Hello everyone and welcome to a wireless section in your Encore course. Now Raymond is taking you
through networking with various wired solutions. We are now going to begin talking about a wireless
portion. Now this is recorded only. Hopefully you guys have taken the time to view this obviously.
But the reason we are doing this as an addendum is because there's so much here in wireless that
it would be tough to cover in a live course and tough to cover well. Wireless is something I've
taught several times in my career obviously but it's something that is a very tough technology
to get right. It's its own CCIE discipline. It is very difficult from a perspective of
understanding how the signal flows through the medium of air. So what we're going to do is we're
going to focus, hyper focus on the certifications and what's required to actually pass the exam.
Now if you want to dive into the wireless technology and I like it, it's one of my favorite
things, you should. But right now what we're going to do is we're going to dive into just what you
need to know for the certification. I'm going to show you different websites and things like that
to dive into but let's go ahead and go into our first lesson. Our first lesson is all about layer
one wireless. Now I do need to give you some background information here when we're going
through wireless and how it works. So some of this stuff will not be exam relevant but you need to be
able to understand it for the exam. So let's jump into what wireless is. First off, wireless is
is a signal. That's all it is. We have signals that go along copper lines but now we have signals that
go in the air. We are pushing this out into everything around you. Wireless signals are
flying around from everything like audio. Someone just speaking. Looks like I forgot to press the
button. So let's go back to this. Let me press the button and hopefully it'll let me draw. Yes, okay.
So audio is the first. The voice right now, what you're hearing is a signal, believe it or not, is a
wireless transmission. We're doing wireless communication right now. The sound, it carries
a signal to your eardrums and that vibration is then
is then understood by your brain and then your brain turns it into a meaning, right? This is not
all that different from the wireless we receive here, this spectrum. Now this is from, we'll talk
a little bit about this, but this is from 2.4 to 6 gigahertz. Now 6 gigahertz is a new range but
that's kind of where we are right now with wireless. We have these bands that are specific
for wireless communication and the reasoning for that is why don't we use all of this? Why
aren't we using in the terahertz or the petahertz or the exahertz? Why aren't we going way up the
scale, right? That means that's more data we could throw. No, the reason is there are
different things that live in these areas. Here we're talking about light and here's where humans
can see. This is the visible spectrum. We can start seeing those wavelengths. Here we have
microwaves and things like that. That's why a microwave is a huge bit of trouble in your
wireless environments if it's leaking. We've got TV, we've got FM radio, we've got AM radio,
ampular and frequent modulation. We've got another TV band here. Even in this range right here,
we have some emergency communication depending on where you are. So we have lots of these waves and
since we share the same medium, since it's all in the air, you are overlapping with other frequencies
the key is we can't use the same frequency at the same time. Once you start doing that, it creates
interference. So I'd like to show you what this kind of looks like in our frequency bands.
If we're looking at our frequency bands and what different wireless protocols use, 802.11a,
the first kind of real standard we were using, was at 5 gigahertz and then the 802.11b started
using the 2.4 gigahertz and then 802.11g is 2.4. Now a lot of you guys are probably wondering,
what's the difference? Why does it matter if I'm using 5 or 2.4? Well, 2.4 is an actually,
it's a longer wavelength. Remember, this is frequency. When I draw a wavelength, this is
the frequency from here to here, from the top point to the top point. How fast does that happen?
Hertz. It's how many times per second. So this gigahertz, we're talking thousands of times per
second. 5 gigahertz, this little cycle right here, from here to here, will happen twice as fast
as it does in a 2.4 gigahertz. So what we're seeing is we're seeing shorter wavelengths,
more energy going into it. What that means is the distance is shorter
for 5. It's a shorter distance. 2.4 can travel in longer distances.
But here's an interesting thing to remember. If I can travel a shorter distance, but I'm going
twice as fast, the frequency is jumping up and down twice as fast, I can move more data.
