(Based on the full consideration of the characteristics of IEEE802.11 wireless local area network, this article proposes a medium access control protocol that supports smart antennas: SADCF . The smart antenna includes both omnidirectional and directional office modes. SADCF uses the omnidirectional RTS/CTS handshake mechanism to reserve the channel as short as possible before sending the data frame, and guide the sending or receiving station to send the practice sequence.)