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Following this excellent post, doesn't it mean that if all your neighbours are using 5GHz band, your wifi network will face interference just like the case with 2.4GHz?

For 2.4GHz band, 1,6 and 11 are the recommended channels and are safe to use. Isn't this applied to 5GHz also?

According to physics, high frequency waves overlap each other lesser than low frequency and therefore produce less noise. But waves with similar frequency produce interference independent of their magnitude. It means that even 5GHz band will suffer just like 2.4GHz does.

Another noticeable thing is, in networking we use band and not a particular frequency but even in the case of band your waves is going to be collapsed with your neighbour.

Today, people use dual band wifi routers so in this case overlapping will be much higher than individual bands. Do channels 1, 6 and 11 work in this case?

  • Pretty much none of the statements you make in your question are true. – hobbs Nov 14 '16 at 6:02
  • @hobbs ok then suggest me edit for what is false? – defalt Nov 14 '16 at 6:07
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For 2.5GHz band, 1,6 and 11 are the recommended channels and are safe to use. Isn't this applied to 5GHz also?

No. In the 2.5 GHz band, the channel spacing is 5 MHz. That's why you can only use 1,6, and 11.

In the 5 GHz band, the channels are spaced farther apart - 20MHz, so you can use adjacent channels.

Note that under new FCC rules (in the U.S., of course), some channels are designated for wider bandwidth, to accommodate 802.11n and 802.11ac. In that case, there are fewer channels available.

Today, people use dual band wifi routers so in this case overlapping will be much higher than individual bands. Do 1,6&11 channels work even for this case?

A dual band router just means it has radios that operate in both the 2.5 GHz and 5 GHz band, Some can do either/or, while others can use both radios at the same time (meaning it can have clients on either band). This doesn't affect the channel spacing requirements.

  • So channels are 20MHz apart in 5GHz band, don't 5GHz channels overlap each other at all? – defalt Nov 14 '16 at 4:07
  • @user334283 One other factor is that there are many more channels in the 5GHz band. – Michael Hampton Nov 14 '16 at 5:01
  • I think you are confused about the meaning of channels. The frequency spectrum is divided up onto channels. They are 5 MHz wide in the 2.4GHz band and 20 MHz in he 5 GHz band. They don't overlap. – Ron Trunk Nov 14 '16 at 13:05
  • @RonTrunk In your question you mentioned that channel 6 overlaps with 2 channels up and 2 channels down so I thought that might be a case with 5GHz spectrum too. – defalt Nov 14 '16 at 14:21
  • @user334283 Perhaps I wasn't clear. Channel 6 is only 5 MHz wide (as are all the others). So there's no overlap. But your Wifi signal is 22 MHz wide. So when you transmit on channel 6, your signal covers the adjacent channels. You signal overlaps multiple channels, the channels don't overlap. – Ron Trunk Nov 14 '16 at 14:25
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As Ron already noted, the channel spacing is wider, and furthermore, there are many more 5-GHz band channels available in most countries (particularly for a DFS certified device.) Look here and scroll down far enough to find the 5 GHz channel chart...

https://en.wikipedia.org/wiki/List_of_WLAN_channels

Additionally, a distinct benefit (yes, it's a benefit) of the 5 GHz band is that it penetrates building materials poorly compared to 2.4 GHz. This greatly reduces interference from neighbors, or from your own company's multiple access points. It does make quality installations have more access points (since the end-user device should have a clear line of sight to the AP for best performance), but they interfere less with each other than APs on the 2.4 band.

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