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Tiv
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Wi-Fi auto channel select & N-only

Tue Nov 05, 2019 4:54 pm

Hello !

I want to buy a router for home
1) there is free channel auto-detection for 802.11n 2.4 GHz and 5 GHz
if so, according to what algorithm (CCA or another) and with what frequency - once every hour or somehow
2) for 802.11n 2.4 GHz and 5 GHz, is it possible to set "N-only" mode

thank
 
mkx
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Re: Wi-Fi auto channel select & N-only

Tue Nov 05, 2019 10:20 pm

1) there is free channel auto-detection for 802.11n 2.4 GHz and 5 GHz
Default setting is to allow unit automatically choose suitable channel. It is possible to set a channel or list of allowed channels.

if so, according to what algorithm (CCA or another) and with what frequency - once every hour or somehow
No idea about that.

2) for 802.11n 2.4 GHz and 5 GHz, is it possible to set "N-only" mode
There's a setting to do that. I never tried it so I can only guess that it actually works.
BR,
Metod
 
Zacharias
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Re: Wi-Fi auto channel select & N-only

Tue Nov 05, 2019 10:32 pm

I don't think any algorithm is used. Probably the less crowded frequency is used...
Also in case you select channel widths with XX and XXXX extensions automatically scan for a less crowded control channel frequency based on the number of concurrent devices running in every frequency and chooses the “C” - Control channel frequency automatically.
Source : https://wiki.mikrotik.com/wiki/Manual:I ... e/Wireless

N only mode works just fine...
 
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CZFan
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Re: Wi-Fi auto channel select & N-only

Tue Nov 05, 2019 10:53 pm

When wireless interface starts up, it will scan and select channel with the least number of "networks".

If you get a router with a mode button, you can configure a script to disable wireless for couple of seconds and enable again which will cause router to rescan frequencies, else you will have to do this manually by logging into router or restarting router
MTCNA, MTCTCE, MTCRE & MTCINE
 
Zacharias
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Re: Wi-Fi auto channel select & N-only

Tue Nov 05, 2019 11:36 pm

Or you can setup capsman manager and configure reselect interval parameter...
 
Tiv
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Re: Wi-Fi auto channel select & N-only

Wed Nov 06, 2019 3:08 pm

But can you set in capsman manager interval of 15 or 20 minutes of automatic channel selection ?

Can I exclude some channels from auto-selection?
My Wi-Fi adapter does not support all channels in the 5 GHz band, so if auto-selection of an unsupported channel occurs, communication with the router will be lost ...

For 802.11n 2,4 GHz and 5 GHz you can set the channel width to 40 MHz, not dynamic 20/40 MHz ?

Under the channel auto-selection algorithm, I assumed any adequate algorithm (CCA - Clear Channel Assessment) or another.
On some routers, I saw automatic selection algorithms comparing Rx Tx with incomprehensible limits, for example, 10 KB / s or 100 KB / s.
Based on these comparisons, another channel was selected.
It is not clear why the firmware developers chose some incomprehensible limits ...
I think such channel auto-selection algorithms in routers are inadequate.
 
Zacharias
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Re: Wi-Fi auto channel select & N-only

Wed Nov 06, 2019 3:55 pm

Yes you can set an interval of 15 minutes...
Create a channel list and the selection will be according to the list...

No you can not set a width of 40 Mhz only...
 
Tiv
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Re: Wi-Fi auto channel select & N-only

Wed Nov 06, 2019 4:08 pm

(I'm sorry, I don't know much English I use a translator)
But you can’t tell me why it’s impossible to set the channel width to only 40 MHz? At OpenWRT or DD-WRT you can
 
mkx
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Re: Wi-Fi auto channel select & N-only

Wed Nov 06, 2019 4:27 pm

wikipedia has some explanation ... seems like this is done for backward compatibility. It shouldn't really affect performance when N-capable client connects a dual channel-width AP. It might, however, help with interference: if there are non-N APs around, they won't be able to identify 40MHz channel as used and might use sub-channel ... thus increasing interference for the 40MHz "network". Something similar actually happens even with 20/40 setting, but non-N APs will only interfere with "extension" channel ...
BR,
Metod
 
Tiv
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Re: Wi-Fi auto channel select & N-only

Wed Nov 06, 2019 4:41 pm

Thank
I'm not good at networking, trying to understand something.
I saw that in OpenWRT or DD-WRT I can set the channel width to only 40 MHz.
Did I understand correctly that only 20/40 MHz can be set in RouterOS even if all my clients are 802.11n ?
 
Zacharias
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Re: Wi-Fi auto channel select & N-only

Wed Nov 06, 2019 6:34 pm

Did I understand correctly that only 20/40 MHz can be set in RouterOS even if all my clients are 802.11n ?
802.11n does not mean channel width of 40 Mhz only...!
802.11n operates at 20Mhz as well...
 
mkx
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Re: Wi-Fi auto channel select & N-only

Wed Nov 06, 2019 7:34 pm

I saw that in OpenWRT or DD-WRT I can set the channel width to only 40 MHz.

I don't have any experience with xxWRT, but reading OpenWRT wiki, it seems that setting option 'ht_mode' 'HT40' (or some variant of HT40) actually works exactly the same as ROS setting "20/40" ... also in OpenWRT there will be primary/control channel and secondary channel. The setting doesn't require client devices to use 40MHz wide channel at all times.
BR,
Metod
 
Zacharias
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Re: Wi-Fi auto channel select & N-only

Wed Nov 06, 2019 7:55 pm

I do not think that by adjusting the high throughput (HT) rates you can force the use of only 40 Mhz channel width since all rates work on both 20Mhz and 40Mhz as well...
So any rate can give you 20 and 40 Mhz as well...
Also 40Mhz width means 2x20Mhz channels...!
 
Tiv
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Re: Wi-Fi auto channel select & N-only

Wed Nov 06, 2019 10:54 pm

By description, HT40 means in OpenWRT always 20 MHz + 20 MHz, not Dynamic...
https://oldwiki.archive.openwrt.org/doc ... ce_options

In DD-WRT
https://forum.dd-wrt.com/wiki/index.php ... nnel_Width
1) Dynamic (20/40 MHz) [as in the RouterOS]
2) Wide HT40 (40 MHz) [absent in the RouterOS ?] always 20 MHz + 20 MHz
In terms of performance, is 20/40 MHz still worse than 40 MHz (always 20 MHz + 20 MHz) if all clients only 802.11n ?
 
Zacharias
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Re: Wi-Fi auto channel select & N-only

Wed Nov 06, 2019 11:42 pm

You can achieve 40 Mhz channel width with the use of extention channel 20+20Mhz ( channel bonding )...
When channel width is 20/40 (20+20)Mhz then both can be used, when channel width is 40 (20+20)Mhz then only 40 Mhz are used...That is the difference...
There is no 40Mhz channel in real, it is always a result of channel bonding (20+20) !!!
 
Tiv
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Re: Wi-Fi auto channel select & N-only

Thu Nov 07, 2019 12:37 pm

Zacharias, mkx Thanks you

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