A communication system including a mobile station (202, 322) sending a plurality of uplink radio link control data blocks (328, 332, 336, 340) to a base station (208, 320) in an uplink temporary block flow (248), and receiving a plurality of downlink radio link control data blocks (326, 330, 334, 338, 342) from the base station in a downlink temporary block flow (225). The communication system includes a protocol control unit (214) within the base station, having a base station medium access control layer (213) that sends an identifier during setup of the downlink temporary block flow (224), and sends an uplink state flag indicating channel availability in a first one of the plurality of downlink radio link control data blocks (326). A GPRS/EDGE subsystem (210) is located within the mobile station, having a mobile station medium access control layer (211) that receives the identifier and the uplink state flag, and sends uplink data in a first one of the plurality of uplink radio link control data blocks (32) to the base station in response to the uplink state flag indicating channel availability. The base station medium access control layer sends a directed acknowledgement in a subsequent one of the plurality of downlink radio link control data blocks (330) in response to receipt of the uplink data from the mobile station, and the mobile station sends uplink data in a second one of the plurality of uplink radio link control data blocks (332) in response to the directed acknowledgement.