Now there's a lot that goes into how much data you can move at any given time,
but that's the general gist of it, right? There's scatter, there's interference,
there's things that come into play on how much data you can actually move. But in general,
if you are close enough for the AP to 2.4 and 5 gigahertz to be effective,
5 gigahertz will transmit more data. And you can kind of see this. If we look at this, 802.11a was
54 megabits per second. When we went to B, look at the drop, 11 megabits per second. But we got
more distance out of that. When we go back to G, we're seeing 2.4 at 54 megabits per second.
They were more efficient, there were algorithms employed, there's different things like that.
Then we got to N. N is when we started saying, oh, we'll use both. We'll use 2.4 and 5. This
is more for backwards compatibility at the time. And then we saw a jump to 450 megabits per second.
Compare that to the other speeds we're seeing, right? That's a huge leap. It's almost tenfold.
Then we start to get into AC. Some of you out there will call it Wi-Fi 5. That's when we really
started using that naming convention. And that was at 5 gigahertz. And look at the speed,
up to 7 gigabits. Now, there's a big asterisk next to all these speeds. We'll talk about it a
little later. But that was a theoretical top of where you could get. Not really what you're seeing
in the real world. But that's what in labs, when there's no interference, when you're standing
right next to the AP, that's the kind of speed you could expect. Now, when we look at AX, this
is called 6. And we'll talk about 6E in a second. I didn't forget. You get 2.4 and 5 for the original
AX or Wi-Fi 6. That had a speed up to 10 gigabits per second in a lab environment again. And then
we introduced 6E. That's a second standard. It's still qualified under the AX. But it was a new
standard that was released by the Wi-Fi group. This allowed us to get to 10 gigabit-ish,
right in there, 9.1 or something like that, gigabits per second. And this, again,
was in the lab environment. But what this represented was a drastic increase in speed
and real world speed at that, not just in the lab. The theoretical top limit was the same.
But as we moved forward with the 6 gigahertz range, we started to see improvements in real
world speed. And that brings us up to the newest, latest, and greatest 802.11 BE. Everybody you know
will call it Wi-Fi 7. Wi-Fi 7 uses all of these. It has radio wave standards. It's got new algorithms.
It's got more antennas supported. All those things do not necessarily translate into everyone's
device because devices need specific antennas that are enabled for the BE or 7 standard.
So just because it says, I believe it's 8x8 or 16x16, antennas does not mean that's supported
and does not mean you get to use all those antennas. I really suggest you dive into a
wireless class here. There's a lot of marketing that takes place that kind of
rolls over into wireless purchases that don't necessarily translate into speeds for your users.
So something to pay attention to. Now, the important part of wireless
is understanding the signal you're receiving. That's really where we need to pay attention
in our wireless environments. Obviously right now even, if you look in the lower right hand
side of your computer, you're probably going to see a signal strength indicator.
What that kind of goes on is this. It's really all about measuring dBms, decibel per milliwatt or
decibel milliwatts. So what this is, is the power you are putting into the signal and projecting it
out. Decibel is a generic way to measure things by strength. I'm not going to dive into it. That's
a deep wireless class. But decibel is just a reference measurement. So if I start somewhere
and I increase the decibels, I am increasing that relative to where I began. So if I have
a measurement on how much power I'm actually putting into the air or the signal, I can then
transfer it into a decibel. So when I say dBm, that's decibel milliwatts, that is the increase
or decrease of power based on my reference point. So decibels to a milliwatt. Please remember that.
And also, please remember that these are usually, almost always, measured in a negative.
Now, why a negative? Well, if you think about it, if it is a reference measurement and I'm
going through the air, I'm going down a cable, I'm doing things. Think of it like friction
here on earth. If I drag a mouse across the table, there's friction and the energy I put in
is kind of drawn down. That scraping across the table creates a little bit of drag, which means
the energy I'm putting in the mouse is not actually everything I'm getting when I move
the mouse. I'm getting only a percentage of what I put in. And that's what we're seeing with dBm,
decibel to milliwatts. I put in 100,000 watts and I throw it out in the air. When somebody is
receiving a signal, they're not receiving 100,000 watts. Because think of it this way,
it goes up the antenna, it goes everywhere. You're only receiving a small fraction of that.
