5GHz resets to channel 36 (from configured channel)

Software SW bugs discussion
1

My Omnia is running with latest 3.11.7. But I had this at least with 3.11.6 as well.

My 5GHz WLAN is usually running on channel 64. This works for some time, but then suddenly the interface changes back to channel 36.

# iw dev wlan0 info
Interface wlan0
	ifindex 21
	wdev 0x7
	addr ...
	ssid ....
	type AP
	wiphy 0
	channel 36 (5180 MHz), width: 80 MHz, center1: 5210 MHz

while

config wifi-device 'radio0'
	option type 'mac80211'
	option hwmode '11a'
	option path 'soc/soc:pcie-controller/pci0000:00/0000:00:02.0/0000:02:00.0'
	option country 'AT'
	option htmode 'VHT80'
	option txpower '20'
	option channel '64'

luci displays the difference as well (36 active, 64 configured). Disabling and enabling the interface “fixes” it.

This time it happend while I was streaming a Video. It suddenly stopped and I can’t reconnect for some time (DFS delay?).

There is no output in dmesg or messages from the kernel. Only hostap reauthenticates all devices after some time.

2

This is expected behaviour - channel 64 is DFS and wpad scans every now and then for DFS channel interferences.
It seems channel 64 is used in your area so either choose non-DFS-channel or use trial&error until you find out, which DFS-channel is not used by weather radar in your area.

3

according to information in the web (eg. funkfeuer) there is only one weather radar near LOWW which uses channel 120-128. I see no reason why 64 should not work indoor. And it works for weeks or at least days. Is there a way to see some debugging output which notes the DFS triggered change?

4

Unless otherwise regulated in AT it is governed by https://www.etsi.org/deliver/etsi_en/301800_301899/301893/02.01.01_60/en_301893v020101p.pdf

  • Table 12: Minimum number of burst detections for channels within the 5 600 MHz to 5 650 MHz band
  • DFS applicable frequency range

And it should indeed but

Whilst being the latest release in the 3.x branch the OS and its components are quite outdated and wpad (version) is know as buggy in that. It probably works better with TOS4.x, if not then TOS5.x

5

Channel 64 requires DFS in the EU. Manufacturers that interfere with licensed spectrum users face liabilities and regulatory actions, those that do not might mildly annoy the few of their own customers who actually might notice. IMHO any manufacturer will opt for accepting more false positive Radar detections to avoid false negative Radar-Non detections, I would not be amazed if you just encounter occasional false positives on channel 64… Or maybe even correct detections, some frequencies are also used by military radars and these might be mobile and/or their position and activity periods might not be publically announced.

6

According to
https://www.rtr.at/en/tk/Spektrum5GHz
channels below 100 need no DFS in Austria.


defines the same. But maybe I got something wrong here. I’m not an expert on this topic.

dfs_stats for athk10 states
Radars detected : 3

Maybe something coming from CZ or SK?

Since TOS4 was finally released recently I’ll give it a try in the next days.

7

OpenWrt relies on https://git.kernel.org/pub/scm/linux/kernel/git/sforshee/wireless-regdb.git/tree/db.txt?id=HEAD#n90

country AT: DFS-ETSI
	(2402 - 2482 @ 40), (20)
	(5170 - 5250 @ 80), (20), AUTO-BW, wmmrule=ETSI
	(5250 - 5330 @ 80), (20), DFS, AUTO-BW, wmmrule=ETSI
	(5490 - 5710 @ 160), (27), DFS, wmmrule=ETSI
	# 60 GHz band channels 1-4, ref: Etsi En 302 567
	(57000 - 66000 @ 2160), (40)

country CZ: DFS-ETSI
	(2400 - 2483.5 @ 40), (100 mW)
	(5150 - 5250 @ 80), (200 mW), NO-OUTDOOR, AUTO-BW, wmmrule=ETSI
	(5250 - 5350 @ 80), (100 mW), NO-OUTDOOR, DFS, AUTO-BW, wmmrule=ETSI
	(5470 - 5725 @ 160), (500 mW), DFS, wmmrule=ETSI
	# 60 GHz band channels 1-4, ref: Etsi En 302 567
	(57000 - 66000 @ 2160), (40)

country SK: DFS-ETSI
	(2402 - 2482 @ 40), (20)
	(5170 - 5250 @ 80), (20), AUTO-BW, wmmrule=ETSI
	(5250 - 5330 @ 80), (20), DFS, AUTO-BW, wmmrule=ETSI
	(5490 - 5710 @ 160), (27), DFS, wmmrule=ETSI
	# 60 GHz band channels 1-4, ref: Etsi En 302 567
	(57000 - 66000 @ 2160), (40)

With channel 64 - 5320 MHz DFS would apply for all three countries.