A method is provided for controlling uplink data traffic in a wireless communication system. If Internet Protocol (IP) packets are received from a higher layer, one or more medium access control service data units (MAC SDUs) are generated in units of sub-blocks. A modified packing sub-header (PSH) used for distinguishing between the MAC SDUs is added to the generated MAC SDUs. MAC SDUs having the same connection identifier (CID) among the modified PSH-added MAC SDUs are grouped. A modified MAC header (MH) used for distinguishing between the MAC SDU groups is added to generate one or more tunnel messages, and the generated tunnel messages are grouped. A tunnel frame header used for distinguishing between the tunnel messages to generate a tunnel frame is added thereto. The generated tunnel frame is transmitted to a base station.