Dynamic Frequency Selection (DFS) is a technique used in IEEE 802.11 wireless networks or WiFi that permits devices to dynamically switch the operating frequency of transmission in order to avoid interference with other devices.
DFS is a legal mandate for all IEEE 802.11 devices which share 5 GHz radio spectrum with radar.
DFS was adopted in IEEE 802.11h standard for wireless transmissions. It came up in 2003, when the wireless network started using 5 GHz band that is primarily used by radar systems.
The objective of DFS is to prevent co-channel interference of signals between the primary user, i.e. radar systems, and the secondary users, i.e. the WiFi or WLAN.
DFS allows a router or access point (AP) of a wireless network to detect radar signals in the same frequency spectrum, and change their operating frequency.
The switching of frequency prevents interference between the signals, and assures that the radar systems are able to transmit accurate signals.