To enhance communication quality, to increase a transmission efficiency between a base station and a base station controller and to decrease a capacity of a frame buffer for selection and synthesis.

A plurality of base stations 102-104 assemble a frame signal resulting from adding radio quality information and time information at reception to a reception signal by a mobile station 101, after receiving the frame signal by a base station controller 105, a time information separate means 115 separates the time information, a 1st frame read means 119 reads a frame signal stored in a storage area of a frame buffer 118 corresponding to the separated time information, a selection synthesis means 116 selects the read frame signal or the frame signal from which the time information is separated which has higher quality, a frame write means 117 stores the selected frame signal in the storage area of the buffer 118 corresponding to the separated time information and a 2nd frame read means 120 reads the stored frame signal and outputs it to a communication network.