支持智能天线的无线局域网优化MAC协议

Based on the characteristics of IEEE 802.11 WLAN, a medium access control protocol SADCF+ is proposed in this paper to support smart antennas. A smart antenna has omnidirectional and directional operation modes. In SADCF+, before sending any data frame, the station stimulates the corresponding node to transmit a training sequence by means of omnidirectional RTS/CTS handshake mechanism. Based on the training sequence, the directional beam can be formed by the smart antenna. Then the station can transmit and receive data frames in directional mode. Other nodes save the transmission time of the sender and the receiver in omnidirectional mode by using omnidirectional network allocation vectors, and multiplex channel when they transmit in directional mode. SADCF+ can support smart antennas effectively and provide high throughput by multiplexing channel. Moreover, in SADCF+, data frames are transmitted in bi-direction, from senders to receivers and from receivers to senders. Hence, SADCF+ is more suitable than DCF to transmit TCP traffic over WLAN. SADCF+ is compatible with IEEE 802.11.