From the course: Wireless Networking Essential Training

5 GHz channels

From the course: Wireless Networking Essential Training

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5 GHz channels

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- In addition to the 2.4 ghz frequency band, another popular band of frequencies that are commonly used in a Wifi networks is the 5 ghz frequency band. And the good news is, the 5 ghz frequency band is not nearly as congested as our 2.4 ghz band. Instead of having only three non overlapping channels, we said we could have channels one, six, and eleven that did not overlap with the 2.4 ghz band. Instead of just having those three non overlapping channels, with the 5 ghz band we have lots of channels. In fact, we have over 29 overlapping channels. In here, I'm running a wifi analyzer on my computer and it's showing the channels that are being used by some access points in my network. Now something that's not obvious, is the way the channels are numbered. Notice down here, it looks like we're jumping from channel 36, directly to channel 40. It looks like we're skipping channels 37, 38, and 39 but, interestingly that's just the way the usable channels are sequentially numbered. We cannot send an access point to operate, for example on channel 37. So even though it looks like we're skipping numbers, these are really consecutive channel numbers. And normally, I'll tell my access point to choose on its own in appropriate channel. So normally I don't have to do anything, it's going to listen to neighboring access points, and it's going to try to avoid overlapping frequencies. And even though I said that we have non overlapping channels here in the 5 ghz band, that's only if we're using 20 Mhz channels widths. Here, if you take a look at one of my access points, I'm using an 80 Mhz channel width. So in this case, I actually am spanning a few different channels. So if you're statically configuring your channels on the 5 ghz band, remember that one channel is not going to bleed into another, like we did with the 2.4 ghz band, but that's only guarantee that if you're using the 20 MHz channel width. If you start using a larger channel widths, like 40 Mhz, 80 Mhz, or even now 160 Mhz, you need to keep that in mind and spread your channels a little further apart to avoid them still bleeding from one into the other.

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