Zero-wait DFS

Dynamic Frequency Selection (DFS) is a mandate for radio systems operating in the 5 GHz band to identify and avoid interference with Radar systems. IEEE 802.11h is the standard that covers the usage of DFS channels. To make use of DFS channels, wireless access points need to be certified to ensure that WiFi services on AP do follow the rule, e.g., stop immediately when a Radar signal is detected.

Since only a few business or enterprise APs are certified to use DFS channels, DFS channels are generally not so crowded in comparing with non-DFS channels. Network providers like to use DFS channels because of less interference. However, for the area with occasional Radar signals, service providers tend to avoid DFS channels.

According to the 802.11h standard, an AP must immediately switch channels if a radar signal is detected on its current DFS channel. Since moving to a new DFS channel requires the AP to remain silent for one minute to ensure radar absence, APs generally switch to non-DFS channels to avoid service interruptions for wireless clients, ensuring compliance with standards.

Instead of falling back to the non-DFS channel, Zero-wait DFS provides seamless change of channels. That is, stations do not lose their connectivity when an AP moves to another DFS channel. With the dedicated scanning radio, EnGenius ECW220S/230S APs can always guarantee the one-minute clearance of the target DFS channel hence hop to that channel without any waiting.

When an AP changes its channel, Channel Switch Announcement (CSA), as defined by IEEE 802.11h, is adopted to announce that AP is switching to a new channel before it begins transmitting on that channel. This allows the clients, who support CSA, to transition to the new channel with minimal downtime.

Go to Configure > Access Point > Radio to enable the Zero-Wait DFS feature.