Method for transmitting control information and apparatus therefor

1. A method for a user equipment (UE) transmitting uplink control information in a wireless communication system supporting carrier aggregation, the method comprising:

receiving one or more downlink signals each corresponding to a physical downlink control channel (PDCCH) indicating downlink semi-persistent scheduling (SPS) release or a physical downlink shared channel (PDSCH) in a plurality of downlink subframes according to an uplink (UL)-downlink (DL) configuration for time division duplex (TDD);

receiving a PDCCH with a downlink control information (DCI) format for UL scheduling, wherein the DCI format for UL scheduling includes a downlink assignment index (DAI) field; and

transmitting acknowledgement (ACK)/negative acknowledgement (NACK) information for the one or more downlink signals through a physical uplink shared channel (PUSCH) based on the received PDCCH with the DCI format for UL scheduling,

wherein a number of bits of the ACK/NACK information is determined using a formula:

V DAI UL +4┌(U max −V DAI UL )/4┐,

where V DAI UL denotes an integer determined by the DAI field in a range of 1 to 4, U max denotes a maximum value among values each indicating a number of received downlink signals per each component carrier in the plurality of downlink subframes, and ┌ ┐ represents a ceiling function.

2. The method according to claim 1 , wherein the ACK/NACK information includes ACK/NACK information on one or more component carriers and the number of bits of ACK/NACK information for a c-th component carrier is:

i) (V DAI UL +4┌(U max −V DAI UL )/4┐) when a transmission mode supporting transmission of a single transport block is configured for the c-th component carrier or bundling is applied for the c-th component carrier; and

ii) 2×(V DAI UL +4┌(U max −V DAI UL )/4┐) when a transmission mode supporting transmission of two transport blocks is configured for the c-th component carrier and bundling is not applied thereto.

3. The method according to claim 1 , wherein the DAI field is represented by 2 bits.

4. The method according to claim 1 , wherein the formula V DAI UL +4┌(U max −V DAI UL )/4┐corresponds to a number of downlink subframes requiring feedback of ACK/NACK information for a corresponding component carrier.

5. The method according to claim 1 , wherein the UL-DL configuration is a TDD subframe configuration following Table A:

TABLE A

DL to UL switch-

subframe number

point periodicity

0

1

2

3

4

5

6

7

8

9

10 ms

D

S

U

D

D

D

D

D

D

D

wherein D denotes a downlink subframe, U denotes an uplink subframe and S denotes a special subframe including a Downlink Pilot TimeSlot (DwPTS), a Guard Period (GP), and an Uplink Pilot TimeSlot (UpPTS).

6. A communication device configured to transmit uplink control information in a wireless communication system supporting carrier aggregation and operating in time division duplex (TDD), the communication device comprising:

a radio frequency (RF) unit; and

a processor coupled to the RF unit,

wherein the processor is configured to receive one or more downlink signals each corresponding to a physical downlink control channel (PDCCH) indicating downlink semi-persistent scheduling (SPS) release or a physical downlink shared channel (PDSCH) in a plurality of downlink subframes according to an uplink (UL)-downlink (DL) configuration, and receive a PDCCH with a downlink control information (DCI) format for UL scheduling, wherein the DCI format for UL scheduling includes a downlink assignment index (DAI) field determining a value V DAI UL , to transmit acknowledgement (ACK)/negative acknowledgement (NACK) information for the one or more downlink signals through a physical uplink shared channel (PUSCH) based on the received PDCCH with the DCI format for UL scheduling,

wherein a number of bits of the ACK/NACK information is determined using a formula:

V DAI UL +4┌(U max −V DAI UL )/4┐,

where V DAI UL is an integer in a range of 1 to 4, U max denotes a maximum value among values each indicating a number of received downlink signals per each component carrier in the plurality of downlink subframes and ┌ ┐ resents a ceiling function.

7. The communication device according to claim 6 , wherein the ACK/NACK information includes ACK/NACK information on one or more component carriers and the number of bits of ACK/NACK information for a c-th component carrier is:

i) (V DAI UL +4┌(U max −V DAI UL )/4┐) when a transmission mode supporting transmission of a single transport block is configured for the c-th component carrier or bundling is applied for the c-th component carrier; and

ii) 2×(V DAI UL +4┌(U max −V DAI UL )/4┐) when a transmission mode supporting transmission of two transport blocks is configured for the c-th component carrier and bundling is not applied thereto.

8. The communication device according to claim 6 , wherein the DAI field is represented by 2 bits.

9. The communication device according to claim 6 , wherein the formula V DAI UL +4┌(U max −V DAI UL )/4┐ corresponds to a number of downlink subframes requiring feedback of ACK/NACK information for a corresponding component carrier.

10. The communication device according to claim 6 , wherein the UL-DL configuration is a TDD subframe configuration following Table A:

TABLE A

DL to UL switch-

subframe number

point periodicity

0

1

2

3

4

5

6

7

8

9

10 ms

D

S

U

D

D

D

D

D

D

D

wherein D denotes a downlink subframe, U denotes an uplink subframe and S denotes a special subframe including a Downlink Pilot TimeSlot (DwPTS), a Guard Period (GP), and a Uplink Pilot TimeSlot (UpPTS).