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IEEE 802.11 RTS/CTS (request to send/clear to send) is the optional mechanism used by the 802.11 wireless networking protocol to reduce frame collisions introduced by the hidden node problem. Originally the protocol fixed the exposed node problem as well, but later RTS/CTS does not, but includes ACKs.
RTS/CTS (request to send/ clear to send) may refer to: Request to send and clear to send, flow control signals RS-232 RTS/CTS, today's [as of?] ...
Apple's LocalTalk implemented CSMA/CA on an electrical bus using a three-byte jamming signal. 802.11 RTS/CTS implements virtual carrier sensing using short request to send and clear to send messages for WLANs (802.11 mainly relies on physical carrier sensing though). IEEE 802.15.4 (Wireless PAN) uses CSMA/CA
Source: [1] Node D is unaware of the ongoing data transfer between node A and node B. Node D has data to send to node C, which is in the transmission range of node B. D initiates the process by sending an RTS frame to node C. Node C has already deferred its transmission until the completion of the current data transfer between node A and node B (to avoid co-channel interference at node B).
Unlike the original use of RTS and CTS with half-duplex modems, these two signals operate independently from one another. This is an example of hardware flow control . However, "hardware flow control" in the description of the options available on an RS-232-equipped device does not always mean RTS/CTS handshaking.
IEEE 802.11 RTS/CTS mechanism helps to solve this problem only if the nodes are synchronized and packet sizes and data rates are the same for both the transmitting nodes. When a node hears an RTS from a neighboring node, but not the corresponding CTS, that node can deduce that it is an exposed node and is permitted to transmit to other ...
RTS/CTS is not a complete solution and may decrease throughput even further, but adaptive acknowledgements from the base station can help too. The comparison with hidden stations shows that RTS/CTS packages in each traffic class are profitable (even with short audio frames, which cause a high overhead on RTS/CTS frames).
For example, one may imagine a computer sending data to a slow printer. Since the computer is faster at sending data than the printer can print it, the printer falls behind and approaches a situation where it would be overwhelmed by the data. The printer reacts to this situation by sending XOFF to the computer, which temporarily stops sending data.