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- [Narrator] Let's talk about
cellular radio technologies.

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Originally, cellular phones used

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the Global System for Mobile
communications, or GSM,

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to make voice calls and
also used GSM as well as

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the General Packet Radio Service
to send data, that's GPRS.

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And that would send data at 2G speeds

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through the cellular network.

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Nowadays, almost everyone around the world

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can get 3G speeds, or anyone

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who's really gonna be watching this video.

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And so, extensions of those
original standards were created,

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the Universal Mobile
Telecommunication System, UMTS,

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and also EDGE, Enhanced Data
Rates for GSM Evolution.

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Both of those were used
to attain 3G speeds,

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but in a lot of areas in the world

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especially in the United
States and similar countries,

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you can get access to 4G and 4G LTE.

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Those speeds can be attained

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only when the following is present:

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the mobile device has to comply

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with the International Mobile
Telecommunications-Advanced,

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or IMT-Advanced requirements.

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The mobile device has
to have a 4G antenna,

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and it has to be in range
of a 4G transmitter.

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You have to have an actual 4G transmitter

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on a cell tower nearby.

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However, the fifth generation
of cellular, or 5G,

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is also available and is being deployed

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as of the recording of this video.

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And that's known as the
ITU IMT-2020 Standard,

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which can boast data transfer rates

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up to 20 gigabits per second.

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Now, are you gonna get
those maximum speeds always?

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No.

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It depends on the device,
depends on your location,

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how powerful your device is,

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how close you are to the cell phone tower.

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Right?

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So some of the radio
technologies that you can have

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for cellular devices,
those are listed here.

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Now, most devices cannot shut off

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the cellular antenna by itself,

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unless you shut down the device itself.

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However, if you need to do that,

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every device manufactured now

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is required to have an airplane mode.

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And that turns off any
wireless antenna in the device,

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including, especially,
disabling the connection

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to the cellular network.

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It also disables WIFI and Bluetooth,

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though you can turn those back on

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after you turn airplane mode on.

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Now, some devices can also limit

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or disable cellular data usage,
often known as mobile data,

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but you don't really turn
the cellular antenna off.

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That radio is turned off when
you put it into airplane mode.

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So a little bit about radio and ID.

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And there's some other terms

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that you need to know for the exam.

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For example, PRL.

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PRL stands for, Preferred Roaming List.

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This is used by cellular providers

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that make use of CDMA networks,

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that's Code Division
Multiple Access networks

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instead of GSM.

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So what it is, it's a database
that contains information

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about the provider's radio bands,

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sub-bands, service provider IDs,

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or identification of those
providers, and so on.

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But if a phone uses GSM,

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that technology and its radio functions

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are controlled by a chip
and a software package

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that's collectively
referred to as baseband.

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Baseband updates are necessary

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just like PRL updates
if you're using CDMA,

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but baseband updates are necessary

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to communicate properly
with GSM-based cell towers.

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Baseband is also referred
to as radio firmware

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in that it controls network
connectivity for GSM.

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If a phone doesn't have
access to a cell tower,

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it won't be able to update
either of these settings.

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And so, the phone would at that point

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have to be brought to an
authorized service center.

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And take a look here at this image.

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We have the Status, which is
usually within About Phone.

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We have the status here for this device.

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And it says, "Network unknown.

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"Mobile network type, unknown."

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And most importantly, "Service
state, out of service."

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This is not connected right now.

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This is a device that
has been taken off of

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the telecommunication provider network,

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the cellular provider
network, I should say.

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So, mobile network state, disconnected.

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Now, that doesn't mean
you can't use the device.

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You could still use it with WIFI,

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you could use it with
Bluetooth, and so on.

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You could send email.

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You just are not gonna be
able to do the normal things

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you would do on a CDMA or a GSM network,

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whatever this guy is part of,

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you wouldn't be able to do
voice calls and texting,

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normal texting, at least.

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All right.

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And also note your signal strength

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when you take a look at your connection.

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You wanna check that as well.

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Okay.

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Now here we have another device

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that is connected to the network.

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And again, normally this is
within the About Phone section.

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And you see a lot of
different information,

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the phone name, the network
type that you can tap on,

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the status which includes
the IMEI, identification,

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battery, hardware info,
software info, and so on.

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If you do tap on Network, you'll
get information like this.

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So this phone is part of T-Mobile.

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Our signal strength is
negative 101 decibel.

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Mobile network type, LTE.

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So we know we're connected
to 4G and LTE right now.

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And in fact, it has a
pretty good connection.

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I've mentioned before in my lab here,

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I'm very close to a cell phone tower,

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far enough away for it to be
safe as far as health concerns,

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but very close.

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And so, it can get a great signal.

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And also it works well as a mobile hotspot

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since I'm so close.

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But we're in service and not roaming.

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We are within service
within our regular area.

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And you also see the IP
address information here.

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So that's a little bit about the network.

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You wanna take a look at all
this stuff on your device,

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see what you are part of right now.

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You know, for example, you might go down,

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you might get downgraded.

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If you're too far from a cell phone tower,

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you might get downgraded
from 4G LTE down to 3G.

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You might get downgraded to CDMA or GSM.

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So, generally, what people are looking for

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is the fastest connection possible.

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So that's either gonna be
4G, 4G LTE, or 5G, nowadays,

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as of the recording of this video.

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Now, a couple other
acronyms you should know,

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and this has to do with identification.

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IMEI and IMSI, these are both
identification technologies.

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IEMI, that stands for

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International Mobile
Station Equipment Identity.

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And it identifies phones
that are using GSM,

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UMTS, LTE networks.

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And you can find that ID
number in your settings.

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So for example, we
would go on this device,

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we'd go to our settings,
General, About Phone, Status,

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and then locate the IMEI.

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I'm not gonna show my exact number,

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but that's where you'd get to it.

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On older phones, it's actually
printed inside the device,

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near the battery in some cases.

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So, this is used to identify the device.

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However, the other one, IMSI,

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that's International
Mobile Subscriber Identity,

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that's used to identify the user.

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Again, if you're working with
GSM, or UMTS, or LTE networks,

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this ID is loaded into the
SIM card in most cases,

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that Subscriber Identity Module.

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That's the SIM card,
Subscriber Identity Module.

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That's that little card
that you put in there.

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We showed that before, that's
your identification card.

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You can't do anything
with the phone without it.

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For CDMA networks, the ID is
loaded directly into the phone

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or to a Removable User Identity Module,

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which is similar to a SIM card,

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but SIM card's are gonna be
the most common out there,

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especially in the United States.

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So, to learn more, go ahead now
and check out these settings

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and cellular connectivity
options on your smartphone.

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And that's it for this video.