Embodiments of the disclosure generally relate to feedback of a HARQ acknowledgement. A network device transmits, to a terminal device, a first trigger indicating a feedback mode of a HARQ acknowledgement. The feedback mode is selected from at least one of: a trigger mode, a timing mode, and a mixed mode. In response to successful access to an unsilenced band allocated to the HARQ acknowledgement, the network device transmits, to the terminal device, a second trigger indicating at least one target terminal device that is to feedback the HARQ acknowledgement based on the feedback mode indicated by the first trigger.