Method and Apparatus for Transmitting Ack/Nack in a Wireless Communication System Based on Tdd

1. A method of transmitting positive-acknowledgement (ACK)/negative-acknowledgement (NACK) by a user equipment (UE) in a time division duplex (TDD)-based wireless communication system, the method comprising: receiving, by the UE from a base station (BS), M downlink subframes in each of a primary serving cell and a secondary serving cell, where M is an integer greater than two, and the M downlink subframes are associated with an uplink subframe n; and transmitting, by the UE to the BS in the uplink subframe n, an ACK/NACK response for the received M downlink subframes by using one resource selected from four candidate resources based on the received M downlink subframes, wherein, among the four candidate resources, a first resource and a second resource are associated with a physical downlink shared channel (PDSCH) received in the primary serving cell or a semi-persistent scheduling release physical downlink control channel (SPS release PDCCH) for releasing semi-persistent scheduling received in the primary serving cell, and a third resource and a fourth resource are associated with a PDSCH received in the secondary serving cell.

2. The method of claim 1 , wherein at least one downlink subframe among the M downlink subframes received in the primary serving cell comprises: a physical downlink control channel (PDCCH) in which a downlink grant is transmitted by the BS, and the PDSCH received in the primary serving cell corresponding to the PDCCH.

3. The method of claim 2 , wherein the downlink grant includes a downlink assignment index (DAI) indicating a cumulative number of PDCCHs with an assigned PDSCH transmission.

4. The method of claim 3 , wherein, in the M downlink subframes received in the primary serving cell: if a PDSCH indicated by a first PDCCH with a DAI value equal to 1 is received, then the first resource is determined based on a first control channel element (CCE) used in transmission of the first PDCCH, or if a first SPS release PDCCH with a DAI value equal to 1 is received, then the first resource is determined based on a first CCE used in transmission of the first SPS release PDCCH, or if a PDSCH indicated by a second PDCCH with a DAI value equal to 2 is received, then the second resource is determined based on a first CCE used in transmission of the second PDCCH, or if a second SPS release PDCCH with a DAI value equal to 2 is received, then the second resource is determined based on a first CCE used in transmission of the second SPS release PDCCH.

5. The method of claim 3 , wherein, in the M downlink subframes received in the primary serving cell: if an SPS PDSCH, which is a PDSCH having no corresponding PDCCH, is received, then the first resource among the four candidate resources has one value determined from four values that are configured by using a higher layer signal, and the determined one value is indicated by an uplink transmit power control field in a PDCCH indicating activation of semi-persistent scheduling.

6. The method of claim 5 , wherein, in the M downlink subframes received in the primary serving cell: if a PDSCH indicated by detecting a first PDCCH with a DAI value equal to 1 is received, then the second resource is determined based on a first CCE used in transmission of the first PDCCH or if a first SPS release PDCCH with a DAI value equal to 1 is received, then the second resource is determined based on a first CCE used in transmission of the first SPS release PDCCH.

7. The method of claim 3 , wherein if a PDSCH, indicated by a third PDCCH with a DAI value equal to 1 received in the M downlink subframes in the primary serving cell, is received in the M downlink subframes in the secondary serving cell, then the third resource is determined based on a first CCE used in transmission of the third PDCCH, or if a PDSCH, indicated by a fourth PDCCH with a DAI value equal to 2 received in the M downlink subframes in the primary serving cell, is received in the M downlink subframes in the secondary serving cell, then the fourth resource is determined based on a first CCE used in transmission of the fourth PDCCH.

8. The method of claim 3 , wherein if at least one PDCCH is received in the M downlink subframes received in the secondary serving cell, and a PDSCH indicated by the at least one PDCCH is received in the secondary serving cell: then the third resource and the fourth resource are have values determined by a higher layer signal, and the third and fourth resources are indicated by an uplink transmission power control (TPC) field included in the at least one PDCCH.

9. A user equipment (UE) configured to transmit positive-acknowledgement (ACK)/negative-acknowledgement (NACK) in a time division duplex (TDD)-based wireless communication system, the UE comprising: a radio frequency (RF) unit; and a processor operatively connected to the RF unit and configured to: receive, from a base station (BS), M downlink subframes in each of a primary serving cell and a secondary serving cell, where M is an integer greater than two, and the M downlink subframes are associated with an uplink subframe n; and transmit, to the BS in the uplink subframe n, an ACK/NACK response for the received M downlink subframes by using one resource selected from four candidate resources based on the received M downlink subframes, wherein, among the four candidate resources, a first resource and a second resource are associated with a physical downlink shared channel (PDSCH) received in the primary serving cell or a semi-persistent scheduling release physical downlink control channel (SPS release PDCCH) for releasing semi-persistent scheduling received in the primary serving cell, and a third resource and a fourth resource are associated with a PDSCH received in the secondary serving cell.

10. The UE of claim 9 , wherein at least one downlink subframe among the M downlink subframes received in the primary serving cell comprises: a physical downlink control channel (PDCCH) in which a downlink grant is transmitted by the BS, and the PDSCH received in the primary serving cell corresponding to the PDCCH.

11. The UE of claim 10 , wherein the downlink grant includes a downlink assignment index (DAI) indicating a cumulative number of PDCCHs with an assigned PDSCH transmission.

12. The UE of claim 11 , wherein, in the M downlink subframes received in the primary serving cell: if a PDSCH indicated by a first PDCCH with a DAI value equal to 1 is received, then the first resource is determined based on a first control channel element (CCE) used in transmission of the first PDCCH, or if a first SPS release PDCCH with a DAI value equal to 1 is received, then the first resource is determined based on a first CCE used in transmission of the first SPS release PDCCH, or if a PDSCH indicated by a second PDCCH with a DAI value equal to 2 is received, then the second resource is determined based on a first CCE used in transmission of the second PDCCH, or if a second SPS release PDCCH with a DAI value equal to 2 is received, then the second resource is determined based on a first CCE used in transmission of the second SPS release PDCCH.

13. The UE of claim 11 , wherein, in the M downlink subframes received in the primary serving cell: if an SPS PDSCH, which is a PDSCH having no corresponding PDCCH, is received, then the first resource among the four candidate resources has one value determined from four values that are configured by using a higher layer signal, and the determined one value is indicated by an uplink transmit power control field in a PDCCH indicating activation of semi-persistent scheduling.

14. The UE of claim 13 , wherein, in the M downlink subframes received in the primary serving cell: if a PDSCH indicated by detecting a first PDCCH with a DAI value equal to 1 is received, then the second resource is determined based on a first CCE used in transmission of the first PDCCH or if a first SPS release PDCCH with a DAI value equal to 1 is received, then the second resource is determined based on a first CCE used in transmission of the first SPS release PDCCH.

15. The UE of claim 11 , wherein if a PDSCH, indicated by a third PDCCH with a DAI value equal to 1 received in the M downlink subframes in the primary serving cell, is received in the M downlink subframes in the secondary serving cell, then the third resource is determined based on a first CCE used in transmission of the third PDCCH, or if a PDSCH, indicated by a fourth PDCCH with a DAI value equal to 2 received in the M downlink subframes in the primary serving cell, is received in the M downlink subframes in the secondary serving cell, then the fourth resource is determined based on a first CCE used in transmission of the fourth PDCCH.

16. The UE of claim 11 , wherein if at least one PDCCH is received in the M downlink subframes received in the secondary serving cell, and a PDSCH indicated by the at least one PDCCH is received in the secondary serving cell: then the third resource and the fourth resource are have values determined by a higher layer signal, and the third and fourth resources are indicated by an uplink transmission power control (TPC) field included in the at least one PDCCH.