Multiple access with collision avoidance
Multiple access with collision avoidance (MACA) is a slotted media access control protocol used in wireless LAN data transmission to avoid collisions caused by the hidden station problem and to simplify exposed station problem. The basic idea of MACA is a wireless network node makes an announcement before it sends the data frame to inform other nodes to keep silent.
Source: Wikipedia — Multiple access with collision avoidance (CC BY-SA 4.0)