A method of controlling access of mobile users of a substantially infrastructureless communications network to a shared communication medium, wherein the shared communication medium is partitioned into a plurality of individual communication channels that can be individually exploited for communications between the network users. The method includes determining the existence of at least one main direction of movement of the network users, the main direction of movement being a direction around which directions of movement of a prescribed number of network users are clustered; associating a group of communication channels within the plurality of communication channels to the at least one main direction of movement; and reserving the communication channels of the group to the network users moving substantially in the main direction of movement.