WEBVTT

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 Hello and welcome to this video called
 planning for RF channel implementation.

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 I've got about five things I'd like to
 cover here and we're going to talk

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 about this concept of non
-overlapping channels.

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 What exactly does that mean?

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 We're going to look at how you design
 for channels in a Wi-Fi layout or

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 topology. We're going to look at 40
 megahertz channels and how does that

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 fit into this idea of non
-overlapping design.

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 I'll talk about the unlicensed National
 Information Infrastructure or

0:00:32.060000 --> 0:00:38.340000
 UNII bands. And we'll see how you can
 utilize the unlicensed National

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 Information Infrastructure bands
 for wider channel bandwidth.

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 Okay, so we know that when you are
 implementing a wireless LAN, which

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 means that you have purchase and access
 point, you place it somewhere

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 on a desk or a wall or a ceiling, you've
 cabled it back into your distribution

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 system, which is your
 wired network.

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 Now it's time to actually
 configure that device.

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 One of the first things you have to decide
 is what channel do I want that

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 device to operate on?

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 And Wi-Fi channels are a different spread
 or a different range of frequencies

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 starting with some lower frequency and
 ending with some higher frequency.

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 And then they modulate the frequencies
 within that range to transmit data.

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 So Wi-Fi channel is technically a range
 of frequencies and the channel

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 number is usually right in the middle
 of that range of frequencies.

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 Now if you see the graphic here below,
 you can see that now this is talking

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 about the 2.4 gigahertz space.

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 And we can see that many of these channels
 have a significant amount of

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 overlap. Why do we
 care about that?

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 What's wrong with having an access
 point in one corner of the building

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 operating on channel one as an example
 and an access point maybe 40 feet

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 away, this operating
 on channel two?

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 They are separate channels, right?


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 Well, in a lot of ways, they're
 not separate channels.

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 Even though they might have different
 numbers, channel one and channel

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 two, we can see here very clearly the
 channel one, the only part of channel

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 one that does not infringe on channel
 two is this little slice right here.

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 So that the frequencies used in channel
 one, those particular frequencies

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 are outside the range
 of channel two.

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 Channel two, the only frequencies he has
 that's outside the range of channel

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 one is this little slice
 of the pie right here.

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 Those frequencies are
 outside channel one.

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 So for example, if I was a client like
 a laptop or a PC or a tablet and

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 I was turned currently tuned in to
 channel number one, I should not be

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 able to hear what this
 stuff in red is.

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 If any of those frequencies are going
 on around me, those are outside

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 of my scope of channel one that I shouldn't
 be paying attention to that.

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 But we can see here that for both channel
 one and channel two, this large

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 section right here is shared
 by both of them.

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 So both channel one and channel two,
 the majority of their frequencies

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 actually overlap, which means that
 accident, we'll just say this right

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 here, let's just say that this
 represents AP number one.

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 Let's say that AP number one right
 now is modulating frequencies that

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 are right about here.

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 That's what he's modulating.

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 And let's say that we have another
 axis point, AP number two, and he's

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 modulating these frequencies
 on channel two.

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 And my client, my laptop, my tablet
 or whatever, is able to hear all of

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 this. So he's right here.

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 Well, now we could have some problems
 because number one, we know that

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 within a range, within a channel, only
 one person's supposed to talk at

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 a time. Well, we could have some problems
 here if axis point one and axis

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 point two start talking.

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 Technically, they're going to be talking
 at the same time because they're

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 using frequency that's
 so close together.

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 They're going to say,
 oh, wait a second.

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 I just heard somebody talking
 is who's doing that?

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 Is that somebody in my BSS?

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 And as far as the client's concerned,
 the radio frequencies, he's not

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 going to know, am I, is the stuff I'm
 hearing right now coming from axis

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 point number two or axis
 point number one?

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 I'm currently associated with
 axis point number one.

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 That's whose BSS I'm
 technically in.

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 But I'm hearing other stuff too, and
 I'm not sure where that's coming

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 from. So this could lead to interference
 and all sorts of problems because

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 we have selected a couple of channels
 that are overlapping, that are using

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 a lot of the same frequencies.

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 So in order to solve this, as we're designing
 a Wi-Fi network, or I should

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 say a Wi-Fi topology, that's going
 to need two or more axis points.

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 Now, if those axis points are so far
 apart from each other, that their

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 BSS's don't touch.

