An access network device, comprising: a sending module, configured to: send downlink scheduling information of a downlink subframe F(i, j) to a terminal, and send, to the terminal in the downlink subframe F(i, j), downlink data scheduled by the downlink scheduling information, wherein the downlink subframe F(i, j) is a subframe in a set M of preconfigured downlink subframes corresponding to an uplink subframe; wherein F(i, j) represents a downlink subframe j on a carrier i configured for the terminal, i ∈ C, C is a set of all carriers configured for the terminal for downlink data transmission, j ∈ K, and K is a set of downlink subframes corresponding to the uplink subframe; and the set M of preconfigured downlink subframes is divided into N subsets of preconfigured downlink subframes, N is an integer greater than or equal to 2, a bit quantity of a HARQ-ACK that needs to be fed back for each downlink subframe in a subset of preconfigured downlink subframes is a predetermined value, and bit quantities of hybrid automatic repeat request-acknowledgements HARQ-ACKs that need to be fed back for any downlink subframes in different subsets of preconfigured downlink subframes are different; a receiving module, configured to receive uplink control information that is sent by the terminal in the first subframe and that is used for feeding back a receiving status of the downlink data scheduled by the downlink scheduling information; and a processing module, configured to obtain a HARQ-ACK codebook by decoding the uplink control information, wherein the obtained HARQ-ACK codebook comprises at least one sub-codebook, the at least one sub-codebook is in one-to-one correspondence with at least one subset of preconfigured downlink subframes, the at least one subset of preconfigured downlink subframes is at least one of the N subsets of preconfigured downlink subframes, and the at least one subset of preconfigured downlink subframes is a subset comprising downlink subframes in which the downlink data scheduled by the downlink scheduling information is sent. a sending module, configured to: send downlink scheduling information of a downlink subframe F(i, j) to a terminal, and send, to the terminal in the downlink subframe F(i, j), downlink data scheduled by the downlink scheduling information, wherein the downlink subframe F(i, j) is a subframe in a set M of preconfigured downlink subframes corresponding to an uplink subframe; wherein F(i, j) represents a downlink subframe j on a carrier i configured for the terminal, i ∈ C, C is a set of all carriers configured for the terminal for downlink data transmission, j ∈ K, and K is a set of downlink subframes corresponding to the uplink subframe; and the set M of preconfigured downlink subframes is divided into N subsets of preconfigured downlink subframes, N is an integer greater than or equal to 2, a bit quantity of a HARQ-ACK that needs to be fed back for each downlink subframe in a subset of preconfigured downlink subframes is a predetermined value, and bit quantities of hybrid automatic repeat request-acknowledgements HARQ-ACKs that need to be fed back for any downlink subframes in different subsets of preconfigured downlink subframes are different; a receiving module, configured to receive uplink control information that is sent by the terminal in the first subframe and that is used for feeding back a receiving status of the downlink data scheduled by the downlink scheduling information; and a processing module, configured to obtain a HARQ-ACK codebook by decoding the uplink control information, wherein the obtained HARQ-ACK codebook comprises at least one sub-codebook, the at least one sub-codebook is in one-to-one correspondence with at least one subset of preconfigured downlink subframes, the at least one subset of preconfigured downlink subframes is at least one of the N subsets of preconfigured downlink subframes, and the at least one subset of preconfigured downlink subframes is a subset comprising downlink subframes in which the downlink data scheduled by the downlink scheduling information is sent.