An AP allows a CTS generator provided within a control unit to generate a self-destined, e.g., IEEE802.11b standard-based CTS signal containing a duration time corresponding to each standard. Then, the AP notifies to each STA operated based on the 11b standard in a basic service set, that it is being ready for transmission due to the transmission of the CTS signal, thereby to prohibit the operation of the corresponding STA. Further, the AP transmits a beacon based on an IEEE802.11g standard to thereby set a condition based on this standard and is caused to perform transmission/reception to and from the corresponding STA alone over the duration time indicated by the 11b standard. In a reverse case, the AP transmits a CTS signal containing a self-destined duration time under the IEEE802.11g standard to prohibit the operation of the corresponding STA based on the 11g standard. Further, the AP transmits a beacon based on the 11b standard to thereby set a condition based on this standard and is caused to perform transmission/reception to and from the corresponding station alone over the duration time indicated by the 11g standard.
