contention window (802.11) (CW)

In the collisionless access methodCSMA/ CA used in WLANs, there are several waiting times before a station can access the transmission medium.

The Interframe Space( IFS) and the techniques derived from it play an essential role in priority control and quality of service in 802.11 radio LANs. In addition, there is the Contention Window(CW), which intervenes when stations have waited for the same interframe space before transmitting and then want to access the radio medium.

For this case the Contention Window defines a random time span as backoff. The CW period is between a minimum and a maximum value and is doubled for each collision that occurs. This procedure is comparable to the Binary Exponential Backoff( BEB) in CSMA/ CD.