In this paper, we propose a time-frequency resource allocation scheme for OFDMA based system in WiMAX access networks. We utilize a user-based scheduling scheme to reduce complexity. The user with the highest priory is scheduled first on its best subchannel. The resource allocation is performed to guarantee the QoS requirements of various traffic first and to improve throughput next. The simulation results show that the proposed allocation scheme can provide diverse QoS guarantees and use resources efficiently.