Point Coordination Function

Point Coordinated Function is a Media Access Control (MAC) technique use in wireless networks which relies on a central node, often an Access Point, to communicate with a node listening, to see if the airwaves are free (ie, all other nodes are not communicating).

Since most Access Points have logical bus topologies, (they are shared circuits) then only one message can be processed at one time (it is a contention based system), and thus a media access control technique is required.

The problem with wireless is that there is a hidden node problem, where some regular nodes (which communcate only with the AP) cannot see other nodes on the extreme edge of the geographical radius of the network (because the wireless signal attenuates before it can reach that far). Thus having an AP in the middle allows the distance to be halved, allowing all nodes to see the AP and consequentially, halving the maxiumum distance between two nodes on the extreme edges of a circle-star topology. (in a circled-star physical topology).

PCF simply uses the AP as a control system in wireless MAC.

Compare with Distributed Coordination Function