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 In other words, if I have an axis point
 in building number one, and I

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 have an axis point in building number
 four, and there's a lot of walls

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 and stuff in between them, I don't have
 to worry about it if they're both

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 using the exact same channel, if they're
 using channel one and channel

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 two. They're so far apart, their radio
 energy is not being heard by each

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 other. Clients associated to axis point
 number one, won't be able to hear

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 anything from axis
 point number two.

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 But what we're talking about here is
 a situation where axis points are

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 close enough together that a client
 could have that situation we just

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 saw, where it could hear
 from both of them.

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 And this is very common in a lot of
 probably most Wi-Fi implementations.

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 If you're looking at your building,
 for example, and you say, well, my

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 overall goal is I want to have
 continuous Wi-Fi coverage.

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 I don't care if someone's sitting at
 their desk or they pick up their

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 laptop and they move to a conference
 room, or heck, I don't even care

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 if they're in the bathroom.

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 I want them to have Wi-Fi connectivity
 no matter where they are.

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 And simply putting one axis point in
 place is not going to have enough

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 range to hit all points
 in my building.

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 So in that situation, you would intentionally
 design your Wi-Fi layout

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 to have multiple axis points
 all over the place.

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 And you'd want their circles of coverage
 to overlap a little bit so that

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 no matter where you are, you're in
 some Wi-Fi circle, what I call the

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 BSS, the basic service set.

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 Now in that situation, we have to make
 sure that whatever those circles

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 are, so for example, if this is one coverage
 area, and then I've got another

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 coverage area and another coverage area,
 now no matter where I am in this

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 range, I'm going to be in
 range of some axis point.

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 Now I have to think about channel design,
 because putting channel one

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 here and channel two here, if I have
 somebody right here, that's going

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 to be a problem for them.

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 So now's where we want to think about
 what Wi-Fi channels can I use in

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 a situation like this that don't overlap,
 that their frequencies are completely

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 apart from each other.

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 Now in the world of the 2.4 gigahertz
 space, there's three numbers you

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 need to remember when it comes
 to non-overlapping channels.

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 Channel number one, so that would be
 one BSS, then the next channel you

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 would select that doesn't touch that,
 would be channel number six, and

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 then within that same space, the next
 channel would be channel number

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 11. So in the United States, you'll
 see this pattern over and over and

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 over again where companies will use
 channels one, six, and eleven and

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 strategically place them so they can
 have overlapping Wi-Fi coverage,

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 but that the RF signals don't
 overlap with each other.

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 This is what's called non
-overlapping channels.

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 Now you might be looking at this and
 saying, well wait a second Keith,

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 what about channel 14?

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 That's way off to the right.

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 The frequency used by channel 14, why
 couldn't I have a fourth channel,

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 14, and have even more coverage?

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 Well here's the problem.

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 If you're not in the United States,
 yes, you could do that.

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 But here in the United States, actually
 back in 2005, not exactly sure

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 why, the Federal Communications Commission,
 the FCC, actually determined

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 that it was a felony, it was illegal
 to use channel 14 here in the US.

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 Like I said, you'd have to Google that
 and find out the specific reasons

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 for it, but the short story is you can't
 use channel 14 here in the United

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 States. Now, because it is available
 in other places, theoretically I

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 suppose you could buy an access point
 that was made for Japan, and in

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 Japan channel 14 is allowed, and you
 could use that access point here

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 in the US, and hey, now you got channel
 14 available to you, but there's

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 two problems with that.

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 Number one, just because your access
 point here in the US, you've done

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 some finagling, and you've done some
 sneaky business, and now you got

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 an access point that's advertising on
 channel 14, that doesn't mean your

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 clients have the capability
 of listening on channel 14.

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 If I have a laptop or a tablet that
 was produced specifically to be sold

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 in the United States and has a Wi-Fi
 nitcard in that device that was meant

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 to be operated in the United States,
 that Wi-Fi nitcard probably doesn't

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 even look at channel 14.

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 So you could have access points all
 day saying, hey, here I am, I'm on

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 channel 14, and your clients won't even
 know they exist, because the way

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 Wi-Fi clients work is they're periodically
 scanning all these channels,

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 and they do this multiple
 times per second.

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 When it's not actually busy, when the
 client is not actually transmitting

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 or listening to anything, it'll scan
 across all the channels and say,

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 hey, who's out there?

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 What Wi-Fi access points
 are out there?

