A method and apparatus for providing acknowledgment information for radio communication devices in a wireless communication system. A base station receives a plurality of units of data each respectively transmitted by one of a plurality of radio communication devices on one of a plurality of predetermined communication slot positions of a first channel. The base station, in response to receiving the data messages, sends a control message on a communication slot position of a second channel. The control message includes acknowledgment information having a plurality of positional acknowledgment indicators. Each radio communication device receives the control message and uses acknowledgment position mapping information to identify one or more positions within the plurality of positional acknowledgment indicators that contains an acknowledgment to the respective units of data it transmitted on the corresponding predetermined communication slot positions of the first channel.