To attain the control of collisions among the transmission cells sent from plural base stations and to secure the impartial accesses to a network for the base stations by monitoring the cells on an asynchronous transmission mode circuit to decide whether the cells can be sent or not and then sending the cells to the asynchronous transmission mode circuit based on the decision result.

The base stations 1 to 3 having the ATM (asynchronous transmission mode) circuit interfaces are connected to an ATM circuit 101. The monitor parts 8 and 11 of stations 2 and 3 monitor the empty cells which are sent to the circuit 101 by a cell sending part 4 of the station (master base station) 1. Then the sell sending arbitration parts 9 and 12 decide whether the cells can be sent to the circuit 101 based on the monitoring results of the parts 8 and 11. The cell sending parts 7 and 10 send the cells to the circuit 101 based on the decision results of the parts 9 and 12. In such a constitution, the conflicts and collisions of cells sent from plural base stations can be arbitrated by means of a single ATM circuit.