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 And in the United States, a Wi-Fi client
 would only scan from channels

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 1 to 13, it really shouldn't
 even listen to channel 14.

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 Second problem is, if you try to do this,
 if you try to advertise on channel

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 14, like I said, that is
 technically a felony.

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 The FCC could come after you, and you
 could be slapped with some serious

0:10:02.240000 --> 0:10:06.180000
 fines. I think I even read you could
 be slapped with some jail time by

0:10:06.180000 --> 0:10:07.580000
 advertising on channel 14.

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 So here in the US, just stick
 with channels 1, 6, and 11.

0:10:13.140000 --> 0:10:17.720000
 So keeping that in mind, I'd like
 to give you a little quiz.

0:10:17.720000 --> 0:10:20.960000
 Let's say that this is your
 Wi-Fi layout right here.

0:10:20.960000 --> 0:10:25.140000
 You've got multiple BSSes, and you've
 already determined the channel numbers

0:10:25.140000 --> 0:10:27.020000
 for the top five.

0:10:27.020000 --> 0:10:33.820000
 What channel numbers should you select
 for BSS A, B, and C, so that you

0:10:33.820000 --> 0:10:56.000000
 will not have to use channels
 1, 6, and 11.

0:10:56.000000 --> 0:11:02.300000
 Well, because we have 1 and 6 right
 here, and 1 and 11 right here, let's

0:11:02.300000 --> 0:11:04.300000
 just go with A first of all.

0:11:04.300000 --> 0:11:07.180000
 So if we have 1 and 11 right here,
 let's just go with A first of all.

0:11:07.180000 --> 0:11:07.400000
 So if we have 1 and 11 right here,
 let's just go with A first of all.

0:11:07.400000 --> 0:11:10.880000
 That means this needs
 to be channel 6.

0:11:10.880000 --> 0:11:15.140000
 So let's just put a
 little 6 right here.

0:11:15.140000 --> 0:11:18.780000
 Let's just make that in black
 so it shows up a bit better.

0:11:18.780000 --> 0:11:22.000000
 So that has to be channel 6.

0:11:22.000000 --> 0:11:26.700000
 Now if we take a look at this circle
 right here, if we have 1 and 6, then

0:11:26.700000 --> 0:11:30.220000
 B needs to be 11.

0:11:30.220000 --> 0:11:35.300000
 And then if we take a look at this circle
 right here, 6 and 11, that means

0:11:35.300000 --> 0:11:38.020000
 C has to be channel 1.

0:11:38.020000 --> 0:11:44.960000
 So that's how you would plan out a
 non-overlapping channel situation.

0:11:44.960000 --> 0:11:53.120000
 Now so far, I've really been focusing
 on 20 megahertz channels.

0:11:53.120000 --> 0:11:58.640000
 And 20 megahertz channels were the size
 of your typical channel for most

0:11:58.640000 --> 0:12:00.960000
 of the life of Wi-Fi.

0:12:00.960000 --> 0:12:04.800000
 But then when Wi-Fi standards like 802
.11n started coming out, and I think

0:12:04.800000 --> 0:12:09.180000
 that came out in 2009, the developers
 of that realized, hey, you know

0:12:09.180000 --> 0:12:14.760000
 what, if we expanded the size of a channel,
 then maybe we could have even

0:12:14.760000 --> 0:12:17.560000
 more data sent within a
 given period of time.

0:12:17.560000 --> 0:12:20.140000
 And that's actually
 what 802.11n does.

0:12:20.140000 --> 0:12:23.780000
 Now all these Wi-Fi standards are
 always backwards compatible.

0:12:23.780000 --> 0:12:28.000000
 So for example, when 802.11n came out
 in 2009, I said, hey, if you want

0:12:28.000000 --> 0:12:32.260000
 to get the maximum data rate out of 802
.11n, you need to use a much wider

0:12:32.260000 --> 0:12:36.920000
 channel. But if you've got some clients
 that can't support that or other

0:12:36.920000 --> 0:12:42.100000
 reasons, 802.11n still does support
 the smaller 20 megahertz channels,

0:12:42.100000 --> 0:12:43.580000
 which is what we've
 been dealing with.

0:12:43.580000 --> 0:12:48.180000
 Now we just saw in the previous slide
 that even with a 20 megahertz channel,

0:12:48.180000 --> 0:12:51.940000
 I only had three options if
 I wanted to do non overlap.

