A multiple access communication system performs the communication between plural communicating units using plural communicating channels and a common signalling channel for establishing and releasing the communicating channels. The communication system comprises the steps of allocating at least one carrier frequency to the common signalling channel; allocating the carrier frequencies, which are different from the carrier frequency alloted to the common signalling channel, to the communicating channels; forming a time frame composed of first and second time slots by the common signalling channel and communicating channel, respectively; and allocating the first time slot to at least the common signalling channel and the second time slot to the communicating channel.A multiple access communication system performs the communication between plural communicating units by selectively allocating plural carrier frequencies, which are different from the common signalling channel carrier frequency, to the plural communicating channels, and using a common signalling channel for establishing and releasing the communicating channels. The commnication system comprises the steps of constituting a time frame of communicating channel by at least one packet; selecting transmission parameters of the communicating channel including at least transmission speed, packet length and packet position from plural transmission parameters prepared in advance; and setting the selected transmission parameters through the common signalling channel.