to map the one or more streams to the plurality of antennas using a specific precoding matrix selected from a subset of a base codebook, wherein the base codebook includes (Nc) precoding matrices and the subset of the base codebook includes (N restrict ) precoding matrices, 1<(N restrict )<(Nc), and wherein the subset of the base codebook is predetermined to comprise of (N restrict ) precoding matrices having elements selected only from a group of ‘1’, ‘−1’, ‘j’, and ‘−j’; while the base codebook comprises precoding matrices having matrix elements other than the group of ‘1’, ‘−1’, ‘j’, and ‘−j’; and transmitting the antenna-mapped signals to a receiver.