RTS/CTS (Request to Send / Clear to Send) is the optional mechanism used by the 802.11 (Standard WiFi) wireless networking protocol to reduce frame collisions introduced by the problem known as hidden node problem. Under this mechanism, specific RTS, CTS and ACK (Acknowledgement) frames are exchanged between the AP and SM to schedule transmission of packets over the wireless link. The ability to use this mechanism is available when Access Point Mode is configured as Standard WiFi (In TDD mode of operation, by design, the hidden node problem does not exist).
Clear to Send mechanism for downlink transmission:
When Enabled the Access Point sends a CTS frame to itself notifying other radios (typically its clients) that it has scheduled transmission of packets on the downlink over the wireless link.
Uplink RTS / CTS
Request To Send / Clear To Send mechanism for uplink transmission:
When Enabled the SM/Client must send an RTS frame and, only upon receiving a CTS frame from the AP can it transmit uplink data over the wireless link. This allows the Access Point to schedule uplink transmission for each client helping avoid packet collisions.
Configure the RTS packet size threshold on the AP for downlink transmission and on the SM for uplink transmission. Typically, sending RTS/CTS frames does not occur unless the packet size exceeds this threshold. If the packet size that the radio wants to transmit is larger than the threshold, the RTS/CTS handshake gets triggered. Otherwise, the data frame gets sent immediately. Default and maximum packet size is 2346 octets.