A base station for use in wireless network that communicating with subscriber stations according to a multicarrier protocol. The base station receives uplink signals transmitted by the subscriber stations and measures the channel quality of each uplink acknowledgment signal channel. The base station transmits to a first subscriber station a control message that assigns the first subscriber station to transmit a first acknowledgment signal in a first selected uplink acknowledgment signal channel. The base station selects the first selected uplink acknowledgment signal channel based on a first measured channel quality associated with the first selected uplink acknowledgment signal channel.