5GHz Spectrum

by | Sep 24, 2020 | Blog

5GHz spectrum, the spectrum for the rest of us.

In today’s training video we’re going to talk about the 5GHz spectrum and how it can help you have better Wi-Fi.

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5 gigahertz spectrum, the spectrum for the rest of us

In today's training video we're going to talk about

the 5GHz spectrum and how it can help you have better Wi-Fi

5 gigahertz spectrum, it's a spectrum for the rest of us

We've talked earlier about the 2.4 gig spectrum

and we will be talking about the six gig spectrum that's coming

in some of the countries around the world

But today we're going to talk about 5 gigahertz

and why it can help you have better Wi-Fi

First up, again, we're going to look at the ruler

and compare the size, the physical size

of a 2.4 gig wave to a 5 gig wave to a 6 gig wave

The wave length is the form that you can see on the screen

We're taking the speed of light, dividing it

And coming up with this size, it's tied to frequency

And so as we have as you see in the center here,

there is a difference between 2.4 and 5 gig

5 gig has a lot more frequencies available to us

Well, the frequencies are available

in all of the different radio frequencies

It's just, can we use them in Wi-Fi?

And we have a lot more spectrum in Wi-Fi, so much more

that there's actually a slight difference in the size of the wave,

as we go from the bottom to the top,

So as we change from the low end of 5 gig to the higher end,

the frequency changes a little bit

The wave length will change there as well

At the bottom here, you can see there's also a formula

you can look at if you want to come up with the formula

for what is the channel, you just use the formula and say, well,

we're going to take 5000 plus five times the channel numbers

If I'm Channel 36, you multiply that times five

and you come up with a number

Actually, I never got good at keeping those numbers

and the formulas is in my head

So instead I came up with the chart and the chart

allows us to see all the things that are available to us in 5 gig

We have different countries on the left

So let's get in and see what this chart tells us

and drill down a little bit

Yeah, old man eyes, I got to get the glasses on

So if you look over here under the frequency,

we have the radio bands and they have names

U-NII 1, U-NII 2, U-NII 2A, 2B, 2C

There's a couple of these that we have access to

and a couple that we don't

The U-NII, U stands for

Unlicensed National Information Infrastructure

These were frequencies set aside specifically for data

Which means we're not going to be running into other things

like portable phones or microwave ovens or

other things in this range

But we may run into other data based systems that don't use it,

802.11 they might use their own proprietary function

But these are available, U-NII 1, U-NII 2, U-NII 3

And so that's that's the radio band itself

If we look over here, it says the past proposal

you need to be was a proposal

We were looking to say this would be a great chunk

of spectrum for Wi-Fi

We applied the FCC looked at it and said

there's some incumbents in there

We just can't get those incumbents to move

On the other hand, you need to see was also had incumbents

and they were running a lot of other things in

their harbor radar, aircraft, radar, Doppler radar

Different things that were using these frequencies that would

have made for really good Wi-Fi frequencies

And so we went to the, you know, international body and said.

Can we use these?

And basically, well, the EU kind of led the way and said,

we'd like to use this

How about if we figure out a way that we can use it nicely?

We know we are not the incumbent,

we are not the primary user

But, you know, I live in Utah

We don't have a lot of water

It's a big desert

So when I go down and say, can I use harbor radar frequencies,

there are no harbors here

So no one's using harbor radar frequency

Can I use it?

