DFS

Dynamic Frequency Selection plays a role in 5GHz frequencies that are shared with Terminal Doppler Weather Radar (TDWR). It is related to 802.11h.

DFS support is used during ACS/“survey” in hostapd to find and select free WLAN channels.

Many countries regulate operation of the 5GHz spectrum - see List_of_WLAN_channels & DFS/TPC channel information.

Due to fast development, changing hardware, regulatory changes and compliance issues there can be interoperability issues.

OpenWrt uses open source drivers with varying quality and upstream support. Sometimes they may be abandoned by the manufacturer, or no longer support some 5GHz operation due to regulatory changes.

OEM proprietary drivers can sometimes offer DFS channel where OpenWrt opensource drivers cannot.

There are different DFS schemes: DFS-FCC (USA), DFS-ETSI (Europe), DFS-JP (Japan).

Try to use the non DFS channels if you have older wifi hardware/wifi clients.

In addition: See also FAQ - What does DFS mean? & Wireless FAQ section for more information.

• ath9k: DFS-ETSI, DFS-FCC (source: linux-wireless), probably DFS-JP (git commits)
• ath10k: DFS-FCC (source: linux-wireless), probably DFS-ETSI
• ath11k: DFS-FCC (source: linux-wireless), probably DFS-ETSI
• mt76: DFS-ETSI, DFS-FCC, DFS-JP. As of 2021-02-22, DFS is unsupported on MT7613 radio however, despite the hardware supporting it.
• mwlwifi (source:linux-wireless), but support is problematic on some hardware and won't be fixed (GitHub issue #75)
• mwifiex (source: git log: “DFS support in AP mode”,kernel.org)

• ath9k_htc
• wlcore, wl18xx (allow using dfs channels,add radar_debug_mode debugfs file for DFS testing)
• brcmfmac
• brcmsmac
• b43

• mwl8k