Trying to understand channels and 20/40/80 channel width setting

[telUK]

Hi

I'm trying to figure out what best channel and width to use on my AC86u.

I was using lower channels such as 36,40,44,48 but every so often all be it rare my wifi will drop, might not be linked in any way, so Im trying different channels just to see.

If I select any of the low channels, It seems to select 80mhz .(I use the 20/40/80 auto setting)

If I select channel 136, it selects 40mhz.

Can anyone tell me why this is and if there is any negative effect of using 136 and 40mhz channel width?

Just to add, using a wifi analyser, I see a few networks on channel 36 and 44 in my area, and no one is on the higher channels.

Im in the UK.

Thanks

 

[degrub]

Entire textbooks have been written about why wireless has these issues.

Generally, not having competition from other radios across the entire width of the band used is a good thing. Wider bands, assuming the receiver is capable, also increase the chance of interference from other radios operating on nearby or same bands. Same for physical obstacles that can either reduce the signal strength or reflect the signal causing interference. Sometimes, reducing transmit power can help if reflections are controlling the result.

Radio communication depends on the strength of the signal received at the AP and at the location of the mobile client, not the strength of the transmission point. The weaker of the two receptions will determine the result. So if the AP transmit is strong, but the client transmit is weaker, the client will determine the outcome. If there is local interference, physical or radio signal, near either, then the weaker reception will determine the result.

The two radios are trying to find the channel width for a specific band that provides the highest potential throughput for a given client location. At the lower band channel, a wider band results in more throughput in this case, even with nearby APs operating on the same channels. When higher band channel is selected, the two radios are not able to achieve more throughput with the larger channel width. Whether that higher potential throughput represents a practical improvement is determind by additional factors. In genereal, it should.

 

[telUK]

Entire textbooks have been written about why wireless has these issues.

Generally, not having competition from other radios across the entire width of the band used is a good thing. Wider bands, assuming the receiver is capable, also increase the chance of interference from other radios operating on nearby or same bands. Same for physical obstacles that can either reduce the signal strength or reflect the signal causing interference. Sometimes, reducing transmit power can help if reflections are controlling the result.

Radio communication depends on the strength of the signal received at the AP and at the location of the mobile client, not the strength of the transmission point. The weaker of the two receptions will determine the result. So if the AP transmit is strong, but the client transmit is weaker, the client will determine the outcome. If there is local interference, physical or radio signal, near either, then the weaker reception will determine the result.

The two radios are trying to find the channel width for a specific band that provides the highest potential throughput for a given client location. At the lower band channel, a wider band results in more throughput in this case, even with nearby APs operating on the same channels. When higher band channel is selected, the two radios are not able to achieve more throughput with the larger channel width. Whether that higher potential throughput represents a practical improvement is determind by additional factors. In genereal, it should.

Thanks, I think I will try channel 40 which gives me 80mhz.

I was looking again at my wifi analyser and there is about 4 networks on channel 36, 2 on channel 44 and 1 on 48.

No-one is on channel 40 yet, I will see how that goes, some of my devices seem to prefer the lower channels as well.

 

[gwopman]

My router defaults to 20/40/80 but i limit it to 40 for two reasons: 1) fairly small apartment (>700 sq feet) & 2) heavy wi-fi pollution (city)
I have used 40 for years no problem but 80 seems like it will just cause problems with the amount of competing wifi traffic here.

 

[degrub]

https://www.snbforums.com/threads/channel-width-question.49110/unread

 

[Gar]

https://www.snbforums.com/threads/channel-width-question.49110/unread

The chart is especially helpful in understanding it all, at least for me.