Wireless is wireless, right?
We hear wireless all the time, most people don’t understand the difference between cellular and Wi-Fi, but as a Wireless LAN engineer – You should In this post we take a look at some of the differences.
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Wireless is wireless, right?
The data for this comes from one
of our Wi-Fi Questions project
trying to come up with evidence-based answers
and do some experiments
to see if we could get answers around Wi-Fi
This question and answer has to do with wireless,
we hear wireless all the time,
wireless, wireless, wireless
Yeah, but my wife doesn’t understand the difference
between cellular and Wi-Fi
You should
Let’s talk about some of the differences
First up
Cellular has per-packet charges,
and it’s all about ARPU (Average Revenue Per User),
they’re all about taking money from clients using
I mean, that’s their business model
LTE is the current technology we use there
Or we could go back, oh you know,
all the way to 1xRTT for data that way
These are always controlled by some central authority
not just the business, but the actual traffic flow
is controlled by a cell tower
Now, if you contrast that with Wi-Fi
Wi-Fi is uncontrolled,
it’s free, most situations totally free
It’s not driven by any central control
The protocol itself has to figure things out
Now we call that
Distributed coordinated function (DCF)
Now, that sounds really dumb, if it’s coordinated,
how can I coordinate it by distributing?
Well, what it is, is each of the individual devices
every transmitter, whether AP or client
all have to make a decision on when to transmit
and to try not to bother all the other neighbors
who are trying to transmit on the same frequency
So there’s a big protocol around
We call it the game or teaching classes
how a transmitter has to wait for dead air
then pull a random number
then countdown and then get access
and do preamble detect and energy detect
and all these things
to minimize the amount of collisions that take place
Because Wi-Fi is CSMA/CA – collision avoidance
we have no collision detection
Thus, Wi-Fi is not very efficient at all
As a steward of the minimum
we get of, you know, frequency
the spectrum that’s been to assign to us
we’re not really efficient at using it
LTE is extremely efficient
but they use an entirely different kind of protocol
So to prove this, we’re going to do some testing
Let’s talk about our testing
In this testing, what we wanted
our design goals – to be easy
repeatable, and you could do this
on your own with any device at all
We wanted a local test server and a remote test server
so that we could test the cellular
on the other side of a link, that’s our WAN test
and then test Wi-Fi only
which is our WLAN test
And we want anyone to be able to pull this off
so we wanted on any device
both to have local and on the Internet
And so what we ought to do was use a WLAN Pi
the WLAN Pi a little handheld single board computer
And one of the pieces of software
that’s running on a service
is from LibreSpeed
And it’s an HTML5 throughput tester
Now, later, there’s a slide that’s gonna show you
all the details that’s behind it
But just realized it’s going to run a jitter test
a ping test, a download, and upload and, different timing
and if you care, if you’re anal and you want to know
all the details, they’re available for you
And because it runs on lots of platforms
you can run it on Linux
or Windows or wherever you want
We just chose to put on WLAN Pi
because it’s simple, and it felt more like a device
that’s our target, our end target
and from the client side, all you needed was HTML5
and this runs on any current browser
and mobile browsers even
and it does each of those things I mentioned
So let’s look at our test setup
What we did is we are going to test a client
We actually tested four different types of clients
against four different types of access points
And then aggregated the data together
On the green path is our WLAN path
Client to AP, to a switch, directly to the WLAN Pi
that this connected to the switch
There was no traffic that went over the WAN
It’s all local
The red traffic is our WAN traffic
and it followed the same path
the client device to the access point to the local switch,
But then that switch was connected to a Mi-Fi
a cellular to Ethernet converter
that did that little work
By the way the site we used
there was a cell tower
within 100 meters of where we were
So very good cell connection
Now, in this picture, I called it Internet backhaul
because you could use this exact same technique
to test your backhaul
at home, at an office, anywhere you like
One of the devices
is to connect only to the AP to give you only wireless
And the other one is gonna be placed on the other side
of your Internet connection
Back at your home office
This one happened to be at a school district office
We were on a school district property
and this was in their office
But to get to it, it had to go out over AT&T Cellular
back in from the cellular network
back into where that was
So that was our test setup
The test tool look something like this
When you run it, it’s gonna do a five-second test
on ping and jitter, and it’s going to capture some data
for ping and jitter information
And you get the little speed dials as it do it
But it also shows a little history of how it happened
And then it goes through
a download cycle for 15 seconds
and an upload cycle for 15 seconds
So this takes about 30 seconds per test
And we did one test per client
against four different APs
So each client did four APs
Next client does four APs, et cetera
So we collected all that data
the graphs I’m going to show you
they were all aggregated back together
We do have the data for the individual ones
But for this demonstration to show the difference
between WAN and WLAN, the aggregation was fine
And I promise you the detailed slide
here’s the detailed slide
We’ll give you this slide
I’m not going to read through this
It’s just the details of the processes that took place
on the LibraSpeed engine that we were using
Now onto the results
In this evidence
again, aggregating four clients
against four access points,
the orangish-brown are
our distances across the football field
we went from 10 meters to 25 meters
to 50 meters, 75 out to 100
Note the numbers are pretty high here
The WLAN numbers
For all devices in aggregate, stayed around 60 meg
even all the way out to 100 meters away
So we’re doing kind of two tests
One test was what’s the difference between
cellular and Wi-Fi?