So you're not going to receive the full signal transmission. That's why we measure this in
negatives because you're losing signal. Now, how much you lose is very important to keep track of.
And I'd be remiss if I didn't say this, some vendors drop the negative because it's confusing
to people. They shouldn't, but they do. So there we go. So dBm, decibel to milliwatt,
it's the easiest and most consistent way to use this. Not all people pay attention to it.
You'll see some vendors not use dBm, but for this, for your understanding, dBm is the easiest
way to get there. So strength of the signal. Like we talked about, this gives me an idea.
When we're talking about dBm, we're talking about signal strength.
Now, here's an important thing to understand. If a signal has plus 3 dBm, we are adding signal
strength. So plus, we are going up. And like we just said, negative means the signal strength
is dropping. So if I say, I'm going to put, we got 20 dB going out right now. I'm going to put it to 23.
What have I done to that signal? Well, let's say, and please, we're just using numbers here.
Let's say this is 100 watts of power I'm putting into it. Don't think about this too much. Okay,
that's way too much power. But if I put 100 watts into the air there, if I go to 23,
that's 200 watts, roughly. This is a power of 3. There's an actual equation that you don't
need to memorize. But this is what I would like you to remember. And very important,
if I was going to sit and take some type of exam on this, is I would definitely understand that
plus 3, signal's going up by double the power. Minus 3, I'm dropping power in half.
Very important to realize and understand. Next up is our Received Signal Strength Indicator,
RSSI. It's important to understand here that this is not standardized. There's no Wi-Fi body
or approval or, this is not an open standard published by IANA or any other organization.
It's not an open standard published by IANA or any of the other major internet providers,
even the Wi-Fi Council. But it is a way that a lot of people measure this. Indicators 0 to 60
in some vendors, 0 to 255 by some vendors. And this will determine that little Wi-Fi signal thing
if you're watching this on wireless. This is what a lot of vendors use to determine,
oh, your Wi-Fi signal is low. You only have one bar or six bars or whatever.
This is not a standardized issue. I just want you to be aware that it's there.
So let's dive into signal strength. So we talked about negative 30 dB or 30 dB or how these ratings
are all negative. Let's talk about negative 30, the very top, and we'll jump to the very bottom.
It's important you understand this list, by the way, understand what's ranking here,
and we'll go through it a little bit. But let's start at top and bottom. Negative 30 dBm. I know
what you're saying, negative 30. Goodness gracious, you've lost a lot of power from
that antenna. You're receiving negative 30 from zero. That signal strength has dropped quite a
bit. But remember, let's talk about what we said earlier, where that signal is being pushed out in
every direction, in a direction through a wireless space. So you're pushing this signal through the
air towards a direction, or in some case in an omni-directional, in every direction.
So people will only receive a fraction of the signal you are sending out. Negative 30 dBm is
amazing. That means you are likely sitting next to the AP. You're right next to the AP. This is
basically lab environment type signal strength. You're not going to see this in an office
environment or here or there or anywhere where there's interference. This is the golden standard,
right? Let's talk about the bottom. Negative 90. Now remember, we drop by a power of 2 for
every 3 dBm. And we've dropped 30 dBm. So that's 10 times you're having that signal.
That's incredibly lower. It's a factor of 10 worse than the signal you received at the very best.
This is unusable. Negative 90 means people are not connecting. The data is, you may get a
connection and drop, connection and drop. It is not ideal for any type of data transfer.
Okay, so let's go in the middle. What is good? What are we looking for? Well, VoIP, which is a
very important, very resource-intensive streaming service, right? And then streaming video. Well,
we only need negative 67 for that. Our signal strength, we've lost some signal, but we haven't
lost at all. This is a very good, this is the top of the line. If you're getting negative 67 dBms,
you're doing great. That's like a 4-bar, 5-bar situation whenever your operating system shows.
Now 70 dBm, maybe you're a little farther away from the access point. Maybe you don't have great
signal strength. Maybe there's a lot of interference and a lot of offices near you.
Channels are overlapping for different SSIDs, and it's not a great system.
