Carrier Sense Multiple Access With Collision Avoidance And Pilots (CSMA/CAP)

The traditional collision avoidance handshake consists of a request-to-send (RTS), clear-to-send (CTS), a data packet, and an acknowledgment (ACK). However, this system can result in multiple access interference on variable-length data packets and acknowledgements. This can even occur in multi-hop wireless networks when hidden terminals, exposed transmitters, or exposed receivers are present. 

This is augmented with the use of pilot messages. A pilot message is sent by a receiver after it sends a CTS, and a pilot is sent by a sender after its data packet, such that multiple access interference is avoided on data packets or ACKs. The system does not require full-duplex transceivers and can operate using less expensive half-duplex transceivers. There is no need for complex physical-layer techniques. Finally, variable-length data packets can be transmitted without multiple access interference (MAI). ACKs are sent without MAI.