A method is provided in which a first wireless access point selects two or more of a plurality of client devices based on similarity of receive signal strength and carrier frequency offset with respect to the first wireless access point, and sends a downlink multi-user multiple-input multiple-output (MIMO) transmission to the two or more client devices. The downlink multi-user MIMO transmission is configured to solicit acknowledgments from the two or more client devices. The acknowledgments are received at a plurality of antennas of the first wireless access point from the two or more client devices. Uplink multi-user MIMO processing of the acknowledgments is performed from the two or more of the plurality of client devices to recover the acknowledgments respectively from each of the two or more client devices.