0:12:51.940000 --> 0:12:54.360000
 I wanted to do one, six, or 11.

0:12:54.360000 --> 0:13:00.380000
 That was it. So how would I incorporate
 a much twice the width of 40 megahertz

0:13:00.380000 --> 0:13:02.840000
 channel in that same space?

0:13:02.840000 --> 0:13:07.060000
 Well, you can do it, but now instead
 of having three overlapping channels,

0:13:07.060000 --> 0:13:09.060000
 you're down to just two.

0:13:09.060000 --> 0:13:15.840000
 So with 802.11n and AC and AD and AX
 and everything else that comes out

0:13:15.840000 --> 0:13:20.520000
 in the future that's capable of a 40
 megahertz channel, if you're going

0:13:20.520000 --> 0:13:26.800000
 to operate that in the five, I'm sorry,
 in the 2.4 gigahertz space, then

0:13:26.800000 --> 0:13:29.780000
 you've only got two choices.

0:13:29.780000 --> 0:13:33.860000
 Channel three and channel 11.

0:13:33.860000 --> 0:13:37.180000
 Those are the only ways here
 in the United States anyway.

0:13:37.180000 --> 0:13:40.840000
 Actually, even if you, anywhere, if
 you look at this from the beginning

0:13:40.840000 --> 0:13:45.540000
 to the end of the 2.4 gigahertz space,
 there's only, if we sort of move

0:13:45.540000 --> 0:13:49.380000
 these half circles around, there's
 only two places they could ever fit

0:13:49.380000 --> 0:13:51.760000
 where they wouldn't overlap
 with each other.

0:13:51.760000 --> 0:13:55.680000
 So this could cause some problems.


0:13:55.680000 --> 0:14:00.000000
 And remember, and here's the
 other problem with this.

0:14:00.000000 --> 0:14:06.460000
 Remember, here in the US, you're not
 allowed to advertise in that red

0:14:06.460000 --> 0:14:15.700000
 box there. Channel 14 is off limits,
 which means that in the green box

0:14:15.700000 --> 0:14:20.520000
 right here, this portion
 is not allowed.

0:14:20.520000 --> 0:14:25.140000
 You're not allowed to go there.

0:14:25.140000 --> 0:14:28.980000
 So technically, you can't even
 get two 40 megahertz channels.

0:14:28.980000 --> 0:14:31.020000
 You've got one whole one here.

0:14:31.020000 --> 0:14:34.760000
 And this one, you've almost got 40 megahertz
 except this last little slice

0:14:34.760000 --> 0:14:37.400000
 here, you're not allowed to use.

0:14:37.400000 --> 0:14:41.040000
 So if you're going to operate in the
 2.4 gigahertz space, guess what?

0:14:41.040000 --> 0:14:42.960000
 You really only got one option.

0:14:42.960000 --> 0:14:46.860000
 You could move it around, but you've only
 got one BSS you could use because

0:14:46.860000 --> 0:14:50.560000
 there's only one slice of 40 megahertz
 that works that has no overlap

0:14:50.560000 --> 0:14:52.020000
 with anything else.

0:14:52.020000 --> 0:14:53.640000
 So what are you supposed to do?

0:14:53.640000 --> 0:14:57.680000
 Because after all, we want these faster
 speeds that are afforded to us

0:14:57.680000 --> 0:15:03.940000
 with 40 megahertz channels, unfortunately
 for us, the 2.4 gigahertz space

0:15:03.940000 --> 0:15:08.180000
 is not the only industrial and
 scientific medical band.

0:15:08.180000 --> 0:15:11.140000
 There's always the
 5 gigahertz space.

0:15:11.140000 --> 0:15:15.940000
 So this goes into what's called the unlicensed
 national information infrastructure

0:15:15.940000 --> 0:15:24.260000
 bands and divides the 5 gigahertz spectrum
 into four different ranges.

0:15:24.260000 --> 0:15:28.960000
 So each range contains several
 20 megahertz wide channels.

0:15:28.960000 --> 0:15:32.840000
 And notice, they're not
 overlapping at all.

0:15:32.840000 --> 0:15:45.120000
 So for example, here in the low
 range, we've got channel 36.

0:15:45.120000 --> 0:15:47.020000
 So that's 20 megahertz wide.

