Techniques and apparatus for hybrid automatic retransmission request (HARQ) acknowledgement (ACK) bundling in half duplex frequency division duplexing (HD-FDD) systems are provided. One technique includes determining ACK parameter(s) to be used for acknowledging a bundled transmission that includes instance(s) of a channel across subframe(s). An indication of the ACK parameter(s) is signaled to a user equipment (UE). The ACK parameter(s) include a first ACK parameter that conveys a size of the bundled transmission and a second ACK parameter that conveys an amount of time for the UE to delay acknowledging a data transmission in an instance of the channel after receiving the data transmission. The UE may acknowledge the bundled transmission in accordance with the ACK parameter(s).