require intelligence and digital predistortion on the base station side before entering the bus a traditional kartesian feedback loop possesses no problem the purpose is to make the function of the transmitter foreseeable the transmission line is located between other parts of the baseband and the base station unit the only task of the transmission line is to carry forward the raw data from base station units the data is in a digital format and is down converted and decimated this arrangement is to simplify the connection between different parts of the baseband an optional feature for supporting some receiver algorithms e g irc interference reduction combining in diversity receiving and combining is to sent the data to the transmission line together with a clock signal indicating sampling interval in relation to transmission bus feedback loop can be taken into consideration in a function of adaptivity and intelligence the used transmission formats can be defined freely but should be kept simple no synchronisation clock is needed because tcu can synchronise itself to the received signal when most of the baseband functions are moved from base station units to the digital exchange no complicated interfaces between base station units and the digital exchange are needed this fact leads to many benefits from the system operation and maintenance point loads of the different sectors can be redivided flexible if loads increase suddenly in some sector simplified base station architecture in regard of base station and exchange interfaces no complex interface between the exchange and the base station.