You can still get on the web and you can still do email. That's usually the case.
And then when we go to negative 80, that's not good at all. People are dropping in and out.
Can't be used for VoIP, definitely. Can't be used for voice. Not good for web traffic. This is just
bad. You don't want to download. You don't want to stream. Nothing even close here.
Notice that from here to here, 67 to 70, what's our dB difference? Well, that's a negative 3,
isn't it? We've dropped 3 more. And negative 3 means the signal is what? Halved. So from here
to here, we've lost half the power of the signal. Okay, we're going to keep revisiting that just so
you get an idea. You start getting that reference in your mind of how it works.
So I mentioned something in the last slide that we need to really talk about. I said
interference. You might have other channels or other things using the same frequency as you.
This brings up a good question. How much is too much interference? Well, honestly,
it depends on your signal and how much background noise, or in this case, noise we have in our
environment. To figure this out is noise floor. That's here. This is the noise floor. And then
you take out the received signal. Now remember, you receive all of the signal.
And you need to take out – sorry, my shoulder's in the way. You need to take out the noise floor
because really, this is only the viable signal you're going to receive. This area in here,
like it says, SNR, the dB. That's what you're really going to see because the signal, the
noise floor is going to cancel out any of the signal you have in the same space.
Think about if I was talking very quietly and we were whispering about something,
and then other people are whispering at the same time. You're not going to hear it. It cancels
each other out. But as I raise my voice over that whispering or that background noise,
you're going to hear me more and more. That's exactly the same as the signal you receive.
And this is why the signal-to-noise ratio is a very important calculation.
So how do we calculate this? Well, we take the signal and subtract the noise.
It's not that difficult. Let's say the signal we receive is negative 65 dB. Let's roll back.
Negative 65 dB. That's where they should be. Negative 65 dB. Oh my gosh, they're on the upper
range of good. Very good here. Ooh, good. Excellent. So we're good, right? Well, no.
We have to subtract out the noise. Well, now the noise is negative 90.
So this is the received signal strength indicator, the RSSI. Remember, non-standardized.
Negative 65. And then we need to subtract out what? The noise floor. So let's do this calculation.
RSSI minus noise. Remember, these are both in decibel milliwatts. So we go negative 65
minus a negative 90. Well, I got two negatives. That gives me a positive. Let's see. That would
be 25. I'm getting a received signal strength of 25. That's what I'm receiving. Let's take a look
at where that falls. If the SNR is in 25, let's look. Voice has a minimum of 25. I can barely
use voice. That's the strength I'm at. Interesting. You see how we've changed where we were?
If we roll back, we were initially... I'm rolling all the way back here. We were initially at the
very high end here. We started at negative 65. Now, I understand we're changing charts,
but it's important to understand the difference between RSI, received signal strength indicator,
versus our initial signal strength. Remember, this is at the top of VOIP. I was at the top of VOIP,
but there's so much noise there that I actually ended up dropping to the very bottom of VOIP,
because when we look at this table for SNR, it says that once I take out my noise floor,
if I'm at 25 received signal strength, that's not a good place for voice. I need to try and
improve that. I'm at the very minimum. It's very important that you know that 25 and 20
are very, very important numbers. One is the voice minimum, 25, and one is the data minimum,
which is 20. In order to remember this, voice alphabetically comes after data. Look at the 25
and 20. 25 comes after 20. That's how I remember it. So, data minimum is 20, voice is 25. Another
way you can remember this is, remember our powers of three? Well, our powers of three said that
every three decibels, I'm doubling the strength of the signal. This is five, so this is almost
four times as powerful, or double and double again, two to the power of two.
So, do I need a higher signal strength for voice? Yes, absolutely. So, that's another way you can
remember it. You start at 20 with data, you need to up the signal strength to get to 25.
Now, how do we take all this into account? What determines my noise? How does that
come into play? Well, it really, really depends on what channels you use. Now, channels are very
important in understanding that your traffic travels in a channel. Now, they say the 2.4 range.
