Two questions from a WiFi newbe

[ar15]

Hi,

I've understood that within the US, channels 1,6 and 11 are preferred to be used in order to avoid interference, In Europe (were I live) we have channels 1 through 13 available. Instead of using only 1, 6 and 11, would it be an alternative for us over here to use channels 1, 5, 9 and 13 instead?

I have attached an inSSIDer snapshot that I made. Some SSIDs, like the Sitecom92EEE4 seem to use channels 11, and every now and then also channel 7 (see the pdf). From what have read on SNB, I conclude that the network switches between 20MHz bandwidth and 40MHz bandwidth. The latter, to my opinion should be avoided in order to avoid interference with my network (I use channel 6). Is my conclusion correct?

 

[sfx2000]

Hi,

I've understood that within the US, channels 1,6 and 11 are preferred to be used in order to avoid interference, In Europe (were I live) we have channels 1 through 13 available. Instead of using only 1, 6 and 11, would it be an alternative for us over here to use channels 1, 5, 9 and 13 instead?

I have attached an inSSIDer snapshot that I made. Some SSIDs, like the Sitecom92EEE4 seem to use channels 11, and every now and then also channel 7 (see the pdf). From what have read on SNB, I conclude that the network switches between 20MHz bandwidth and 40MHz bandwidth. The latter, to my opinion should be avoided in order to avoid interference with my network (I use channel 6). Is my conclusion correct?

This is a decent example of why wide channels are a bad idea in the 2.4GHz band - the sitecom site is causing interference with the neighbors in channel 6, and the Giebels AP in channel 1 is strong enough that if you retune to channel one, you will see degradation there as well unless you can find about 20 dB difference between your AP and the AP in that space...

Depending on the neighboring AP's, what you suggest could work, the 1, 5, 9, 13 (I've seen 1, 4, 8, 11 on some enterprise networks here in the US), but it does take some planning and coordination....

 

[stevech]

remember too, that it's not the number of SSIDs you detect - it's how much air time they use and when. Also called channel utilization

 

[ar15]

Thanks for your replies.

What do you mean by utilization? The networks are on air 24/7.
Futhermore: When are other networks (same channel or different) harmless? When they are >20dB lower than mine? Or....?

 

[stevech]

I should have said "utilization factor" or percentage or busyness.
Like a party line telephone, you don't want neighbors on the same channel (line) that talk (transmit) a lot. You're sharing the air time with others, and due to the overlapping channels in 802.11, the utilization factor (0 to 100%) is the sum of your chosen channel and the two or three adjacent channel numbers.

Ideally, everyone uses only channel 1, 6 and 11 in 2.4GHz. But if you are on channel 3, your receiver sees airtime use from 1,2,3,4,5,6 and maybe 7 too.

So again, it's not the number of SSIDs you see, it the channel utilization factor (busyness). If you had a party-line telephone with neighbors that made very few calls, you'd be happy.

Ordinary WiFi use with a web browser has low utilization, say, 10% or less. Video streaming via WiFi is the culprit in this. Interference to and from neighbors is why one should stream video only on a wired connection - cat5 cable or HomePlug or MoCA.