[Solved] How to avoid DFS RADAR frequency with auto channel

Installing and Using OpenWrt
1

Hi there. I live near a air force base, after installing OpenWRT, I have been experiencing disconnections in the 5GHz frequency band every day for the past two days. The log is as follows.

Wed Feb 21 09:49:33 2024 daemon.notice hostapd: phy1-ap0: DFS-RADAR-DETECTED freq=5580 ht_enabled=0 chan_offset=0 chan_width=5 cf1=5570 cf2=0
Wed Feb 21 09:49:33 2024 daemon.notice hostapd: phy1-ap0: AP-DISABLED
Wed Feb 21 09:49:33 2024 daemon.notice hostapd: phy1-ap0: AP-STA-DISCONNECTED ma:ca:dd:re:ss:00
Wed Feb 21 09:49:33 2024 daemon.notice hostapd: nl80211: deinit ifname=phy1-ap0 disabled_11b_rates=0
Wed Feb 21 09:49:33 2024 daemon.notice netifd: Network device 'phy1-ap0' link is down
Wed Feb 21 09:49:33 2024 kern.info kernel: [62705.033256] br-lan: port 7(phy1-ap0) entered disabled state
Wed Feb 21 09:49:34 2024 daemon.notice hostapd: phy1-ap0: interface state ENABLED->DISABLED
Wed Feb 21 09:49:34 2024 kern.info kernel: [62706.326341] br-lan: port 7(phy1-ap0) entered disabled state
Wed Feb 21 09:49:34 2024 kern.info kernel: [62706.333303] device phy1-ap0 left promiscuous mode
Wed Feb 21 09:49:34 2024 kern.info kernel: [62706.338109] br-lan: port 7(phy1-ap0) entered disabled state
Wed Feb 21 09:49:35 2024 kern.info kernel: [62707.174445] br-lan: port 7(phy1-ap0) entered blocking state
Wed Feb 21 09:49:35 2024 kern.info kernel: [62707.180023] br-lan: port 7(phy1-ap0) entered disabled state
Wed Feb 21 09:49:35 2024 daemon.notice hostapd: phy1-ap0: interface state DISABLED->COUNTRY_UPDATE
Wed Feb 21 09:49:35 2024 daemon.notice hostapd: ACS: Automatic channel selection started, this may take a bit
Wed Feb 21 09:49:35 2024 kern.info kernel: [62707.185770] device phy1-ap0 entered promiscuous mode
Wed Feb 21 09:49:35 2024 daemon.notice hostapd: phy1-ap0: interface state COUNTRY_UPDATE->ACS
Wed Feb 21 09:49:35 2024 daemon.notice hostapd: phy1-ap0: ACS-STARTED
Wed Feb 21 09:49:52 2024 daemon.notice hostapd: phy1-ap0: ACS-COMPLETED freq=5620 channel=124
Wed Feb 21 09:49:52 2024 daemon.notice hostapd: phy1-ap0: interface state ACS->HT_SCAN
Wed Feb 21 09:49:52 2024 daemon.notice hostapd: phy1-ap0: interface state HT_SCAN->DFS
Wed Feb 21 09:49:52 2024 daemon.notice hostapd: phy1-ap0: DFS-CAC-START freq=5180 chan=36 sec_chan=1, width=2, seg0=50, seg1=0, cac_time=60s
Wed Feb 21 09:50:57 2024 daemon.notice hostapd: phy1-ap0: DFS-CAC-COMPLETED success=1 freq=5180 ht_enabled=0 chan_offset=0 chan_width=5 cf1=5250 cf2=0
Wed Feb 21 09:50:57 2024 daemon.warn hostapd: Can't set DFS state for freq 5180 MHz
Wed Feb 21 09:50:57 2024 daemon.warn hostapd: Can't set DFS state for freq 5200 MHz
Wed Feb 21 09:50:57 2024 daemon.warn hostapd: Can't set DFS state for freq 5220 MHz
Wed Feb 21 09:50:57 2024 daemon.warn hostapd: Can't set DFS state for freq 5240 MHz
Wed Feb 21 09:50:58 2024 kern.info kernel: [62789.392083] IPv6: ADDRCONF(NETDEV_CHANGE): phy1-ap0: link becomes ready
Wed Feb 21 09:50:58 2024 kern.info kernel: [62789.398814] br-lan: port 7(phy1-ap0) entered blocking state
Wed Feb 21 09:50:58 2024 kern.info kernel: [62789.404384] br-lan: port 7(phy1-ap0) entered forwarding state
Wed Feb 21 09:50:58 2024 daemon.notice netifd: Network device 'phy1-ap0' link is up
Wed Feb 21 09:50:58 2024 daemon.notice hostapd: phy1-ap0: interface state DFS->ENABLED

I have already set the country code to SG

# iw reg get
global
country SG: DFS-FCC
	(2400 - 2483 @ 40), (N/A, 23), (N/A)
	(5150 - 5250 @ 80), (N/A, 23), (N/A), AUTO-BW
	(5250 - 5350 @ 80), (N/A, 20), (0 ms), DFS, AUTO-BW
	(5470 - 5725 @ 160), (N/A, 27), (0 ms), DFS
	(5725 - 5850 @ 80), (N/A, 30), (N/A)
	(57000 - 66000 @ 2160), (N/A, 40), (N/A)

From the above output, I can confirm that DFS frequency is in the range defined. But when the channel is set to auto, the router still cannot avoid the DFS frequency band. What should I do? Thanks in advance.

1 Like
2

Is there a reason you can’t use a manual channel selection?

1 Like
3

Yes. I tried a few channels, for example 149 153 161 and etc,. If I set the fixed channel, 5g wifi some cases shows disabled, and some cases no signal.

Details of the no signal: normally it shows -xx/-92 dBm, if I set manualy it shows /-92 dBm and devices cannot find 5g SSID

One more reason, I was wondering auto channel could help with confilicts with neighbour wifi.

The device is XDR6088 and firmware is 23.05.2 official build

Edit: later I found that 160Mhz only works with channel 36 and 100, this is the reason why 5g wifi no signal after manually setting.

4

I have figured out the reason.

When the 160 MHz channel width is enabled, there are only three continuous blocks of channels that you can actually use - these are channels 36 to 64 and 100 to 128 and 149-177. Please note that 177 are not allowed in most countries.

If you need to use a 160 MHz width, manually set the channel number to 36, as this width implies that the client covers the whole 36-64 channel block. 36 is the ultimate solution for most users.

For me, I need super high speed wireless speed because landlord does not allow me to drill a hole for each room to connect cable.

My solution is using channel 100, and change the SSID same to 2.4G. Thus even DFS radar detected, my ongoing call wont be disturbed. So far this solution works good.

Btw, channel 100 is around 20% faster than channel 36.

5

That is great that you figured it out but you left out important information e.g. you were trying to use 160 width.

As for the US: 36 and 145-161 are the most congested and 165 is legally limited to a 20 width but is still, highly, congested.

The best channel is a clear channel with room for desired width without overlapping the neighbors.

2 Likes
6

With 160 MHz channel you will cause and suffer quite a lot of interference from other APs on overlapping frequencies, so I would always try whether 80MHz channels are not in practice better.
Personally I opted for Cat6 flat cables temporarily 'glued' to the baseboard/skirting, that might not be the most beautiful or elegant solution, but it delivers 1 Gbps rate robustly and reliably...

3 Likes
7

Totally agree with you. I'll try flat cables too... Experimenting with 160MHz bandwidth is quite a hassle.

The experience of stable 1Gbps is much better than unstable >~1Gbps wireless :cold_face:

1 Like
8

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