Wireless communication in a wireless network comprises obtaining a transmission opportunity period (TXOP) for communicating with an access point (AP) over a wireless communication channel. An announcement is sent to the AP to share the transmission opportunity period among wireless stations, as a multi-user transmission opportunity period for simultaneously transmitting data from said wireless stations to the AP on multiple uplink (UL) spatial streams over the wireless channel. Correctly received UL frames received by the AP are acknowledged. Error recovery and backoff processing are performed upon loss of communication information based on frame type.