In this lesson,
we're going to explore wireless frequencies.
Now, when I refer to wireless frequencies,
I'm referring to the different frequency bands
that we use to transmit and receive the radio waves
that are being used by our wireless networks to send data.
Each radio signal that's going to be transmitted
or received must be sent or received
at a specific frequency.
Each frequency band has different characteristics
that offer either more speed, more coverage,
or more of both, depending on your needs.
Each different frequency band is also regulated
by governmental agencies to prevent interference
between various communication services.
So it's an important concept for you to understand.
So in this lesson, let's take a look at the 2.4-gigahertz,
5-gigahertz and 6-gigahertz frequency bands
that are used with Wi-Fi networks, including a discussion
about relevant government regulations,
channel sizes, channel widths, and channel overlaps.
Now, the first frequency band that we need
to talk about is the 2.4-gigahertz frequency band.
The 2.4-gigahertz band is one
of the most widely used frequencies for wireless networking
and has been in use since around 1997.
The 2.4-gigahertz band is also known for its long range
and better penetration through solid objects like drywall,
studs, and other types of obstructions.
Now, the 2.4-gigahertz frequency band
actually contains frequencies
from around 2.400 gigahertz,
all the way up to 2.495 gigahertz.
But most people will simply refer to this range
as the 2.4-gigahertz frequency band.
This frequency band is then divided up
into channels using a given channel width,
and these channels will also overlap
with each other, which does cause some interference,
so you need to be aware of that.
Now, when I use the term channel,
what I'm really talking about is a physical medium
through which our wireless networks can
send or receive data.
Now this works much like a physical cable
that we use in our wired networks,
but instead of a physical copper
or fiber cable, we're actually using a virtual cable
that's just using a portion of the wireless frequencies
that exists to create these virtual channels
and send our data through the airwaves using a
specific frequency.
For example, channel one is going to be centered at
2.412 gigahertz.
But since the 2.4-gigahertz band
uses a 22 megahertz channel width,
channel one actually begins around 2.401 gigahertz
and ends around 2.423 gigahertz.
Channel two is centered on 2.417 gigahertz
and begins at 2.406 gigahertz and ends at 2.428 gigahertz.
This continues all the way through
all the channels in the 2.4-gigahertz band.
Now for the exam, you do not need
to memorize the different frequencies associated
with the different channels.
Just be aware that the 2.4-gigahertz band does have a
certain number of channels that you can use,
and in our case, that's either going to be 11, 13
or 14 depending on where you live in the world.
Now, another thing you're going to have to notice
when you look at these channels,
is they actually overlap each other pretty significantly.
Now, within each frequency band,
there are specific frequencies and channels
that we're going to use to avoid overlapping
with other wireless signals in the same area.
Now, the reason for this overlap is
that the government only gave us 72 megahertz worth
of bandwidth for us to use inside
of that 2.4-gigahertz network.
So when we split this up into 11 channels or more,
there's bound to be some overlap
because each channel is going to cover 22 megahertz
out of the 72 megahertz
that the government regulators gave us for our use.
In fact, there are only really three channels
that don't overlap inside the 2.4-gigahertz band,
and these are channel one, channel six, and channel 11.
This is something you definitely want to memorize
for the exam.
If you're using a frequency band
inside the 2.4-gigahertz band,
you should always choose channels one, six
and 11 to avoid any kind of interference
because these do not overlap,
where all the other channels inside will overlap
to some degree.
Now, which channels you can utilize inside
of your 802.11 network is also going to be determined
by your local government's regulations.
Here in the United States, we only have channels one
through 11 for our use.
The same holds true in Canada
and other places in North America.
But if you live in Japan, you actually have channels one
through 14 for your use.
If you live anywhere else in the world,
you can pretty much use channels one through 13,
but again, check your local government regulations first.
Now, because of all the overlapping
and interference that was being caused
by this smaller channel size,
where we have these 22 megahertz channels
all competing for usage,
the newer standards inside the 802.11 wireless system began
to operate inside of a new frequency band,
known as the 5-gigahertz band.
Now, the 5-gigahertz frequency band contains frequencies
from around 5.725 gigahertz, up to 5.875 gigahertz,
and we simply refer to this as the 5-gigahertz band.
Now, due to the larger frequency band allocated
by the government within this 5-gigahertz spectrum
for our wireless networks, we can actually use up
to 24 nonoverlapping channels of 20 megahertz per channel,
when we're working in a 5-gigahertz-based,
802.11 wireless network.
The use of these nonoverlapping channels allows
for less interference and higher levels of performance.
The 5-gigahertz band is preferred for applications
that require higher data throughput,
such as video streaming and gaming.
But it does have a shorter range than
our 2.4-gigahertz band networks do,
and it doesn't penetrate solid objects as well
as the 2.4-gigahertz frequencies do, either.
In addition to using the default channel width
of 20 megahertz within the 5-gigahertz band,
we can also use something known as channel bonding
to create wider channels by merging two
or more of these neighboring channels
into a single wider channel for our data use.
For example, instead of simply using one
of our 20-megahertz channels to transmit our data,
we can instead perform channel bonding
across two channels to provide us with double the bandwidth
because now we have 40 megahertz to work with
instead of 20 megahertz.
