RTS/CTS Frames

Request to send (RTS) and clear to send (CTS) frames are used to enhance the virtual carrier sense process. For a client station to participate in a basic service set, it must be able to communicate with the access point. This is straightforward and logical; however, it is possible for the client station to be able to communicate with the access point but not be able to hear or be heard by any of the other client stations. This can be a problem because a station performs collision avoidance by setting its NAV when it hears another station transmitting (virtual carrier sense) and by listening for RF (physical carrier sense). If a station cannot hear the other stations or cannot be heard by the other stations, there is a greater likelihood that a collision can occur.