- [Narrator] Let's talk about cellular radio technologies.
Originally, cellular phones used
the Global System for Mobile communications, or GSM,
to make voice calls and also used GSM as well as
the General Packet Radio Service to send data, that's GPRS.
And that would send data at 2G speeds
through the cellular network.
Nowadays, almost everyone around the world
can get 3G speeds, or anyone
who's really gonna be watching this video.
And so, extensions of those original standards were created,
the Universal Mobile Telecommunication System, UMTS,
and also EDGE, Enhanced Data Rates for GSM Evolution.
Both of those were used to attain 3G speeds,
but in a lot of areas in the world
especially in the United States and similar countries,
you can get access to 4G and 4G LTE.
Those speeds can be attained
only when the following is present:
the mobile device has to comply
with the International Mobile Telecommunications-Advanced,
or IMT-Advanced requirements.
The mobile device has to have a 4G antenna,
and it has to be in range of a 4G transmitter.
You have to have an actual 4G transmitter
on a cell tower nearby.
However, the fifth generation of cellular, or 5G,
is also available and is being deployed
as of the recording of this video.
And that's known as the ITU IMT-2020 Standard,
which can boast data transfer rates
up to 20 gigabits per second.
Now, are you gonna get those maximum speeds always?
No.
It depends on the device, depends on your location,
how powerful your device is,
how close you are to the cell phone tower.
Right?
So some of the radio technologies that you can have
for cellular devices, those are listed here.
Now, most devices cannot shut off
the cellular antenna by itself,
unless you shut down the device itself.
However, if you need to do that,
every device manufactured now
is required to have an airplane mode.
And that turns off any wireless antenna in the device,
including, especially, disabling the connection
to the cellular network.
It also disables WIFI and Bluetooth,
though you can turn those back on
after you turn airplane mode on.
Now, some devices can also limit
or disable cellular data usage, often known as mobile data,
but you don't really turn the cellular antenna off.
That radio is turned off when you put it into airplane mode.
So a little bit about radio and ID.
And there's some other terms
that you need to know for the exam.
For example, PRL.
PRL stands for, Preferred Roaming List.
This is used by cellular providers
that make use of CDMA networks,
that's Code Division Multiple Access networks
instead of GSM.
So what it is, it's a database that contains information
about the provider's radio bands,
sub-bands, service provider IDs,
or identification of those providers, and so on.
But if a phone uses GSM,
that technology and its radio functions
are controlled by a chip and a software package
that's collectively referred to as baseband.
Baseband updates are necessary
just like PRL updates if you're using CDMA,
but baseband updates are necessary
to communicate properly with GSM-based cell towers.
Baseband is also referred to as radio firmware
in that it controls network connectivity for GSM.
If a phone doesn't have access to a cell tower,
it won't be able to update either of these settings.
And so, the phone would at that point
have to be brought to an authorized service center.
And take a look here at this image.
We have the Status, which is usually within About Phone.
We have the status here for this device.
And it says, "Network unknown.
"Mobile network type, unknown."
And most importantly, "Service state, out of service."
This is not connected right now.
This is a device that has been taken off of
the telecommunication provider network,
the cellular provider network, I should say.
So, mobile network state, disconnected.
Now, that doesn't mean you can't use the device.
You could still use it with WIFI,
you could use it with Bluetooth, and so on.
You could send email.
You just are not gonna be able to do the normal things
you would do on a CDMA or a GSM network,
whatever this guy is part of,
you wouldn't be able to do voice calls and texting,
normal texting, at least.
All right.
And also note your signal strength
when you take a look at your connection.
You wanna check that as well.
Okay.
Now here we have another device
that is connected to the network.
And again, normally this is within the About Phone section.
And you see a lot of different information,
the phone name, the network type that you can tap on,
the status which includes the IMEI, identification,
battery, hardware info, software info, and so on.
If you do tap on Network, you'll get information like this.
So this phone is part of T-Mobile.
Our signal strength is negative 101 decibel.
Mobile network type, LTE.
So we know we're connected to 4G and LTE right now.
And in fact, it has a pretty good connection.
I've mentioned before in my lab here,
I'm very close to a cell phone tower,
far enough away for it to be safe as far as health concerns,
but very close.
And so, it can get a great signal.
And also it works well as a mobile hotspot
since I'm so close.
But we're in service and not roaming.
We are within service within our regular area.
And you also see the IP address information here.
So that's a little bit about the network.
You wanna take a look at all this stuff on your device,
see what you are part of right now.
You know, for example, you might go down,
you might get downgraded.
If you're too far from a cell phone tower,
you might get downgraded from 4G LTE down to 3G.
You might get downgraded to CDMA or GSM.
So, generally, what people are looking for
is the fastest connection possible.
So that's either gonna be 4G, 4G LTE, or 5G, nowadays,
as of the recording of this video.
Now, a couple other acronyms you should know,
and this has to do with identification.
IMEI and IMSI, these are both identification technologies.
IEMI, that stands for
International Mobile Station Equipment Identity.
And it identifies phones that are using GSM,
UMTS, LTE networks.
And you can find that ID number in your settings.
So for example, we would go on this device,
we'd go to our settings, General, About Phone, Status,
and then locate the IMEI.
I'm not gonna show my exact number,
but that's where you'd get to it.
On older phones, it's actually printed inside the device,
near the battery in some cases.
So, this is used to identify the device.
However, the other one, IMSI,
that's International Mobile Subscriber Identity,
that's used to identify the user.
Again, if you're working with GSM, or UMTS, or LTE networks,
this ID is loaded into the SIM card in most cases,
that Subscriber Identity Module.
That's the SIM card, Subscriber Identity Module.
That's that little card that you put in there.
We showed that before, that's your identification card.
You can't do anything with the phone without it.
For CDMA networks, the ID is loaded directly into the phone
or to a Removable User Identity Module,
which is similar to a SIM card,
but SIM card's are gonna be the most common out there,
especially in the United States.
So, to learn more, go ahead now and check out these settings
and cellular connectivity options on your smartphone.
And that's it for this video.