Let's take a moment to drill deeper into this conversation about high density
designs.
Because a lot of our wireless networks these days have to be designed to
support a lot
of wireless stations.
We think about maybe a high school gymnasium that could support hundreds of
wireless devices
at a time.
Well that's very high density.
And again, back when I was doing wireless surveys, a school gymnasium would get
a single
access point because there was nothing stopping the wireless signal and all we WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
access point because there was nothing stopping the wireless signal and all we
cared about
was coverage.
And so the 10 or 15 wireless devices that showed up could use the Wi-Fi.
But again, now you've got bleachers full of people.
You've got dozens, if not hundreds of people all there.
And they've all got a cell phone that they might try to attach to the Wi-Fi.
Well at that point, we're going to need a little bit of a change in our
philosophy
for how we are going to complete these high density designs.
And again, at this point, we are focused on capacity, not coverage. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And again, at this point, we are focused on capacity, not coverage.
It's very easy to get wrapped up in the coverage conversation and make sure we
have wireless
signal everywhere.
And forget about the fact that capacity is what really determines the success
these days
of a wireless design.
So there's a few things to keep in mind.
First of all, we already mentioned the multi-cell concept where we can have an
overlapping
cell on a single access point or multiple overlapping cells. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So we can deploy lots of these together.
And ideally, we hope that there's a distribution of the wireless stations among
the bands.
Now there is work at being able to direct wireless stations to balance out a
little bit.
For example, I might have a wireless station that tries to associate on one of
the five
gigahertz bands and the AP says, "Hey, you know what?
You should go look at the other five gigahertz band.
Maybe this is channel 48.
And I want you to look at channel 64 because channel 48 has 35 stations on it. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And I want you to look at channel 64 because channel 48 has 35 stations on it.
Channel 64 has 15."
And so these are methods that are being developed even today to try to help to
deal with these
high density types of deployments.
But it does start by having multiple cells overlapping one another.
But then we do need to ask the question about bonded channels.
We covered bonded channels earlier on.
The idea here is that I'm going to take to a J-cent 20 megahertz channels and I WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
The idea here is that I'm going to take to a J-cent 20 megahertz channels and I
'm going
to combine them together into one large 40 megahertz channel.
And then I can do this to combine two separate 40 megahertz channels into an 80
and to 80s
into a 160.
The cool thing about bonded channels is it gives me a whole lot more of that
wireless real
estate, which means I can transmit on more frequencies.
And this in the end, it gives me a whole lot more wireless throughput. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And this in the end, it gives me a whole lot more wireless throughput.
So bonded channels very, very good for throughput.
But again, when we're talking about a high density wireless deployment, we're
not as concerned
about throughput.
So this is another thing that we have to consider.
It's not just capacity versus coverage.
So it's also a conversation about reliability or maybe a robust network versus WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
So it's also a conversation about reliability or maybe a robust network versus
throughput.
Because having higher throughput is great for a single user or maybe we've got
a bunch
of devices that really need high throughput.
But we wouldn't have 35 or 50 of these devices in theory.
At that point, what we care more about is reliability and being able to
maintain a connection.
And so yeah, the bond to channels are great for throughput, but they're not so
good for
reliability. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
reliability.
Meaning that we are going to have reliability.
We're going to have a lot more stations.
Again, crowding the space.
We're going to use up our channels faster because now if I'm having, you know,
I've mentioned
two five gigahertz channels, well, if those are bonded, now I'm going to use
four of those
channels on the same physical space.
So four channels here and four channels here and four channels here.
I start to run out of even five gigahertz channels pretty quickly. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
I start to run out of even five gigahertz channels pretty quickly.
And furthermore, it's a lot harder to transmit on a 40 gigahertz channel or on
80 or 40 megahertz
channel or an 80 megahertz channel, and especially 160 megahertz channel, it's
just harder to gain
access to that airspace.
And so even though when we do get access to it, we can communicate a massive
amount of
data, it makes it harder for a bunch of stations to reliably take turns.
We'd all rather be connected very reliably, maybe at a slower data rate, but at WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
We'd all rather be connected very reliably, maybe at a slower data rate, but at
least have
consistent access.
It's typically what we're going for in a high density design.
Now furthermore, we actually flip bonded channels on its head with modern
wireless techniques.