In fact, we actually can bond up to eight channels together
inside the 5-gigahertz spectrum to create a
virtual channel that is 160 megahertz in width.
Now, channel bonding is great for increasing the speed
of your wireless network, but you have to be aware
that it does have a potential downside,
because when you use channel bonding,
this can lead to increased channel widths,
like we just said,
and these increased channel widths are more susceptible
to interference because you're reducing the number
of nonoverlapping channels down from 24 to 12,
and then down to six, and then down to three,
and so on depending on how many channels
you decide to bond together.
Now, the newest frequency band
that's used in wireless networking is
actually the 6-gigahertz band.
The 6-gigahertz frequency band is a
relatively new spectrum that was opened up
for Wi-Fi use that offers us even more channels
and bandwidth that allows us to have faster connections
and less congestion.
This 6-gigahertz band is ideal for high density areas
and applications that demand higher speed,
wireless communications.
This 6-gigahertz frequency band contains frequencies
starting at around 5.925 gigahertz,
and goes all the way up to 7.125 gigahertz.
But we still refer to this simply as the 6-gigahertz band.
Now, you may notice that the 6-gigahertz band has the
larger amount of spectrum assigned to it by the government
because we now have 1200 megahertz allocated
to the 6-gigahertz frequency band for use with Wi-Fi
and wireless networking.
Each channel inside this range can either be 20, 40, 80,
or 160 megahertz in size, allowing for as many
as 59 channels when using the 20 megahertz channel width,
and as few as seven channels
when using the 160 megahertz channel width.
Now, the final thing I want to mention is the impacts
of government regulation on our use of wireless frequencies
inside of our networks.
We already discussed how the government allocates portions
of the wireless spectrum for our use inside
of our wireless networks, including small portions
of the 2.4-gigahertz, 5-gigahertz,
and 6-gigahertz frequency bands.
When 802.11a was first introduced
for wireless networking,
it actually used the 5-gigahertz frequency band,
but this was actually causing some issues
with other devices that were already using frequencies close
to that band, like military radar systems
and some types of medical devices.
So in response to this, the 802.11h standard was developed,
and this was done to comply with European regulations
for wireless networking initially,
but its principles have now been widely adopted
in various regions around the globe
because they were very effective
in managing interference and optimizing the
overall use of the 5-gigahertz frequency band.
This 802.11h standard includes some key features,
like dynamic frequency selection and transmit power control.
Dynamic frequency selection, or DFS,
is a feature that requires devices
to actively monitor the environment for radar signals.
If such signals are being detected,
the devices will then switch to another channel
to avoid interfering with those radar systems.
Now, transmit power control, or TPC,
allows your devices to adjust their transmitting power
to the minimum required for maintaining a
good quality connection.
This helps to reduce interference with other devices
and services and also minimizes power consumption,
which can be particularly beneficial
if you're using a battery operated network device.
The last thing we need to cover in this lesson is
something known as band steering.
Now, band steering is a technology
that's used in wireless networking
that optimizes the distribution of your client devices
across different frequency bands.
Typically, this is going to be across the 2.4-gigahertz
and 5-gigahertz bands.
The band steering feature is particularly relevant
for environments where two or more
frequency bands are being utilized
by your equipment and your clients.
Band steering works by detecting your client devices
that are capable of operating on the less congested
and faster bands, like the 5-gigahertz or 6-gigahertz bands,
and then steering them over to that,
leaving the more-crowded 2.4-gigahertz bands
for client devices that only support that frequency.
This can result in a more efficient use
of the available spectral bandwidth,
which reduces interference and improves
your overall network performance,
especially in scenarios where a large number
of devices are going to be present on that network.
This is an intelligent management tool
that helps to enhance our Wi-Fi user experience
by automatically allocating bandwidth resources
in a dual-band wireless environment
to the clients that need it most.
So remember, there are three different frequency bands
that are used for wireless networks, 2.4-gigahertz,
5-gigahertz, and 6-gigahertz.
Each of these has their own characteristics in terms
of data transfer speeds, and the distance
that they can provide coverage for.
When you're dealing with the older 2.4-gigahertz band,
you're going to have the slowest data transfer speeds,
due to having smaller channel widths
and fewer nonoverlapping channels,
which can lead to interference and retransmissions
of your data.
On the other hand, the 2.4-gigahertz band
does provide the greatest distance
in terms of your wireless coverage.
So there is a trade-off here of speed versus distance.
Now, the five-gigahertz band has faster data transfer speeds
than the 2.4-gigahertz band
because it uses a higher frequency
and can support wider channels through channel bonding
by using either 20, 40, 80, or 160 megahertz
in width channels.
This does increase the data transfer speeds,
but unfortunately, it does come at a cost
because 5-gigahertz band frequencies
do provide shorter distances than
their 2.4-gigahertz band equivalents.
Now, the 6-gigahertz band is actually the fastest
of all three frequency bands that we've discussed,
but this is because it uses a higher frequency
and supports channel widths of 20, 40, 80
and 160 megahertz in width.
Of the three frequencies that we've discussed
in this lesson though,
the 6-gigahertz band does provide the shortest distances
for its coverage, and it does offer the
least amount of solid object penetration for our use cases.