Patent ID: 8891416

Claim:
A method of transmitting a positive-acknowledgement (ACK)/negative-acknowledgement (NACK) in a wireless communication system based on time division duplex in which M, M>1, downlink subframes are associated with an uplink subframe, performed by a user equipment, the method comprising: receiving a first downlink transport block on a first physical downlink shared channel (PDSCH) in one of the M downlink subframes on a primary cell; receiving a second downlink transport block on a second PDSCH in one of the M downlink subframes on the primary cell; determining whether a first physical downlink control channel (PDCCH) corresponding to the first PDSCH is received on the primary cell; determining whether a second PDCCH, which corresponds to the second PDSCH and includes a downlink assignment index (DAI), is received on the primary cell, the DAI indicating an accumulative number of PDCCH with assigned PDSCH transmission; if the first PDCCH is not received on the primary cell and the second PDCCH is received on the primary cell, determining a 2 bit ACK/NACK for the first downlink transport block and the second downlink transport block, and further determining a resource index from a plurality of resource indexes; and transmitting the 2 bit ACK/NACK on an uplink control channel configured by the determined resource index.