A method of improved allocation of uplink resources in an OFDMA network is proposed. A wireless communications station (an AP) reserves both dedicated resource and contention resource for uplink OFDMA operation for a list of communications devices (STAs). The AP can switch between random access operation and non-random access operation without the need for any special protection mechanisms. In the event of an increase in uplink OFDMA frame collisions the AP can switch from random operation to non-random operation to reduce the number of collisions. In the event of a decrease in uplink OFDMA frame collisions the AP can switch from non-random operation to random operation to reduce required AP processing. The AP can also dynamically control a STA access probability to reduce the number of collisions by reducing the number of uplink OFDMA frames each STA transmits.