Abstract: A method of communicating on at least one channel group of a communication system provides improved data transfer efficiencies over conventional systems by using discrete transfer rates. The channel group is includes at least one forward channel for channeling data transmitted from a central station to a plurality of terminals. At least one return channel is included for channeling transmissions by any of the plurality of terminals to the central station. Changes in the discrete data transfer rate are optionally accompanied by a change in a slot timing rate based on a frame transmission rate used over the forward channel. The method also allows the assignment of a predetermined number of return channel slots for a transmit frame for at least one combination of forward and return channels having prescribed forward and return data rates.