In this lesson,
we're going to cover cellular connections.
Now, most of us have a smartphone in our pocket these days,
and we use cellular almost every day to connect
to the wide area network known as the internet.
Now, when we talk about cellular,
this includes not just our smartphones,
but also our tablets,
dedicated cellular modems for corporate networks,
or cellular wireless access points known as hotspots
or even fixed cellular service that we can get in our homes
and offices these days.
Now, there is a wide range of cellular technologies in use,
including older ones like 2G, 3G, 4G, LTE,
and the most modern version, 5G.
Whenever you hear somebody talking about the G,
like 4G or 5G, all we're basically talking about
is which generation of cellular technology is being used
by the cellular modem in that smartphone or other device.
Basically, for any of these devices to connect
to the cellular network,
they are going to have an embedded cellular modem
that supports one or more of these technologies
and the associated frequencies for them.
Now the first cellular networks,
which are now referred to as 1G,
were developed all the way back in the 1980s.
These 1G phones communicate using a frequency
of 30 kilohertz, and they had a bandwidth of about
two kilobits per second,
so they really weren't pushing a lot
of data over these 1G handsets,
and instead they were simply dedicated
to providing voice calls for the most part.
As time went on though,
cell phones moved into their second generation,
known as 2G during the late 1990s.
2G devices communicated over a GSM network
using the 1800 megahertz frequency band.
The big difference here is that 2G devices
ran over a digital network that used multiplexing,
and so it could start to use data
in addition to just providing phone calls.
Now the data was not super fast though.
Here in 2G we were talking about speed
similar to a dial up modem,
which was usually in the range of 14.4 kilobits per second
to 64 kilobits per second using the GPRS
or the general packet radio service.
In fact, when I started my first company back in 1999,
I had a 2G flip phone that I used
and I was able to tether it to my laptop
and use it to access the internet
and email invoices to my clients using this low speed
connection after I serviced their property
and I was back in my car.
Now, 2G gave us a lot of benefits with cellular devices,
even though those speeds were quite limited.
2G devices were the first ones to have SMS
and text messaging, as well as the ability
to use international roaming, conference calls
and the use of internet while away from our computers.
Another evolution in 2G was the introduction of the edge,
or enhanced data rates for GSM evolution,
which brought speeds up to one megabits per second
to most modern 2G devices, like the first iPhone
when it was released back in 2008.
Now the third generation of cellular saw the release of 3G
with faster data speeds.
At a minimum, 3G networks must support at least 144 kilobits
per second to be known as a 3G network,
but most devices were faster than that
and they supported speeds of around 384 kilobits per second
while moving in a car, or up to two megabits per second
if you are walking or standing still.
To provide these faster data speeds, 3G devices used
a wider frequency band with frequencies from 1.6 gigahertz
to two gigahertz being used within that 3G standard
depending on where you lived in the world.
Now there are three different technologies
that were actually used with 3G networks.
These are WCDMA, HSPA and HSPA+.
WCDMA is the wideband code division multiple access
that's used by the UMTS standard
and can reach data speeds of up to about
two megabits per second.
This is actually the slowest of all of the 3G technologies.
Now an improvement to WCDMA was called HSPA
or the high speed packet access standard,
and it could reach speeds up to 14.4 megabits per second.
This is sometimes referred to as 3.5G by the industry.
Over time high speed packet access evolution
or HSPA plus was released and this brought speeds up to
around 50 megabits per second,
and you'll sometimes hear HSPA+ referred to as 3.75G.
Now, the fourth generation of cellular saw the release of 4G
with even faster speeds and the introduction
of multiple input, multiple output, or MIMO, radio sets.
With 4G, we could get speeds of up to 100 megabits
per second while driving in a car
and up to one gigabit per second
for fixed stationary cellular modems
like you would use in your house.
4G devices even had a wider frequency band,
covering frequencies from two to eight gigahertz
depending on the implementation in your given country.
Now, when 4G first came out, it was often called 4G LTE,
Or 4G long term evolution.
These devices could actually reach beads of up to 100
megabits per second.
Over time, there was an improved version of LTE
called LTE Advanced or LTEA,
and this was an advanced version of LTE
that added more capabilities
and increased speeds of two to three times
that of a normal LTE, and under perfect conditions
when you're using a stationary cellular modem,
you could reach speeds of up to one gigabit per second.
Now, the fifth generation of cellular
is what we saw the release of 5G,
with faster speed and much more capability.
5G is actually pretty new, and its worldwide deployment
only began back in 2019.
5G devices bring an enormous improvement over the previous
generation's devices too.
With 5G, we can get speeds of up to 10 gigabits per second
using high-band 5G frequencies,
and this is one of the biggest differences
with 5G over the older generations.
5G is actually split up into three
different frequencies bands.
We have the low band, the mid band,
and the high-band frequencies.
Now the low band frequencies are between 600
and 850 megahertz
and they provide with speeds of only 30
to 250 megabits per second.
The benefits of using this low band frequency range though
is that it has a very long range
and can cover an area similar in size
to the older 4G networks.