0:15:47.020000 --> 0:15:51.440000
 If we were actually able to see what
 the actual specific frequencies are,

0:15:51.440000 --> 0:15:54.820000
 we would see from the low to the highest
 20 megahertz, each one of these

0:15:54.820000 --> 0:15:57.120000
 is 20 megahertz wide.

0:15:57.120000 --> 0:16:01.620000
 40, 44, 48, 52, and even these ones
 that are right next to each other,

0:16:01.620000 --> 0:16:03.480000
 they don't overlap.

0:16:03.480000 --> 0:16:09.500000
 The high frequency of one is just below
 the low frequency of the other.

0:16:09.500000 --> 0:16:12.600000
 It's not like the 2.4 gigahertz where
 we had a lot of overlap between

0:16:12.600000 --> 0:16:16.400000
 channels. Now some other things, you
 might be wondering, well, Keith,

0:16:16.400000 --> 0:16:21.380000
 is there any special significance
 between these gaps right here?

0:16:21.380000 --> 0:16:28.360000
 Yes. Here in the United States, these
 gaps represent frequency bands or

0:16:28.360000 --> 0:16:31.200000
 frequency spaces that were
 not allowed to use.

0:16:31.200000 --> 0:16:34.740000
 Once again, the FCC has said, hey, you
 can't transmit on these frequencies

0:16:34.740000 --> 0:16:37.540000
 right here. Don't know why.

0:16:37.540000 --> 0:16:39.660000
 Honestly, it probably doesn't
 really matter why.

0:16:39.660000 --> 0:16:41.620000
 You're not going to be able
 to argue with them anyway.

0:16:41.620000 --> 0:16:46.180000
 But these are areas where there's
 no channels allowed.

0:16:46.180000 --> 0:16:48.720000
 Secondly, the other thing I want to
 point out here is notice how this

0:16:48.720000 --> 0:16:52.820000
 whole thing is divided into
 four different groups.

0:16:52.820000 --> 0:16:57.000000
 And you might think, oh, well, this
 is awesome because with this, I've

0:16:57.000000 --> 0:16:59.160000
 got so many channels
 available to me.

0:16:59.160000 --> 0:17:01.500000
 I can have access points
 all over the place.

0:17:01.500000 --> 0:17:06.740000
 Well, and also when it comes to 40
 megahertz, this is great, right?

0:17:06.740000 --> 0:17:10.880000
 I can have, I can bond these two
 together to get 40 megahertz.

0:17:10.880000 --> 0:17:13.080000
 I could bond these two together
 and these two together.

0:17:13.080000 --> 0:17:18.340000
 I got a lot of choices where I could
 have BSSs that are 40 megahertz wide.

0:17:18.340000 --> 0:17:19.920000
 Well, yes, you can.

0:17:19.920000 --> 0:17:22.280000
 But here's the downside to this.

0:17:22.280000 --> 0:17:28.300000
 Each one of these uni-i bands, the
 low, the mid, the worldwide and the

0:17:28.300000 --> 0:17:31.780000
 upper, have certain restrictions
 that go with them.

0:17:31.780000 --> 0:17:35.900000
 Restrictions concerning things like
 what's the maximum amount of power

0:17:35.900000 --> 0:17:39.300000
 that an access point can
 advertise in that band.

0:17:39.300000 --> 0:17:43.220000
 So an access point that's operating in
 the low band has certain restrictions

0:17:43.220000 --> 0:17:46.680000
 on how much power can use as different
 than something in the worldwide

0:17:46.680000 --> 0:17:48.160000
 or the upper band.

0:17:48.160000 --> 0:17:52.660000
 Also, it has restrictions on what
 type of antennas you can use.

0:17:52.660000 --> 0:17:55.660000
 In the world of Wi-Fi, there's lots
 of different antenna types you can

0:17:55.660000 --> 0:18:00.000000
 select from. There's what's called an
 omnidirectional antenna that radiates

0:18:00.000000 --> 0:18:04.320000
 sort of evenly all the
 way around the antenna.

0:18:04.320000 --> 0:18:06.880000
 And then we can go to the opposite end
 of the spectrum, which is a very

0:18:06.880000 --> 0:18:11.360000
 unidirectional antenna that focuses
 its RF beam in a very specific way

0:18:11.360000 --> 0:18:13.980000
 in a very specific direction.

