Abstract: A method of an uplink scheduler for a base station in a wireless communication system is provided. The wireless communication system performs uplink wireless access for a best effort service, based on random access. The uplink scheduler of the base station transmits downlink traffic data to a user terminal, and estimates uplink traffic data generated from the user terminal based on the downlink traffic data. In addition, the uplink scheduler allocates resources for the estimated uplink traffic data to the user terminal, and receives the uplink traffic data transmitted from the user terminal by using the resources allocated to the user terminal.