A method for an uplink transmission comprising: receiving, by an user equipment, UE, first downlink data from a first cell via a first physical downlink shared channel, PDSCH, in a first subframe; receiving, by the UE, second downlink data from a second cell via a second PDSCH in the first subframe; transmitting, by the UE and to the first cell, in a second subframe, first uplink data by using a first resource in response to the first downlink data; and transmitting, by the UE and to the second cell, in the second subframe, second uplink data by using a second resource in response to the second downlink data, wherein the first resource for the first cell is determined based on a first replacement cell identifier instead of a physical cell identifier of the first cell and the second resource for the second cell is determined based on a second replacement cell identifier instead of a physical cell identifier of the second cell, wherein the first replacement cell identifier of the first cell and the second replacement cell identifier of the second cell are configured by a higher layer using radio resource control, RRC, connection, wherein the first uplink data includes first acknowledgement/non-acknowledgement, ACK/NACK, bits in response to the first downlink data, wherein the second uplink data includes second ACK/NACK bits in response to the second downlink data, wherein a number of the first ACK/NACK bits included in the first uplink data is determined based on a downlink transmission mode of the first cell, and wherein a number of the second ACK/NACK bits included in the second uplink data is determined based on a downlink transmission mode of the second cell. receiving, by an user equipment, UE, first downlink data from a first cell via a first physical downlink shared channel, PDSCH, in a first subframe; receiving, by the UE, second downlink data from a second cell via a second PDSCH in the first subframe; transmitting, by the UE and to the first cell, in a second subframe, first uplink data by using a first resource in response to the first downlink data; and transmitting, by the UE and to the second cell, in the second subframe, second uplink data by using a second resource in response to the second downlink data, wherein the first resource for the first cell is determined based on a first replacement cell identifier instead of a physical cell identifier of the first cell and the second resource for the second cell is determined based on a second replacement cell identifier instead of a physical cell identifier of the second cell, wherein the first replacement cell identifier of the first cell and the second replacement cell identifier of the second cell are configured by a higher layer using radio resource control, RRC, connection, wherein the first uplink data includes first acknowledgement/non-acknowledgement, ACK/NACK, bits in response to the first downlink data, wherein the second uplink data includes second ACK/NACK bits in response to the second downlink data, wherein a number of the first ACK/NACK bits included in the first uplink data is determined based on a downlink transmission mode of the first cell, and wherein a number of the second ACK/NACK bits included in the second uplink data is determined based on a downlink transmission mode of the second cell.