0:18:13.980000 --> 0:18:18.260000
 Well, in these uni-i bands here, there's
 certain restrictions about what

0:18:18.260000 --> 0:18:21.980000
 kinds of antennas you can use within
 the band and what kinds of antennas

0:18:21.980000 --> 0:18:31.280000
 you can't use. But probably the single
 biggest problem is, and I don't

0:18:31.280000 --> 0:18:34.200000
 know if this is something that's just
 in the United States or not, but

0:18:34.200000 --> 0:18:39.160000
 definitely in the United States, the
 uni-i band is an i-i two band.

0:18:39.160000 --> 0:18:48.420000
 So that would be the worldwide and the
 mid have something called DFS that

0:18:48.420000 --> 0:18:50.080000
 you have to be concerned about.

0:18:50.080000 --> 0:18:52.300000
 What does that stand for?

0:18:52.300000 --> 0:18:55.980000
 DFS stands for dynamic
 frequency selection.

0:18:55.980000 --> 0:19:03.200000
 What's that? Well, as it so happens,
 Wi-Fi is not the only thing that

0:19:03.200000 --> 0:19:05.340000
 operates in the uni-i two bands.

0:19:05.340000 --> 0:19:12.240000
 There are several radars that operate
 in that weather radar, maybe police

0:19:12.240000 --> 0:19:18.520000
 and helicopter radar, but sometimes radar
 stations use the same frequency

0:19:18.520000 --> 0:19:25.960000
 ranges that you find in the uni-i
 two A and the uni-i two C bands.

0:19:25.960000 --> 0:19:32.060000
 And what the FCC has said, they have
 said in this band, radar is much

0:19:32.060000 --> 0:19:34.320000
 more important than Wi-Fi.

0:19:34.320000 --> 0:19:39.620000
 As a matter of fact, it is so important
 that if an access point is currently

0:19:39.620000 --> 0:19:45.340000
 using a channel in those uni-i two
 bands, if that access point detects

0:19:45.340000 --> 0:19:50.960000
 a radar signature using the same frequency,
 that access point should basically

0:19:50.960000 --> 0:19:55.060000
 throw away all of its clients, basically
 say, sorry, clients, I'm gone,

0:19:55.060000 --> 0:19:58.160000
 and it should move over to a
 completely different channel.

0:19:58.160000 --> 0:20:00.820000
 So if you were in the middle of doing
 a stock transaction or something,

0:20:00.820000 --> 0:20:01.680000
 when that happened, guess what?

0:20:01.680000 --> 0:20:04.940000
 You just lost your connectivity
 to your access point.

0:20:04.940000 --> 0:20:07.320000
 That's what dynamic frequency
 selection is all about.

0:20:07.320000 --> 0:20:11.040000
 Dynamic frequency selection says the
 access point is always scanning for

0:20:11.040000 --> 0:20:14.820000
 the presence of radar signatures, radar
 signals, and if it hears a radar

0:20:14.820000 --> 0:20:19.080000
 signal on its same frequency, it has
 to immediately leave that frequency

0:20:19.080000 --> 0:20:23.280000
 and dynamically move
 over to another one.

0:20:23.280000 --> 0:20:27.940000
 So that's why if you take a look at
 how people lay out their channels,

0:20:27.940000 --> 0:20:34.700000
 a lot of times you'll see that people will
 intentionally avoid these channels

0:20:34.700000 --> 0:20:39.640000
 right here. They won't use any of the
 channels in this space because they

0:20:39.640000 --> 0:20:43.720000
 don't want to run the risk of dynamic
 frequency selection being invoked

0:20:43.720000 --> 0:20:47.260000
 and having their customers unhappy because
 they just got knocked off their

0:20:47.260000 --> 0:20:50.340000
 access point and now they have to reassociate
 on a completely different

0:20:50.340000 --> 0:20:53.100000
 channel. And here's the problem.

0:20:53.100000 --> 0:20:56.840000
 If you're the network administrator
 designed this network, do you know

0:20:56.840000 --> 0:20:59.060000
 if there's a radar nearby you?

0:20:59.060000 --> 0:21:01.300000
 If there is, do you know
 what channel it's on?

0:21:01.300000 --> 0:21:04.480000
 There's probably ways to find that out,
 but who would normally think of

0:21:04.480000 --> 0:21:11.280000
 that? So most people in the 5 GHz range
 use the channels in the UNII3

0:21:11.280000 --> 0:21:14.760000
 and the UNII1 band.

0:21:14.760000 --> 0:21:18.500000
 Now you might see stuff in
 the two bands, that's okay.

