A CDMA radio wave signal is transmitted at a first place (a base station). A mobile unit receives the first CDMA radio wave signal and stores at least a portion of the data in the received signal and returns it to the base station by attaching the portion of the data to the second data to be transmitted through spectrum spreading, wherein the data rate of the attached data is higher than the second data. The base station detects an upward line transmission quality from the received second CDMA radio wave signal from the mobile unit, the downward line transmission quality is measured in the mobile station and the data of the downward line transmission quality is attached in place of forwarded data. When a downward line transmission quality is lower than a reference, the data is retransmitted from the base station and for a predetermined interval in this condition, transmission is stopped as transmission controlling. Corresponding base and mobile stations are also disclosed.