The invention is directed to the optimization of an access to a medium in wireless networks which can be accessed by a plurality of nodes, each node of the plurality of nodes using a medium access mechanism of the Carrier Sense Multiple Access with Collision Avoidance type based on a computation of a backoff value. A specific value is associated with each node of a set of nodes of the plurality of nodes, the specific value of a node being known by the other nodes of the set of nodes. According to the invention, a backoff value is determined for each node of the set of nodes, in each node of the set of nodes, the backoff value associated with a node being determined as a function of the specific value associated with that node.