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- On the 5 GHz spectrum (UNII-2, UNII-2 Extended) most of the channels are used by Wireless systems such as Weather Radar, Military, Airport, harbor, and Satellite communications systems, and the same spectrum is also shared by 802.11 Wireless Networks as well, and this can cause interference to both the systems.
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DFS (Dynamic Frequency Selection) allows FortiAP units to utilize all DFS channels on the 5 GHz spectrum (UNII-2, UNII-2 Extended), and also the FortiAP should comply with permitted transmit power on that channel in that regulatory domain. If a radar event is detected, the FortiAP will automatically change the operating channel on the 5 GHz radio to overcome interference.
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When a radar event is detected on the DFS channels (Channel 52 to 144), the FortiAP would put the detected channel(s) into NOL (Non-Occupancy List), and the FortiAP maintains a list of channels where the radar has been detected. Thereafter, the FortiAP avoids using these channels (NOL) for at least 30 minutes after detecting radar on the channels.
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Radar events can be viewed on the FortiGate WiFi Event logs and also on the FortiAP as shown below:
FortiGate:
date=2024-11-29 time=13:02:32 id=744268591027XXX itime="2024-11-29 13:02:31" euid=3 epid=104 dsteuid=3 dstepid=3 logver=702071577 logid=0104043XXX type="event" subtype="wireless" level="notice" bandwidth="20MHz" action="radar-detected" msg="Demo-AP radio 2 found radar pulse, change channel 104 ==> 104." logdesc="Physical AP radio radar detected" sn="FP431GTY23XXXXX" ip=172.16.X.X ssid="N/A" ap="Demo-AP" channel=104 radioid=2 radioband="802.11ax-5G" configcountry="GB " opercountry="GB " cfgtxpower=1 opertxpower=7 eventtime=1732885351815975289 tz="+0000" slctdrmamode="ap" operdrmamode="ap" devid="FG200FT923XXXXX" vd="root" dtime="2024-11-29 13:02:32" itime_t=1732885351 devname="FG200F"
Related article:
Technical Tip: How to collect logs and config to assist TAC in debugging issues on FortiAP WiFi
FortiAP:
klog | grep Radar
[174785.270285] wlan: [0:D:dfs] WLAN_DEBUG_DFS_ALWAYS : dfs_process_radar_ind_on_home_chan: Radar found on channel=120, freq=5600 MHz. Primary beaconning chan:120, freq=5600 MHz.
rcfg | grep nol
nol list : 60, 64, 124, 128,
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Verify whether there is any External Radar system (Airport/Weather/Harbour/Military) set up near the site. If yes, to minimize radar detections, it is possible to incorporate the following changes:
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Ensure FortiGate is on the newer v7.4.x and above versions because it has new features or enhancement - Wi-Fi 5G Hz UNII-3 channels (149, 153, 157, 161, and 165) are allowed in European countries and region code E countries starting FortiAP v7.4 and FortiGate v7.4 and higher versions and this step will provide more channels for the FortiAP units to operate on the 5 GHz spectrum: New features or enhancements. FortiAP bug id 876673: Wi-Fi UNII-3 channels allowed in certain European countries. FortiGate bug id 852998: Wi-Fi UNII-3 channels should be allowed in certain European countries.
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Deselect all DFS channels from the FortiAP profile on the 5 GHz radio (this step can be suitable for low-density FortiAP deployment).
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Deselect only the frequently detected radar, i.e., no channels from the FortiAP profile from the 5 GHz radio (this step can be suitable for both low and high-density FortiAP deployments).
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Use a 20 MHz channel width on the FortiAP 5 GHz radio.
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Ensure the Distributed Automatic Radio Resource Provisioning (DARRP) feature is enabled on all the radios in the FortiAP profile: Understanding Distributed Radio Resource Provisioning
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Ensure the FortiAP unit is operating on the latest 7.4.x or 7.6.x firmware version
- Avoid using fixed DFS channels because, in a radar event, customers would be without service for at least 30 minutes.
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Useful commands on the FortiAP:
cfg
radartool
radartool -i wifi1 bangradar
klog | grep Radar
iwconfig
date
fap-tech
FortiAP G-series supports UNII-4 channels; this should help include additional channels to the 5 GHz band. Refer to: Configuring UNII-4 5GHz radio bands
Fixes for the known DFS/Radar-related issues are now available on the latest FortiAP v7.4.6 build 0771 GA and v7.6.2 build 0972 GA and higher versions; therefore, for any existing Radar issues, further debugging can be performed after upgrading FortiAP to v7.4.6 or v7.6.2 GA firmware and higher versions:
- 0939375: FortiP-431G/433G moved DFS channels to the NOL list after the radio state changed.
- 1140990: DARRP was skipping available DFS channels that initially detected radar signals, but then later became clear.
See the Resolved Issues section in the FortiAP 7.6.2 release notes or the Resolved Issues section in the FortiAP 7.4.6 release notes.
- Starting FortiOS v7.6.0 and FortiAP v7.6.3 GA and above versions, enable the 'Zero-Wait DFS' feature to minimize DFS Radar event downtime on the 5 GHz radio:
Configuring Zero-Wait DFS
New features or enhancements
Add profile support for Zero-Wait DFS on select FortiAP models
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