The mid band frequency band operates between 2.5
to 3.7 gigahertz, and this higher frequency band
does support higher data rates of 100 to 900 megabits
per second, but each cell tower does cover less area
than that low band or a 4G tower could.
As of 2021, most 5G deployments were being done
using mid-frequency towers because it provides
a good balance of coverage with those higher speeds.
Now, the high-band frequencies operate between 25
to 39 gigahertz,
and this much higher frequency band does support extremely
fast speeds in the gigabit per second range.
The big challenge here though is that these frequencies
operate in millimeter wave bands
and this causes the range of those towers
to be much, much smaller.
Because of this smaller millimeter waveband,
the signal is also easily blocked by walls,
windows, and other objects.
For this reason, there's not a lot of high-band deployments
going on yet.
So far we're seeing these deployed near areas
where a lot of people are expected to crowd
into a small area such as near a sports stadium,
a amusement park or a convention center,
but otherwise, most people are still using
those mid-frequency bands.
Alright, I know I just covered a ton of facts
and figures for you when we talked about these different
generations of cellular technology,
and you are probably freaking out right now wondering,
"Do I have to memorize all these speeds
and frequencies for each one?"
And the answer is no, you do not.
Instead, you just need to know that the higher the G,
such as 4G is higher than 3G,
this means it's a newer standard and it has faster speeds
because that's pretty much what happened
each and every time.
The other thing that's important to remember
is that 5G comes in three different bands.
The low band that's used for further distance
but lower speeds, mid band, which has a good distance
and good speed and high band,
which has a very small distance, but very high speeds.
As you go upward in the band, you get faster speeds,
but you will decrease in your coverage area.
For this reason, you're going to find
that most 5G deployments are going to use those mid band
frequencies, which gives you a good amount of coverage
and pretty high speeds of between 100 and 900
megabits per second.
Now, in terms of cellular technologies,
they are going to operate in one of two
underlying technologies.
These are known as GSM and CDMA.
Which one you're going to use is really going to be determined
by which area of the world you live in
or which cellular provider you're going to be using
in your particular country.
For example, here in the United States,
if you're using T-Mobile or AT&T,
their services rely on GSM.
If you're using Verizon, they normally use CDMA.
If you live outside the US and you're working in Japan
or South Korea, they use CDMA,
but if you're going to be living anywhere else in the world,
most of the time they're using GSM.
So what exactly is GSM and CDMA?
Well, GSM is the global system for mobile communications
and it's a cellular technology that takes your voice
during a call and converts it to digital data.
Then your device is given a channel
and a time slot so the service provider can combine
your call with several other users' calls
to maximize the efficiency of their networks.
So, let's pretend they need to provide service
to four users simultaneously.
They could get each of us a quarter of a second
to transmit our digital data,
and then when it reaches the other side,
it'll be combined back together
and converted back into your analog voice so the person
who you're talking to can actually hear you.
This is actually a form of time division in the original
GSM standard, but it was modified
to different code division methods once 3G networks
were rolled out with GSM.
Now, CDMA, or code division multiple access,
is a cellular technology that uses, well, code division
to split up that channel.
For every call that's made, the data's encoded
with a unique key and then all the data streams
can be transmitted at once in a single channel.
On the other side, the receiver has the unique key
for each call to divide out the combined signal back into
the individual calls so the other side can hear just your
voice during your phone call.
Now, CDMA is actually a more powerful
and flexible technology than GSM is,
and that's why 3G GSM actually introduced
and adopted a lot of parts from CDMA method
and then termed it WCDMA, or wideband CDMA
or UMTS, the Universal Mobile Telephone System.
Now, which one is better, CDMA or GSM,
and which one should you use?
Well before 3G, 4G and 5G networks,
there really was a big difference
between these two technologies,
but ever since 3G was introduced,
we pretty much are all going to be using some form of CDMA,
even if you buy a GSM phone.
The only reason we really bring up this idea of CDMA
and GSM is so that you realize
that there is a difference in support
based on where you're going to live in the world.
As I said, GSM is much more widely supported
across the globe, so if you travel a lot,
you may want to carry a GSM supported
smartphone or hotspot with you.
Remember, it's always important
to check your cellular provider
for hotspot options in the areas you plan to work
out of mostly, or you plan to travel to.
Most smartphones can work
as a hotspot using either tethering
or an internet connection sharing over wifi,
but you can also purchase a dedicated mobile hotspot device
that is a cellular modem and a wireless access point
combined into a single small form factor device,
and I actually carry one of these with me wherever I travel.
Now the other major difference is that with GSM phones,
you have a SIM card to identify yourself to the network,
whereas with a traditional CDMA phone you don't
because CDMA devices are configured
and locked to your cellular provider.
For this reason, a lot of people prefer GSM phones
because you can simply replace your SIM card while traveling
and have a new local service plan for your phone
that's much cheaper than using your American plan overseas.
These days though, most modern smartphones also support
E-SIMs, or electronic SIMs where you simply download
an app from the app store and change your SIM
to a local provider to get the data service you want
as soon as you get off the plane instead of paying
those large international roaming fees
to your cellular provider back in the United States.