A user equipment comprising: a transmitter configured to transmit hybrid automatic repeat request-acknowledgement, HARQ-ACK, bits in a subframe n, and a receiver configured to detect downlink control information, DCI, format 0 or 4 corresponding to a physical uplink shared channel on a serving cell, wherein the number of the HARQ-ACK bits is determined based on a value of W DAI UL, in a case that the user equipment is configured with more than one serving cell, frame structure types of at least two configured serving cells included in the more than one serving cell are different, and a primary cell is frame structure type 2, wherein frame structure type 2 is defined as Time Division Duplex, TDD; for the serving cell with frame structure type other than the frame structure type 2, the value of the W DAI UL is determined by a downlink assignment index, DAI, in a subframe n-4, for the serving cell with the frame structure type 2, the value of the W DAI UL is determined by the DAI in a subframe n-k', the k' being defined on the basis of the n and an uplink-reference uplink/downlink configuration for the serving cell with the frame structure type 2, the DAI is included in the DCI format 0 or 4, characterized in that transmission timing of the HARQ-ACK bits is determined based on one of downlink association sets, and the downlink association sets are individually configured for (i) a case in which self scheduling is configured for the serving cell with frame structure type other than the frame structure type 2 and a frame structure of a primary cell is the frame structure type 2, and (ii) a case in which cross carrier scheduling is configured for the serving cell with frame structure type other than the frame structure type 2 and a frame structure of a primary cell is the frame structure type 2. a transmitter configured to transmit hybrid automatic repeat request-acknowledgement, HARQ-ACK, bits in a subframe n, and a receiver configured to detect downlink control information, DCI, format 0 or 4 corresponding to a physical uplink shared channel on a serving cell, wherein the number of the HARQ-ACK bits is determined based on a value of W DAI UL, in a case that the user equipment is configured with more than one serving cell, frame structure types of at least two configured serving cells included in the more than one serving cell are different, and a primary cell is frame structure type 2, wherein frame structure type 2 is defined as Time Division Duplex, TDD; for the serving cell with frame structure type other than the frame structure type 2, the value of the W DAI UL is determined by a downlink assignment index, DAI, in a subframe n-4, for the serving cell with the frame structure type 2, the value of the W DAI UL is determined by the DAI in a subframe n-k', the k' being defined on the basis of the n and an uplink-reference uplink/downlink configuration for the serving cell with the frame structure type 2, the DAI is included in the DCI format 0 or 4, characterized in that transmission timing of the HARQ-ACK bits is determined based on one of downlink association sets, and the downlink association sets are individually configured for (i) a case in which self scheduling is configured for the serving cell with frame structure type other than the frame structure type 2 and a frame structure of a primary cell is the frame structure type 2, and (ii) a case in which cross carrier scheduling is configured for the serving cell with frame structure type other than the frame structure type 2 and a frame structure of a primary cell is the frame structure type 2.