request to send/clear to send (802.11) (RTS/CTS)
Request to Send/Clear to Send(RTS/ CTS) is a mechanism for accessing the medium and distributing the NAV vector, Network Allocation Vector, in WLANs according to 802.11. This mechanism reduces the probability of collisions. As soon as the RTS/CTS mechanism of a WLAN station is activated, it must transmit the RTS/CTS before the normal data transmission through the frames.
When transmitting data from a WLAN station, it first sends an RTS frame. Both frames, the RTS and the CTS frame, are transmitted at a lower data rate and are therefore received by all stations. The time value of the RTS frame resets the NAV timers of all listening WLAN stations until the transmitted data and the acknowledgement( ACK) have been transmitted. After that, the receiving station transmits Clear to Send (CTS). All stations receiving the CTS frame delay their access by the time requested by the CTS frame.
In addition to the RTS/CTS mechanism, CTS-to-Self is a protection mechanism for mixed operating environments with devices supporting different 802.11 standards. The advantage of CTS-to-Self over RTS/CTS is that the data throughput is higher because fewer frames are sent.