Wi-Fi beat the pants off cellular even at 60 meg
Now, I don’t know where you live in the world
but I know where I live
I have terrible cellular, if I can get 4 or 5 meg
I’m doing really good
In this test we pulled about an average of 12 meg
across the cellular network
Now, that could have been
bandwidth limited on AT&T site
But across the board, it stayed flat
Now, think about that for a minute
Hmm
The wireless LAN was fast
above 100 meg when we were close
and the cellular was capped
we lowered the WLAN and cellular stayed the same
We lowered the WLAN by going further away
and cellular stayed the same
Now, this would happen as we go
further and further and further out
Because, yeah, as the cellular was not our bottleneck
Perhaps maybe if we kept going, maybe the
I’m sorry, the cellular was the bottleneck,
our wireless LAN was not the bottleneck
And at some point if we kept going
maybe our wireless LAN would drop below the 12
and then the cellular would have matched that
But we didn’t go that far
We can use the same technique
the exact same technique, have a
Libre server
We happen to be running a WLAN Pi local
and one of across
So what if he didn’t have these
Well, what can I do?
You can use the same technique
to troubleshoot your Wi-Fi
WLAN alone vs WLAN plus Internet backhaul
those are the two things we are going to be testing
Now, the quick way to see this
is to check your MCS on your WLAN side
Now if you have a macOS you just hold the “option” key
hit boing boing boing
it will show you the MSC
If you have a Mac you can also run Adrian’s tool
to show you what it is (WiFi Explorer)
If you’re not on a Mac
you might have to look at a data rate
find the data rate, reverse engineer it
and look it up on an MCS table
But that will tell you what your MCS is
Well, it doesn’t really matter what your MCS is
If your data rate is high
you’re getting good throughput
through the Wireless LAN
If your Internet is slow and you have fast Wi-Fi
you don’t have a wireless problem
Now, if you don’t have the
Speed tests that we used
you can always go out and hit speedtest.net
and now it’s going to test your wireless connection
your firewall, all the way back to
wherever some Ookla server is
And I’ll give you a number
The example here I have was from a hotel I did in Dubai
The number I was getting was
867 on my wireless connection to the AP
MCS 9, I was maxed out
that was as fast as the APs could go
Yeah, my my MacBook could have went up
to 1.3 Gig
but the network was up at 867
should have been fantastic
But if you look at the speed test on that numbers
I was only getting 1 meg
less than that on download
I went to the office, talked to the manager
and he goes, “Why is everyone complaining?”
“We spent a $100,000 on our new Wi-Fi”
I said, “Your Wi-Fi’s fantastic
“It’s your Internet backhaul”
And he proudly said, “But we have an E1”
For those of you who aren’t, don’t do the international stuff
T1 was the US version, and it did about 1.5 meg
E1 did about 2 meg
So they had over 200 hotel rooms
and they were trying to share a 2 meg backhaul
Even after spending hundreds of thousands of dollars
on good Wi-Fi, great Wi-Fi
So if you ever need to use this, compare and contrast
your wireless connection to your
WAN connection to see where it is
Now, final question before I let you go
Will your WAN ever exceed your WLAN?
Think about it
Conclusion is, as long as your
Wireless LAN is exceeding your wired backhaul
Wi-Fi is good
The faster your wireless LAN goes – great
Another conclusion
you can take in freespace, a client,
even a iPhone off of an AP
100 meters away and still be pushing 60 meg
So when people go, “Well how far does Wi-Fi go?”
A long way
Thanks for listening
If you have any other questions send them on
and we’ll see if we can answer them in part of this series
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