We have something called orthogonal frequency division multiple access or OFDMA
.
This was introduced to us with Wi-Fi 6, which from an IEEE perspective is 802.
11 AX.
OFDMA actually takes a 20 megahertz channel and divides it up. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
OFDMA actually takes a 20 megahertz channel and divides it up.
And suggests that hey, I might have four different stations transmitting on
maybe, let's say,
a quarter of this getting a little bit messy here, but we each get a slice of
the channel.
So now we're truly talking about multiple stations sharing a particular channel
at the
same time.
And so it truly is flipping it on its head and saying rather than combining WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And so it truly is flipping it on its head and saying rather than combining
channels to get
more throughput, we're going to divide up a channel to get less throughput for
the sake
of supporting more stations.
Another aspect to high density deployments is actually the use of 2.4 gigahertz
and 6 gigahertz
cells.
So I already mentioned the concept of multicell.
And multicell can have a single access point, have 2.4, 5, 5, and 6. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And multicell can have a single access point, have 2.4, 5, 5, and 6.
And there's all kinds of different configurations out there.
This is one of Cisco's high density types of access points, for example.
But do notice that we're talking about 2.4 gigahertz again.
And 2.4 gigahertz fell out of favor to the point that in Wi-Fi 5, which was 802
.11 AX, there
was no 2.4 gigahertz.
The thought process when this was developed was we need to get rid of this very
busy band.
It's very small, we can't bond channels, it's very busy, nobody needs 2.4 giga WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
It's very small, we can't bond channels, it's very busy, nobody needs 2.4 giga
hertz, so
let's go ahead and get rid of it.
The truly no support for 2.4 gigahertz using Wi-Fi 5 and 802.11 A.C.
So it's interesting that now we're bringing it back.
The 6, which is Wi-Fi 6, which is 802.11 AX, this says you know what, we're
going to allow
2.4 gigahertz again.
And the reason for that is because of this. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
And the reason for that is because of this.
And the fact that now we can start to divide up our wireless cells.
So now 2.4 gigahertz becomes something that is a tool again for us.
It's a tool in our tool belt.
6 gigahertz is the same way, we just have to keep in mind that 6 gigahertz
support is pretty
low right now.
But as we start to see more and more devices, more and more mobile devices,
laptops, tablets,
and all kinds of different devices start to support 6 gigahertz, we'll now we WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
and all kinds of different devices start to support 6 gigahertz, we'll now we
're going
to see that more devices can take advantage of that 6 gigahertz cell.
So by spreading our devices across all of these different bands and channels,
we're
going to maximize the number of stations that we can support in this given
space.
Now one last note is it has to do with something that Cisco has for us, which
is known as radio
resource management or RRM.
Radio resource management is the automatic management of our wireless space, WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Radio resource management is the automatic management of our wireless space,
especially
as it relates to the transmit power and channel selection for our access points
.
Cisco recognized a long time ago, hey, by having a centralized wireless
controller, the
wireless LAN controller, we can look at a complex environment with all kinds of
access points WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
access points
in here and overlaps and very often and very quickly evaluate this to say, hey,
it was
the wireless network changes over time, maybe we should shrink some of these
cells, maybe
we should expand some of these cells, maybe we should change the channel scheme
to make
sure that we have less contention in our network.
And RRM helps us to maintain that over the course of time.
Well, believe it or not, for high density deployments, Cisco recommends turning
off RRM. WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
off RRM.
We would want to actually disable this automatic provisioning of wireless
configuration in
the environment because it's so complex and so difficult that we don't actually
want
to change on a constant basis.
Instead, we want to be very intentional with how we deploy our multi-cell overl
aps, come
up with a non-overlapping scheme and stick with it over time.
Because we do run the risk in high density deployments of having signals WEBVTT X-TIMESTAMP-MAP=LOCAL:00:00:00.000,MPEGTS:900000
Because we do run the risk in high density deployments of having signals
overlapping more often,
with there being contention from one side of a room to another side of the room
, especially
if wireless stations are transmitting at a much higher power level than our
access points,
which can happen.
And so Cisco says, hey, let's go ahead and disable the automatic configuration
of all of that
and rely again on the static configuration that we create at the very beginning
of this
high density deployment.