And the answer, they came back and said, OK,

if we follow the DFS rules, we can use it

Now we can have another video and talk about how

the DFS rules work

But these that have the DFS on them and it's up at the top

DFS channels up there

Mean, you have to follow the DFS rules

if you're going to use them

If you're going to use them, great

Just make sure that they aren't being triggered a lot

So we have the U-NII 2 band here

Sorry, U-NII 1, U-NII 2, U-NII 2C, U-NII 3

And then there's a proposed U-NII 4

this one hasn't finished yet

We still might be able to pull off

And it's the band that right before we move to the 6GHz

there is one channel that's right over here to the right side

that right now doesn't look like we'll be able to get

So we won't have a contiguous chunk

Would have been nice,

but we still have to play nice with all the other neighbors

Now, if you look down here, there's a 20 megahertz channel

and for 20 megahertz channels, obviously not very wide,

only 20 megahertz wide

This 20 megahertz is for OFDM

In the early days of 802.11 primary called the, you know,

classic like classic coconspirators, 802.11 classic,

and then a move to B, G cetera

In the B and the classic, we use 22 megahertz wide channels

for the reasons of the modulation schemes use at the time

As we went to G and went to OFDM,

we dropped them down to 20 megahertz

So we now are looking at 20 megahertz channels

In the US we have 25 of them available

40 megahertz channels twice as wide

But that means a couple of things

One, we can send twice as much information

Just great

As you go to 40 megahertz wide channels,

they're twice as wide

Meaning you are going to send twice as much information

They also are listening to twice as much noise

So the noise floor is twice as wide, which means our SNR drops

by 3 dB as we go wider

But we go wider, we can now go faster, but we now have fewer

We only have 12 of those channels to choose from

So the rule for using channel width is use the

widest channel you can until you can't

How do you know you can't

when you get code channel interference

So I like using wide channels

At my house I use 80 megahertz channels

Nothing wrong with that

As long as there's no neighbors also using the same

80 megahertz wide channel

If you're in a in a school environment, an office environment,

in a hospital environment, you probably don't have enough

free space in the frequencies to use 80 megahertz channels

You're going to have code channel interference

And so I would rather have two separate channels

each 40 wide than one 80 that has

two AP on the same channel

So going narrower is better not because we don't go faster,

but because we have more control

We don't have code channel interference

Code channel interference like the killer of Wi-Fi

two APs on the same channel have the capacity of one

if they see each other

So you don't get extra capacity by adding another one

So pick your channel with appropriate to wherever you are

Now, if we come down, the chart also shows FCC

it has different rules as you go to different countries

ISED in Canada, ACMA in Australia, ETSI in the EU,

I didn't have enough to put all the

different countries or regions in here

One, I didn't know them all

So I did the research on these and add them to the table

But as you can see, there's different transmit powers

Different things work in the U.S.

The yellow colored ones, 120, 124, 128 were for the

Doppler radar and we lost it for a while from the FCC

then they gave it back

So those are there

But in Canada and Australia, you still can't use them

They never gave those back

In the EU you can see you can use them outdoor, but you have

to change your scan time to a longer period

If you're on those three channels

There's also another channel, 149 up here

We have to look at 149

165 is only a 20 megahertz wide channel

there's no forty's around

So if you're doing with the 40 channel everywhere,

just realize whoever hits 165 is going to be there as well

Another thing you look at is a website called

clients.michaelbano.com and you can go look up your

individual clients and see in a table which of these

5GHz your channels, your client support

There is times years ago where you could buy a whole lot of

clients that didn't support individual ones

So Channel 149 is one that some didn't support 144

There was a period of time where clients didn't

And then we went to Acee and it became a new thing

and it got available

So check your client load and make sure they support

the channels and then you use those channels

As far as DFS channels go, use all of them until you can't

How do you know when you can't when you get DFS events

happening regularly

If you get a rare DFS event that there's a channel change that

happens, watch it and then check your logs

And if it's happening a lot, then you can pull that individual channel, every channel, LAN

5 gigahertz, look at all that space

It's kind of sad to realize we lost the U-NII 2B

And as of right now, it does not even on the dock

or anywhere to get it back

But we have U-NII 1, U- NII 2, U-NII 2C, U-NII 3 available

lots and lots of channels to choose from

Use 5 gig, it's the frequency for the rest of us

If you have any more other questions or we want to see more

videos, training videos like this go out to WLANPros.com

We also have podcasts, we have blogs,

we have all the WLPC videos

Be glad to have you be part of the community

Thank you

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