The total amount of power for communications transmitted over channels susceptible to quality fluctuation is decreased to reduce interference with other communications and increase the system's overall capacity. When channel-encoded data is to be transmitted, the quality of a transmission channel is judged. The data is transmitted when the judged quality is higher than predefined. However, if the quality is lower than predefined, the data transmission to a wireless section is suppressed to avoid a signal transmission that cannot effectively be used at a receiving station, decrease the average transmission power, and reduce interference with other communications. Even if the channel quality is lower than predefined at the time of assigning a code word created by channel encoding, the same code word assignment operation as for a transmission portion is performed with respect to a no-transmission portion that a transmitting station does not send to a wireless section.