Do You Know The Difference Between Wi-Fi and Cellular?

by | Sep 16, 2020 | Blog

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.

https://youtu.be/yjWjSEUGPnk

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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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