The Medium Access Control (MAC) layer is a sub-layer of the Datalink layer that is responsible for managing medium sharing.
Medium access techniques in this section can be characterized as
Random Access technique
no priority, no scheduling, no rules and every node compete to win transmission chance.
Controlled Access techniques
There is a cluster head who arrange transmission schedule or transmission chance is shared fairly among all nodes.
Channelization
The available bandwidth is shared on time, frequency or coding