Uplink Multi-User-MIMO without Client Assistance

An apparatus comprising:

• a plurality of transmit upconverters each coupled to a corresponding one of a plurality of antennas;
• a plurality of receive downconverters each coupled to a corresponding one of the plurality of antennas;
• a signal processor coupled to the plurality of transmit upconverters and the plurality of receive downconverters, wherein the signal processor is configured to:
• cause a downlink multi-user multiple-input multiple-output (MIMO) transmission to be sent to a plurality of client devices via the plurality of transmit upconverters, the transmission configured to solicit acknowledgments from two or more of the plurality of client devices;
• cause the plurality of receive downconverters to receive the acknowledgments from the two or more of the plurality of client devices;
• perform uplink multi-user MIMO processing of the acknowledgments from the two or more of the plurality of client devices to recover the acknowledgments respectively from each of the two or more of the plurality of client device,
• select a single client device of the plurality of client devices;
• cause a single-user downlink transmission to be sent via at least one of the plurality of transmit upconverters to further solicit an acknowledgment from the single client device;
• and
• cause at least one of the plurality of receive downconverters to receive the acknowledgment from the single client device.

A system comprising:

• at least a first wireless access point;
• a plurality of client devices;
• wherein the first wireless access point is configured to:
• send a downlink multi-user multiple-input multiple-output (MIMO) transmission to a plurality of client devices, the transmission configured to solicit acknowledgments from two or more of the plurality of client devices;
• receive the acknowledgments from the two or more of the plurality of client devices;
• and
• perform uplink multi-user MIMO processing of the acknowledgments from the two or more of the plurality of client devices to recover the acknowledgments respectively from each of the two or more of the plurality of client devices,
• wherein one or more of:
• the downlink multi-user MIMO transmission includes a preamble that does not support user separation;
• a Media Access Control (MAC) protocol between the first wireless access point and the plurality of client devices is used such that two or more of the plurality of client devices are unaware that each may be simultaneously transmitting an acknowledgment but which acknowledgments from the two or more of the plurality of client devices are aligned within a cyclic extension interval;
• the plurality of client devices do not support carrier frequency alignment to a reference;
• and
• the first wireless access point is operating, with respect to the two or more of the plurality of client devices, at a range such that per-client ranging is not required and the alignment of the acknowledgments received at the first wireless access point is preserved.