Method and apparatus for efficient feedback in a wireless communication system supporting multiple antennas

A method for receiving channel status information (CSI) via uplink in a wireless communication system, the method comprising:

• receiving a rank indicator (RI) at a first subframe, wherein the RI is Rank-1, Rank-2, Rank-3, Rank-4, Rank-5, Rank-6, or Rank-7;
• and
• receiving a wideband channel quality indicator (WB CQI), a first wideband precoding matrix indicator (WB PMI) and a second WB PMI at a second subframe,
• wherein, if the RI is Rank-1 or Rank-2, a number of elements for the first WB PMI is 8 and a number of elements for the second WB PMI is 2, and
• wherein, if the RI is Rank-5, Rank-6, or Rank-7, a number of elements for the first WB PMI is 4and a number of elements for the second WB PMI is 1.

A user equipment (UE) for transmitting channel status information (CSI) via uplink in a wireless communication system, the UE comprising:

• a reception module for receiving a downlink signal from a base station (BS);
• a transmission module for transmitting an uplink signal to the BS;
• and
• a processor for controlling the UE including the reception module and the transmission module,
• wherein the processor is configured to:
• transmit, via the transmission module, a rank indicator (RI) at a first subframe, wherein the RI is Rank-1, Rank-2, Rank-3, Rank-4, Rank-5, Rank-6, or Rank-7;
• and
• transmit, via the transmission module, a wideband channel quality indicator (WB CQI), a first wideband precoding matrix indicator (WB PMI) and a second WB PMI at a second subframe,
• wherein, if the RI is Rank-1 or Rank-2, a number of elements for the first WB PMI is 8 and a number of elements for the second WB PMI is 2, and
• wherein, if the RI is Rank-5, Rank-6, or Rank-7, a number of elements for the first WB PMI is 4 and a number of elements for the second WB PMI is 1.

A base station (BS) for receiving channel status information (CSI) via uplink in a wireless communication system, the BS comprising:

• a reception module for receiving an uplink signal from a user equipment (UE);
• a transmission module for transmitting a downlink signal to the UE;
• and
• a processor for controlling the BS including the reception module and the transmission module,
• wherein the processor is configured to:
• receive, via the reception module, a rank indicator (RI) at a first subframe, wherein the RI is Rank-1, Rank-2, Rank-3, Rank-4, Rank-5, Rank-6, or Rank-7;
• and
• receive, via the reception module, a wideband channel quality indicator (WB CQI), a first wideband precoding matrix indicator (WB PMI) and a second WB PMI at a second subframe,
• wherein, if the RI is Rank-1 or Rank-2, a number of elements for the first WB PMI is 8 and a number of elements for the second WB PMI is 2, and
• wherein, if the RI is Rank-5, Rank-6, or Rank-7, a number of elements for the first WB PMI is 4 and a number of elements for the second WB PMI is 1.