A first communication device generates a packet associated with acknowledgment of frames corresponding to multiple second communication devices. Generating the packet includes generating a frame that includes a field having respective acknowledgment information for the multiple second communication devices in respective subfields. The subfields have a plurality of different formats. The subfields are arranged within the field in groups of adjacent subfields such that each group includes only subfields of a same format and/or includes only subfields corresponding to second communication devices that have communicated to the first communication device a same set of supported formats of the subfields. The first communication device transmits the packet to the multiple second communication devices.