They say 2.4 gigahertz. Everybody's using 2.4 gigahertz. Now, is that strictly true? Absolutely
not. If you take a look at this, you're actually using only a fraction of the channel. If we take
a look at this channel here, we've got 1, 6, 11. These are common channels used in the 2.4 gigahertz
range. And what this shows is we have a 22 megahertz channel width. So, if I take a look at
2.4 to 2.42, it's actually 2.4 to 2, we would see that here to here is a channel. And if I take 22
more, here to here is a channel. And here to here is a channel. Those are non-overlapping channels.
Why? Well, let's take a look. Let me erase this. Let's dive a little deeper into this.
If I have a channel, let's say I'm using channel 3, and I'll highlight this in red,
pink. I'm using channel 3, and let's say a neighbor's using channel 1. Channel 3 is
not a standard channel. I have an overlap here. You see this area here?
This is an overlap in channels. What do I get if I'm using channel 1 and my neighbor is using
channel 3? What I get is interference on anything that is transferred in this frequency range right
here. That frequency range, probably 2.412 to 2.422. Any data that's actually being moved in
that range, the signal loss is going to happen. Remember the RSSI we talked about? The signal
to noise ratio? We've introduced now here in this channel, we just introduced interference
because we're both using overlapping channels. That's why in the United States
and in other places, we use non-overlapping channels. Channel 1, channel 6, and channel 11
for 2.4. Now, other types of devices use other channels, so you've got to be careful on what's
around you. Walkie-talkies, old cordless phones from when I was young use 2.4. There's lots of
things that use radio waves, so you've got to be careful. Here, Japan and other places have
opened up channel 14. In the U.S., this is not viable for the U.S. You cannot use this. The FCC
will get mad, and they'll yell at you. There are emergency communication channels that communicate
over that, and we do not want to create interference over those communication channels,
so they cannot speak. But in other countries, it's okay because they don't use those channels
for emergency communication. Does that mean we're off the hook when we use 5 gigahertz?
Absolutely not. I want you to take a look at the 5 gigahertz range. Here, you can see we do have
channels. It's 0.020 or 20 megahertz is the channel width. You can see that we have multiple channels
here. What you'll notice, though, is we have many, many more channels. So this, in an office environment,
will create much, much less interference because my neighbors could be using 100, and I could be using
140, and they will never, ever interfere with each other. So that's why in office environments in the
modern world, we often see people using the 5 gigahertz standard, and that is a more modern
approach to wireless networking in an enterprise environment, is using the larger gigahertz.
Now, 6 gigahertz does not need to be talked about in this course, but here, we'll talk about the 5
gigahertz range. Now, there's something very interesting that happens from here to here.
So, see 52, 56, 60, 64, 100, 104, 108, all the way to 140. Notice that there's a plus 4 here for every
jump. Just be aware. I mean, that's not exam relevant, but you'll begin to see this more and
more. It's plus 4. Let's take a look at what happens within that range. Remember I said that
not everyone uses, not everyone, not every frequency is dedicated just to wireless?
Well, here is something very important to understand in the 5 gigahertz range.
Weather uses radar. Hospitals have different magnetic resonance machines and different types of
things they radiate out. We got airplane radar. Well, those mostly fall in the Uni2 and Uni2
Extended. If I roll back, Uni2 and Uni2 Extended. I marked those as important. Look at those channel
numbers. Okay. If you are near an airport or a hospital, and I mean really near because 5
gigahertz doesn't travel very far, but even if you're in a hospital, it's important to realize
you may be creating interference. If you're in an airport with wireless,
you may not want to use those channels. You may want to disable DFS, and those DFS rules only
apply to the 5.2 to 5.7 gigahertz range. Just be very cognizant of using the 5 gigahertz range
if you're in those industries. Hospital, weather, Doppler radar, news station,
if you have Doppler radar, if it's on your roof, airplane, definitely pay attention to those.
All right. That was it for that lesson. We will dive into antenna types in our next lesson,
but in our last lesson, we talked about the medium of wireless, using the air to
send out signals. Very important as a basic or basic understanding.
We will dive into how antennas shape that in our next lesson. Thank you. Bye.