Carrier Sense Multiple Access with Collision Avoidance.
CSMA/CA is a protocol in which a carrier sensing scheme is used. A data station that intends to transmit a frame firstly sends a jam signal. After waiting a sufficient time for all stations to receive that jam signal, the data station then transmits its frame. While transmitting, if the data station detects a jam signal from another station, it stops transmitting for a random time and tries again.
CSMA/CA can use the RTS-CTS exchange as its carrier sensing scheme.