Method and apparatus for transmitting uplink signals using multi-antenna

A user equipment (UE) for transmitting uplink signals, the UE comprising:

• multiple antennas for transmitting and receiving signals;
• a memory for storing a codebook;
• a processor connected to the multiple antennas and the memory to process transmission of the uplink signals,
• wherein the processor includes:
• a layer mapper for mapping the uplink signals to a predetermined number of layers corresponding to a specific rank;
• Discrete Fourier Transform (DFT) modules for performing, after the mapping, DFT spreading for each of the predetermined number of layers;
• a precoder for precoding each of the DFT-spread layers using a specific precoding matrix selected from the codebook to produce precoded signals, wherein the codebook comprises a plurality of precoding matrixes, wherein every precoding matrix of the codebook is established in a manner to permit each one of the multiple antennas to transmit no more than one layer of the DFT-spread layers;
• and
• a transmission module for performing a process for constructing a Single Carrier-Frequency Division Multiple Access (SC-FDMA) symbol upon the precoded signals, and transmitting the processed signals to a base station (BS) via the multiple antennas,
• wherein the codebook stored in the memory includes a Rank 2 precoding matrix utilized when the number of the multiple antennas is 4 and the rank is set to 2, wherein Rank 2 precoding matrix includes a first type precoding matrix being configured in a form of
• [
• 1
• 0
• X
• 0
• 0
• 1
• 0
• Y
• ]
• ,
• a second type precoding matrix configured in a form of
• [
• 1
• 0
• 0
• 1
• X
• 0
• 0
• Y
• ]
• ,
• and a third type precoding matrix configured in a form of
• [
• 1
• 0
• 0
• 1
• 0
• Y
• X
• 0
• ]
• ,
• and satisfying a condition of
• X
• ,
• Y
• ∈
• {
• 1
• ,
• 1
• +
• j
• 2
• ,
• j
• ,
• 1
• -
• j
• 2
• ,
• -
• 1
• ,
• -
• 1
• -
• j
• 2
• ,
• -
• j
• ,
• -
• 1
• +
• j
• 2
• }
• wherein individual rows of the Rank 2 precoding matrix respectively correspond to four antennas of the multiple antennas, and individual columns of the Rank 2 precoding matrix respectively correspond to layers.