A multiple mode data communication system and method provides the flexibility to schedule wireless unit transmissions and/or allow the wireless unit to transmit autonomously. In certain embodiments, the wireless units can transmit autonomously and/or use scheduling depending on the data rate, the length of the data packet or the type of data. For example, the wireless units can transmit autonomously at lower data rates and use scheduling at higher data rates. Thus, the multiple mode system enables wireless unit transmissions to be scheduled and/or be transmit autonomously, and wireless units can simultaneously operate in different scheduling and/or autonomous modes. Depending on the embodiment, the system can provide even greater flexibility in operation by permitting wireless units to be scheduled by a single base station, scheduled by a multiplicity of base stations simultaneously or otherwise, via coordination between base stations, scheduled by a multiplicity of base stations in an uncoordinated and asynchronous manner, allowed to transmit autonomously, and/or allowed to transmit autonomously under base station supervision (i.e. rate control/adjustment by the base station). Additionally, a forward and/or reverse link control channel structure is provided which can be used to implement the multiple mode data communication system and/or support various features enabling increased throughput over a shared data channel in a wireless communications system.