0:21:18.500000 --> 0:21:28.360000
 It's just you're running a risk
 if you operate in that space.

0:21:28.360000 --> 0:21:33.680000
 So like I mentioned, since 802.11N Wi
-Fi has supported channels that are

0:21:33.680000 --> 0:21:36.740000
 40 MHz and wider.

0:21:36.740000 --> 0:21:42.780000
 802.11AC technically operates
 up to 160 MHz wide channels.

0:21:42.780000 --> 0:21:45.980000
 Well, how would you
 accomplish this?

0:21:45.980000 --> 0:21:49.060000
 So as far as a 40 MHz channel, you
 could do something like that.

0:21:49.060000 --> 0:21:52.380000
 You could say, all right, well I'm
 going to bond 52 and 56 together.

0:21:52.380000 --> 0:21:56.320000
 That'll give me 40 MHz
 wide or 60 and 64.

0:21:56.320000 --> 0:21:58.840000
 So you can see you can
 bond several together.

0:21:58.840000 --> 0:22:02.520000
 If I wanted to do an 80 MHz channel,
 get even faster bandwidth that's

0:22:02.520000 --> 0:22:07.880000
 afforded by 802.11AC, I could bond
 four of those channels together.

0:22:07.880000 --> 0:22:10.880000
 That'll give me 80 MHz.

0:22:10.880000 --> 0:22:14.420000
 One last thing I want to mention is
 you can even bond channels, see how

0:22:14.420000 --> 0:22:18.240000
 in the bottom in the UNII1, the low
 range, you might think, well wait

0:22:18.240000 --> 0:22:20.000000
 a second. What about
 those channels?

0:22:20.000000 --> 0:22:22.760000
 I mean, there's space in between
 there I'm not supposed to use.

0:22:22.760000 --> 0:22:24.060000
 That's all right.

0:22:24.060000 --> 0:22:28.540000
 You could actually bond all four of those
 together into a single BSS that's

0:22:28.540000 --> 0:22:31.000000
 operating at 80 MHz per second.

0:22:31.000000 --> 0:22:37.560000
 All that means is that when that access point
 is oscillating between frequencies,

0:22:37.560000 --> 0:22:41.360000
 it can use the frequencies
 on channel 36.

0:22:41.360000 --> 0:22:46.120000
 It can switch over the frequencies on
 channel 40, channel 44 and channel

0:22:46.120000 --> 0:22:50.580000
 48. It just means that that access point
 is not allowed to use the frequencies

0:22:50.580000 --> 0:22:52.140000
 here in the white space.

0:22:52.140000 --> 0:22:53.640000
 It can't use those.

0:22:53.640000 --> 0:22:58.340000
 But it can still operate, it can still
 advertise a single BSS that's using

0:22:58.340000 --> 0:23:00.800000
 the frequencies across all four of
 these channels, even though they're

0:23:00.800000 --> 0:23:04.700000
 not physically touching
 each other.

0:23:04.700000 --> 0:23:12.220000
 That's why the 5 GHz space is very,
 very popular because when designing

0:23:12.220000 --> 0:23:17.260000
 Wi-Fi LANs, we want to have the largest
 or the biggest width in our channel

0:23:17.260000 --> 0:23:21.440000
 as possible. Remember, the wider channel
 is, the more data we can shove

0:23:21.440000 --> 0:23:24.100000
 down that pipe, the faster
 speeds we can get.

0:23:24.100000 --> 0:23:30.660000
 In the 2.4 GHz space, there's not a lot
 of channels that have non-overlap.

0:23:30.660000 --> 0:23:33.000000
 Most of them overlap a lot.

0:23:33.000000 --> 0:23:36.960000
 As far as a 40 MHz channel,
 there's only one option.

0:23:36.960000 --> 0:23:40.080000
 As far as an 80 MHz channel,
 forget about it.

0:23:40.080000 --> 0:23:43.680000
 You can't do 80 MHz or
 160 MHz in the 2.4.

0:23:43.680000 --> 0:23:47.840000
 You've got to go into
 the 5 GHz range.

0:23:47.840000 --> 0:23:53.080000
 And so that concludes this video on
 Wi-Fi channels and non-overlapping

0:23:53.080000 --> 0:23:57.040000
 channels. And I hope you found
 this video to be helpful.

0:23:57.040000 --> 0:23:57.700000
 Thank you for watching.