PHY-Level Collision Avoidance

PHY-Level Collision Avoidance (PLCA) is a component of the Ethernet reconciliation sublayer (between the PHY and the MAC) defined within IEEE 802.3 clause 148. The purpose of PLCA is to avoid the shared medium collisions and associated retransmission overhead.

Source: Wikipedia — PHY-Level Collision Avoidance (CC BY-SA 4.0)