Abstract: A first and a second communication controllers are connected to each other via a communication line, and each covering a plurality of terminals and assigning vacant channel in response to a communication demand for communication of the terminals. The first communication controller sets in advance attribute information necessary for communication of each of the plurality of terminals, makes the channel assignment according to the attribute information, generates ECC of the channel assignment information, and transmits the ECC to the second communication controller. The second communication controller sets in advance attribute information necessary for communication of each of the plurality of terminals, makes the channel assignment according to the attribute information, generates ECC of the channel assignment information, compares own ECC and the received ECC of the first communication controller and transmits the comparison result to the first communication controller.