CCNA Wireless 640-722 Official Cert Guide

Accessing the Wireless Medium

Once a wireless device has data to send, it must access the network medium and try to send it. Remember that a wireless channel is a shared medium and that every device trying to use it must share the airtime and contend for its use. There is no centralized function that coordinates the use of a wireless channel. Instead, this effort is distributed to each device that uses a channel. This is known as a distributed coordination function (DCF).

With a shared medium, such as wired Ethernet or wireless, two or more stations transmitting at the same time can cause collisions. A collision ruins the transmitted data, wastes time on the medium, and causes the data to be retransmitted—wasting even more time. When full-duplex ...