Hello Everyone!
Welcome back to the world of LTE.
Today we will start a new series on LTE Architecture.
Before we know the architecture we need to understand why do we need the LTE.
In this video, we will start with MAJOR REASON that gave rise to the need of LTE.
We will also discuss a little about the User Equipment before we can dive into the RAN
and Core parts in our subsequent videos.
The period of 2000 to 2010 saw a growth from 500 million to more than 4.5billion mobile subscribers
It was driven by user friendly and attractive devices such as iPhone in 2007 and Android
based smartphones which started from 2008.
Network operators had previously tried to encourage the growth of mobile data, by the
introduction of, flat rate charging schemes that permitted unlimited data downloads.
As a result of these networks started congesting in the years around 2010, leading to a requirement
of increase in network capacity.
The UMTS or 3G was a huge upgrade to GSM/GPRS or 2G.
But it was again facing some design limitations.
That’s why the governing body, 3GPP, decided to redesign the RAN and the Core Part.
For Example Specifying an Interface with a carrier BW
of 5Mhz in WIreless Code Division Multiple Access, was a bold step.
It performed well in limits but in practice it didn’t scale up very well.
We had discussed earlier that Higher the frequency means lower is the time between two transmission
steps which results in higher multipath fading.
That’s why Air interface was redesigned and OFDM was introduced.
where instead of spreading a signal over the entire band the data is transmitted over many
narrow bands of 180Khz.
As a result the attainable data rate compared to UMTS is similar for same BW but Multipath
fading is greatly reduced.
It also provides flexibility as LTE can have BW from 1.25Mhz to Upto 20Mhz which can be
further increased by Carrier Aggregation.
Thus providing more efficient BW utilization.
Now 2G/3G uses traditional Circuit switched core for voice and SMS, and Packet Switched
core for Data.
That means operator has to maintain two core networks simultaneously.
A major change in LTE was adoption of all-IP based core network.
Which means switching to VOIP or in this case Voice over LTE.
It greatly simplifies the design and implementation of Air interface, Radio Network and Core.
Quality of service mechanism on all interface ensures that Bandwidth and other requirements
of Voice Calls can be met even when the capacity limits are reached.
It is difficult to implement that’s why operators use Circuit Switched Fall Back to
2G or 3G for voice calls.
However operators are migrating to VoLTE as it is cheaper and more versatile.
With the advent of IOT devices the total number of connected devices is expected to reach
28 billion by 2021.
Now for these devices Latency is more important than bandwidth.
So a faster backhaul was need of the hour.
In LTE the maximum allowed delay is of the range 50ms to 300ms depending upon the QOS.
Also, all interfaces between network nodes in LTE are now based on IP, including the
back-haul connection to the radio base stations.
Again, this is a great simplification compared to earlier technologies that were initially
based on E-1, ATM and frame relay links, with most of them being narrowband and expensive.
Now you can see that major changes were done in the Radio Access Part.
but in order to access the Radio we need to have a device.
So before we can dive into the architecture let us understand the device used by an end
user.
In LTE Specification the Mobile Device is refereed to as User Equipment same as in UMTS.
The internal architecture of the user equipment for LTE is identical to the one used by UMTS
and GSM which is actually a Mobile Equipment (ME).
The mobile equipment comprised of the following important modules:
Mobile Termination (MT) : This handles all the communication functions.
Terminal Equipment (TE) : This terminates the data streams.
Universal Integrated Circuit Card (UICC) : Also known as the SIM card
The Mobile Termination and Terminal Equipment is basically the antenna.
In LTE the SIM Card can either- Run an application known as the Universal
Subscriber Identity Module (USIM).
A USIM stores user-specific data very similar to 3G SIM card.
This keeps information about the user's phone number, home network identity and security
keys.
It can also have ISIM module.
ISIM carry a lot of information used in SIP protocols such as your IP Multimedia Private
Identity (IMPI), domain, IP Multimedia Public Identity (IMPU) and cipher keys which are
used to encrypt information.
So, this application is used for SIP/IMS procedures - consequently, VoLTE calls.
So friends in this video we have seen what gave rise to the need of LTE.
We have also seen the functioning of User Equipment.
In our next video we will discuss the most complex section of the LTE Network Architecture.
Till then take care.
Happy Learning.