In 802.11ac networks, a communication is performed over a composite channel made of one primary and one or more secondary sub-channels. To provide feedback on reception quality over secondary sub-channels without overhead, a receiving node may determine a channel quality 923 for the, or each, secondary sub-channels and send to a source node in response to received data frames, a duplicated ACK frame only on the secondary sub-channels having a high determined channel quality, for instance above a quality threshold 924. Lack of a duplicated ACK frame on a secondary sub-channel is detected by the source node to infer that this sub-channel has unsatisfactory reception quality. The source node may thus modify the composite channel for future transmission, by removing, from the composite channel, such unsatisfactory quality sub-channel(s) on which no duplicated acknowledgment frame is received. The ACK sent on the primary channel and the one or more duplicated ACKs sent on the secondary sub-channel(s) are sent subs
