Answer:
To avoid collision of transmitting frames.
Explanation:
CSMA/CA, carrier sense multiple access is a media access control protocol of wireless networks that allows for exclusive transmission of frames and avoidance of collision in the network. When a frame is not being sent, nodes listening for an idle channel gets their chance. It sends a request to send (RTS) message to the access point. If the request is granted, the access point sends a clear to send (CTS) message to the node, then the node can transmit its frame.
Many nodes on a wireless network are listening to transmit frames, when a frame is transmitting, the node has to wait for the access point to finish transmitting, so it sends a RTS message again to exclusively transmit a second frame.
