What is going on with channel selection?

[ptselios]

As I try to make my transition from one AP to another, I stuck on a strange finding.

This is what the "Channel Analysis" shows for my AP 1:

As you can see, the selected channel is 48. However, the Local Interface starts at 36!
36 is also the channel of the primary router and this causes issues with "roaming" between the AP.

The /etc/config/wireless has the following entries:

config wifi-device 'radio0'
        option type 'mac80211'
        option path 'platform/soc/c000000.wifi'
        option band '5g'
        option htmode 'HE80'
        option channels '36,40,44,48'
        option cell_density '0'
        option channel '48'

Should I add anything in those entries, or delete the option channels '36,40,44,48' so as to force the radio to work from channel 48?

And why radio0 starts from 36 instead of 48?

[grauerfuchs]

Each channel listed is roughly 20MHz in width. You have 'HE80' set as your mode (80MHz wide), so your device is going to use 4x the space as a single "channel". In the case of channel 48, that means you're using channels 36-48 for your 80MHz signal. Please refer to the channel allocations at https://en.wikipedia.org/wiki/List_of_WLAN_channels to see where the separation points are and which channels are and are not going to be overlapping under each mode.

[mk24]

There are only 5 80 MHz blocks in the band. Choosing any channel within a block has exactly the same result on the air-- the signal always spans from the first to last channel defining the standard block, here 36 to 48. In other words you can't move an 80 MHz signal around in smaller steps.

[ptselios]

I thought the selected channel is at the "center" of the bell, but it looks that it's not.

So, now we fall back to other popular topic "why wifi is not starting when I select channel X" which is really really frustrating because all I get from the logs is

Sat Jan 27 09:20:07 2024 daemon.warn hostapd: wlan0: IEEE 802.11 Configured channel (100) or frequency (5500) (secondary_channel=1) not found from the channel list of the current mode (2) IEEE 802.11a
Sat Jan 27 09:20:07 2024 daemon.warn hostapd: wlan0: IEEE 802.11 Hardware does not support configured channel

while iw list clearly states that channel 100 is available even if it's marked with radar detection and the combination I choose is valid:

        valid interface combinations:
                 * #{ managed } <= 1, #{ AP, mesh point } <= 16,
                   total <= 16, #channels <= 1, STA/AP BI must match, radar detect widths: { 20 MHz (no HT), 20 MHz, 40 MHz, 80 MHz, 80+80 MHz, 160 MHz }

Unless I misunderstand something in the valid combination list, my only solution is to play with the country, although I suspect that this is not going to help me if my devices are set in country A and the AP in country B.

[ptselios]

An update on this.
I manually removed the option channel from the wireless configuration, added the country which was missing (probably forgot to add it in Luci) and I added the

option channels '100,104,108,112,116,120,124,128,132,136,140'

However, now I have another issue! My Guest SSID is not coming up and the logs are full of this entry:

daemon.err lua: (...pkg-arm_cortex-a7/gl-sdk4-repeater/usr/sbin/repeater:368) Wait phy ready...

Hardware is the GL-iNet GL-A1800 Flint.

[ptselios]

No idea why, but it's fixed.

Eventually what I did was to delete the /etc/config/wireless and configure it again, manually this time from the CLI.

Doing so, made each SSID configured in the right place and now all 4 of the SSIDs are active.

[mk24]

@ptselios

gl-sdk4-repeater

This looks like code that is in GL firmware, not official OpenWrt.