A method for simultaneous communication with multiple communication devices in a wireless local area network, the method comprising: allocating, by a first communication device, respective sub-channels of an orthogonal frequency division multiplexing, OFDM, communication channel to two or more second communication devices (25-1, 25-2, 25-3) for simultaneous OFDM transmission to the two or more second communication devices, including allocating a first sub-channel to a first one of the two or more second communication devices and a second sub-channel to a second one of the two or more second communication devices; generating, by the first communication device, respective downlink OFDM data units (302-1, 302-2, 302-3) for the two or more second communication devices using the corresponding allocated sub-channels, wherein the downlink OFDM data units comprise synchronization frames (904; 1002) that include respective quality of service indicators based on a medium access procedure to facilitate simultaneous transmission from the two or more second communication devices to the first communication device, including at least first and second quality of service indicators that are different from each other and correspond to the first and second ones of the two or more second communication devices, respectively; transmitting, by the first communication device, the downlink OFDM data units to the two or more second communication devices using the corresponding allocated sub-channels; and receiving, at the first communication device, at least i) a first uplink OFDM data unit that comprises a first aggregate media access control protocol data unit, A-MPDU (908; 1006-4), transmitted by the first one of the two or more second communication devices in response to the corresponding downlink OFDM data unit and ii) a second uplink OFDM data unit that comprises a second A-MPDU, transmitted by the second one of the two or more second communication devices in response to the corresponding downlink OFDM data unit, wherein the first uplink OFDM data unit is transmitted from the first one of the two or more second communication devices via the first sub-channel allocated to the first one of the two or more second communication devices and the second uplink OFDM data unit is transmitted from the second one of the two or more second communication devices via the second sub-channel allocated to the second one of the two or more second communication devices; wherein each of the first A-MPDU and the second A-MPDU comprises two or more MPDUs having the corresponding quality of service indicator. allocating, by a first communication device, respective sub-channels of an orthogonal frequency division multiplexing, OFDM, communication channel to two or more second communication devices (25-1, 25-2, 25-3) for simultaneous OFDM transmission to the two or more second communication devices, including allocating a first sub-channel to a first one of the two or more second communication devices and a second sub-channel to a second one of the two or more second communication devices; generating, by the first communication device, respective downlink OFDM data units (302-1, 302-2, 302-3) for the two or more second communication devices using the corresponding allocated sub-channels, wherein the downlink OFDM data units comprise synchronization frames (904; 1002) that include respective quality of service indicators based on a medium access procedure to facilitate simultaneous transmission from the two or more second communication devices to the first communication device, including at least first and second quality of service indicators that are different from each other and correspond to the first and second ones of the two or more second communication devices, respectively; transmitting, by the first communication device, the downlink OFDM data units to the two or more second communication devices using the corresponding allocated sub-channels; and receiving, at the first communication device, at least i) a first uplink OFDM data unit that comprises a first aggregate media access control protocol data unit, A-MPDU (908; 1006-4), transmitted by the first one of the two or more second communication devices in response to the corresponding downlink OFDM data unit and ii) a second uplink OFDM data unit that comprises a second A-MPDU, transmitted by the second one of the two or more second communication devices in response to the corresponding downlink OFDM data unit, wherein the first uplink OFDM data unit is transmitted from the first one of the two or more second communication devices via the first sub-channel allocated to the first one of the two or more second communication devices and the second uplink OFDM data unit is transmitted from the second one of the two or more second communication devices via the second sub-channel allocated to the second one of the two or more second communication devices; wherein each of the first A-MPDU and the second A-MPDU comprises two or more MPDUs having the corresponding quality of service indicator.