DFS

DFS is short for Dynamic Frequency Selection. It plays a role in 5GHz frequencies that are shared with weather radar.

It is related to 802.11h. DFS support can play a role when using ACS/“survey” in hostapd to find and select free WLAN channels.

Many countries regulate operation on some parts of the 5GHz spectrum - see List_of_WLAN_channels.

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

:!: OpenWrt uses Open Source drivers which might be abandoned by manufactorer or no longer support some 5GHz operation due to regulatory changes.

:!: Original factory drivers can offer DFS when OpenWrt does not.

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

:!: Try to use the non DFS channels if you have old hardware/clients.

  • ath9k: DFS-ETSI, DFS-FCC (source: linux-wireless), probably DFS-JP (git commits)
  • ath10k: DFS-FCC (source: linux-wireless), probably DFS-ETSI
  • mt76: DFS-ETSI, DFS-FCC, DFS-JP. As of 2021-02-22, DFS is unsupported on the 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
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  • Last modified: 2021/02/22 15:02
  • by borromini