The apparatus has a Transmission/reception amplifying unit (2) for the amplification of CDMA signals from and to a mobile station. A base band-spread transmission signal which is passed through the amplifying unit is then D-A converted to analogue by a radio unit (3) and then quadrature modulated, quasi-synchronously detecting a received signal which is then A-D converted to a digital signal. The system also has a base band signal processing unit (4), connected to the radio unit which subjects both the transmission and received signals to the base band signal processing, a transmission channel interface (6) which is connected to the base band signal processing unit which serves as an interface with an external line, and a control unit which controls radio circuits and their setting/resetting. Communication with an external line occurs using ATM cells. The communication with the mobile station by using CDMA signals is effected by mapping a series of logic channels on a series of physical channels. The band of the CDMA signals is spread with two short and long spread-series codes.