A base station receives access opportunities and packet data over a common packet channel. The common packet channel is defined by a predetermined set of codes and has a plurality of access opportunities. Each access opportunity is defined by a time slot and a signature. A code selection controller selects a currently unused code based on a code associated with a received access opportunity, such that a code, if available, is selected in response to receiving a signature in one of the time slots. The access opportunity defined by the received signature and the one time slot. A transmitter transmits an identifier of the selected available code. The transmitter sends communications encoded with the selected code.