Method and apparatus for reporting a channel quality in a wireless communication system

1. A method for reporting channel quality by a device in a wireless communication system, the method comprising:

receiving, by the device, an uplink grant on a physical downlink control channel (PDCCH) through one of a plurality of downlink component carriers (CCs), the uplink grant including an uplink allocation and a channel quality indicator (CQI) request indicating a triggering of CQI reporting,

wherein, when a value of the CQI request is set to a first value, the CQI request indicates the triggering of CQI reporting is for one of the plurality of downlink CCs linked to an uplink CC, when the value of the CQI request is set to a second value, the CQI request indicates the triggering of CQI reporting is for a first set of downlink CCs of the plurality of downlink CCs, and when the value of the CQI request is set to a third value, the CQI request indicates the triggering of CQI reporting is for a second set of downlink CCs of the plurality of downlink CCs; and

reporting, by the device, a CQI for a downlink CC indicated by the CQI request through an uplink CC based on the uplink allocation.

2. The method of claim 1 , wherein the uplink grant further includes a carrier indicator field (CIF) indicating the uplink CC in which the uplink allocation is scheduled.

3. The method of claim 1 , wherein a number of bits for the CQI request is two.

4. The method of claim 1 , further comprising:

receiving information on the first set of downlink CCs and the second set of downlink CCs.

5. The method of claim 1 , wherein a linkage between the one of the plurality of downlink CCs linked to the uplink CC is received via system information.

6. The method of claim 1 , wherein the first value is “1,” the second value is “2,” and the third value is “3.”

7. An apparatus configured for reporting channel quality in a wireless communication system, the apparatus comprising:

a radio frequency (RF) unit configured to transmit and receive a radio signal; and

a processor coupled to the RF unit and configured to:

receive an uplink grant on a physical downlink control channel (PDCCH) through one of a plurality of downlink component carriers (CCs), the uplink grant including an uplink allocation and a channel quality indicator (CQI) request indicating a triggering of CQI reporting; wherein, when a value of the CQI request is set to a first value, the CQI request indicates the triggering of CQI reporting is for one of the plurality of downlink CCs linked to an uplink CC, when the value of the CQI request is set to a second value, the CQI request indicates the triggering of CQI reporting is for a first set of downlink CCs of the plurality of downlink CCs, and when the value of the CQI request is set to a third value, the CQI request indicates the triggering of CQI reporting is for a second set of downlink CCs of the plurality of downlink CCs; and

report a CQI for a downlink CC indicated by the CQI request through an uplink CC based on the uplink allocation.

8. The apparatus of claim 7 , wherein the uplink grant further includes a carrier indicator field (CIF) indicating the uplink CC in which the uplink allocation is scheduled.

9. The apparatus of claim 7 , wherein a number of bits for the CQI request is two.

10. The apparatus of claim 7 , wherein the processor is configured to receive information on the first set of downlink CCs and the second set of downlink CCs.

11. The apparatus of claim 7 , wherein a linkage between the one of the plurality of downlink CCs linked to the uplink CC is received via system information.

12. The apparatus of claim 7 , wherein the first value is “1,” the second value is “2,” and the third value is “3.”

13. A method for reporting a channel quality indicator (CQI) in a wireless communication system, the method comprising:

receiving, by a terminal configured with a plurality of downlink component carriers (CCs), control information via a physical downlink control channel (PDCCH) from a base station, the control information including an uplink allocation and a CQI request, the control information including a carrier indicator (CI) indicating an uplink CC in which the uplink allocation is scheduled; and

transmitting, by the terminal to the base station, the CQI via a physical uplink shared channel (PUSCH) of the uplink CC, based on the CQI request and the uplink allocation,

wherein the CQI request indicates one of:

a triggering of CQI reporting for one downlink CC linked to the uplink CC, indicated by the CI, among the plurality of downlink CCs; and

a triggering of CQI reporting for a first group of downlink CCs among the plurality of downlink CCs.

14. The method of claim 13, wherein:

if a value related to the CQI request is set to a first value, the CQI request indicates the triggering of CQI reporting for the one downlink CC, and

if the value related to the CQI request is set to a second value, the CQI request indicates the triggering of CQI reporting for the first group of downlink CCs among the plurality of downlink CCs.

15. The method of claim 14, wherein, if the value related to the CQI request is set to a third value, the CQI request indicates a triggering of CQI reporting for a second group of downlink CCs among the plurality of downlink CCs.

16. The method of claim 15, further comprising:

receiving information on the first group of downlink CCs and the second group of downlink CCs from the base station.

17. The method of claim 13, wherein a number of bits for the CQI request is two.

18. The method of claim 13, wherein the CQI reporting based on the CQI request corresponds to an aperiodic CQI.

19. The method of claim 13, wherein the CQI reporting for the one downlink CC is aperiodic CQI reporting, and when the CQI request indicates the triggering of the aperiodic CQI reporting for the one downlink CC, the one downlink CC is identified by a linkage with the uplink CC indicated by the CI.

20. An apparatus configured to transmit a channel quality indicator (CQI) in a wireless communication system, the apparatus comprising:

a radio frequency (RF) unit configured with a plurality of downlink component carriers (CCs) and configured to transmit and receive a radio signal; and

a processor configured to:

control the RF unit to receive control information via a physical downlink control channel (PDCCH) from a base station, the control information including an uplink allocation and a CQI request, the control information including a carrier indicator (CI) indicating an uplink CC in which the uplink allocation is scheduled, and

control the RF unit to transmit the CQI via a physical uplink shared channel (PUSCH) of the uplink CC to the base station, based on the CQI request and the uplink allocation,

wherein the CQI request indicates one of:

a triggering of CQI reporting for one downlink CC linked to the uplink CC, indicated by the CI, among the plurality of downlink CCs; and

a triggering of CQI reporting for a first group of downlink CCs among the plurality of downlink CCs.

21. The apparatus of claim 20, wherein:

if a value related to the CQI request is set to a first value, the CQI request indicates the triggering of CQI reporting for the one downlink CC, and

if the value related to the CQI request is set to a second value, the CQI request indicates the triggering of CQI reporting for the first group of downlink CCs among the plurality of downlink CCs.

22. The apparatus of claim 21, wherein, if the value related to the CQI request is set to a third value, the CQI request indicates a triggering of CQI reporting for a second group of downlink CCs among the plurality of downlink CCs.

23. The apparatus of claim 22, wherein the processor is further configured to:

receive information on the first group of downlink CCs and the second group of downlink CCs from the base station.

24. The apparatus of claim 20, wherein a number of bits for the CQI request is two.