Method for transmitting control information in wireless communication system and apparatus therefor

1. A method of generating Acknowledgement/Negative Acknowledgement (ACK/NACK) information by a user equipment (UE) in a wireless communication system supporting carrier aggregation, the method comprising:

receiving, by the UE from a base station (BS), a plurality of codewords through a plurality of downlink carriers, each of the plurality of downlink carriers supporting one or more codewords according to a transmission mode, and the transmission mode being independently configured per each of the plurality of downlink carriers;

determining, by the UE, a total number of ACK/NACK bits; and

generating, by the UE, a sequence of the ACK/NACK bits according to the total number of the ACK/NACK bits,

wherein the UE determines the total number of ACK/NACK bits based on a total number of the plurality of downlink carriers and a type of each transmission mode independently configured per each of the plurality of downlink carriers.

2. The method of claim 1 , wherein in determining the total number of ACK/NACK bits, the UE determines a number of ACK/NACK bits allocated for a corresponding downlink carrier to be the same as a number of codewords supported by the corresponding downlink carrier.

3. The method of claim 2 , wherein when 2 ACK/NACK bits corresponding to 2 codewords are allocated for the corresponding downlink carrier and only one of the 2 codewords is received through the corresponding downlink carrier, the UE sets an ACK/NACK bit corresponding to the other one of the 2 codewords as a NACK value.

4. The method of claim 2 , wherein the UE determines the number of ACK/NACK bits allocated for the corresponding downlink carrier regardless of a number of codewords actually received through the corresponding downlink carrier.

5. The method of claim 1 , wherein the UE determines the total number of the ACK/NACK bits by accumulating a number of codewords supported by each of the plurality of downlink carriers.

6. The method of claim 1 , wherein in generating the sequence of the ACK/NACK bits, the UE concatenates the ACK/NACK bits based on a downlink carrier index.

7. The method of claim 6 , wherein the UE concatenates the ACK/NACK bits such that an ACK/NACK bit having a lower downlink carrier index is placed first in the sequence of the ACK/NACK bits.

8. The method of claim 7 , wherein when 2 ACK/NACK bits have a same downlink carrier index, the UE concatenates the ACK/NACK bits such that an ACK/NACK bit having a lower codeword index among the 2 ACK/NACK bits is placed first in the sequence of the ACK/NACK bits.

9. The method of claim 1 ,

wherein 1 ACK/NACK bit is allocated per each of the plurality of codewords received in the UE, and

wherein the determined total number of the ACK/NACK bits is greater than or equals to a number of the plurality of codewords received in the UE.

10. The method of claim 1 , wherein each of the plurality of downlink carriers supports 1-codeword transmission or 2-codeword transmission according to the type of the transmission mode.

11. The method of claim 1 , further comprising:

performing block coding and quadrature phase shift keying (QPSK) modulation for the sequence of the ACK/NACK bits.

12. The method of claim 1 , further comprising:

performing repetition coding for the sequence of the ACK/NACK bits.

13. The method of claim 1 , further comprising:

transmitting, by the UE to the BS, ACK/NACK information for the plurality of downlink carriers through a physical uplink control channel (PUCCH) of one uplink carrier based on the sequence of the ACK/NACK bits.

14. A user equipment (UE) for generating Acknowledgement/Negative Acknowledgement (ACK/NACK) information in a wireless communication system supporting carrier aggregation, the UE comprising:

a receiver to receive, from a base station (BS), a plurality of codewords through a plurality of downlink carriers, each of the plurality of downlink carriers supporting one or more codewords according to a transmission mode, and the transmission mode being independently configured per each of the plurality of downlink carriers; and

a processor to determine a total number of ACK/NACK bits and to generate a sequence of the ACK/NACK bits according to the total number of the ACK/NACK bits,

wherein the processor determines the total number of ACK/NACK bits based on a total number of the plurality of downlink carriers and a type of each transmission mode independently configured per each of the plurality of downlink carriers.

15. The UE of claim 14 , wherein in determining the total number of ACK/NACK bits, the processor determines a number of ACK/NACK bits allocated for a corresponding downlink carrier to be the same as a number of codewords supported by the corresponding downlink carrier.

16. The UE of claim 15 , wherein when 2 ACK/NACK bits corresponding to 2 codewords are allocated for the corresponding downlink carrier and only one of the 2 codewords is received through the corresponding downlink carrier, the processor sets an ACK/NACK bit corresponding to the other one of the 2 codewords as a NACK value.

17. The UE of claim 15 , wherein the processor determines the number of ACK/NACK bits allocated for the corresponding downlink carrier regardless of a number of codewords actually received through the corresponding downlink carrier.

18. The UE of claim 15 , wherein in generating the sequence of the ACK/NACK bits, the processor concatenates the ACK/NACK bits based on a downlink carrier index.

19. The UE of claim 18 , wherein the processor concatenates the ACK/NACK bits such that an ACK/NACK bit having a lower downlink carrier index is placed first in the sequence of the ACK/NACK bits.

20. The UE of claim 19 , wherein when 2 ACK/NACK bits have a same downlink carrier index, the processor concatenates the ACK/NACK bits such that an ACK/NACK bit having a lower codeword index among the 2 ACK/NACK bits is placed first in the sequence of the ACK/NACK bits.