They say “Change is the only constant”. With the advent of the 21st century,
the focus of telecommunication changed from voice, to highly profitable data-centric services such as
video streaming, file transfer, online gaming etc. In order to accommodate the sunami of data and
to accommodate the advancements, a new All Flat IP architecture
consisting of Radio called the evolved UMTS Radio Access Network or eUTRAN and Core called
Evolved Packet Core or EPC was adopted. Hello Everyone! Welcome back to the world
of LTE. In our previous videos, We have shown how development happened on the radio side in
LTE. In this video let’s try to understand the Evolved Packet Core with a real-life analogy.
Let’s Say Ross wants to fly in an aeroplane. Is Having a mere Ticket enough? No right !
Once reaching the airport, Ross needs to make sure that he is at the correct airline counter.
Because there are other airlines' counter as well. Ross identifies the correct airline counter from
its Seal. At the Check-In counter, Ross shows his ticket to the Officer. In addition to that,
he needs to prove that he is the actual holder of the ticket. He does so by showing his id card.
Once the authentication is done, the Officer issues the boarding pass using his ticket
information. From here on Ross doesn’t need to show his ticket, the boarding pass contains vital
information such as seat number, class, flight number, time etc. It is good enough to access
the aeroplane and other ground services such as rest lounge access, baggage collection etc.
There are other services as well such as Priority boarding, Bigger Better seats,
Fine dining, VIP Lounge etc. Based on whether Ross has a business class or an economy class ticket,
the services provided will be different. Or we can say the authorization to use priority boarding,
bigger better seats, fine dining, VIP lounges etc depends on the class. Once in the aeroplane,
the captain is in charge of everything and the Captain has flight attendants who provide
services to Ross. The in-flight services again depend on the class of Ross’s ticket.
So we can say, In order for Ross to travel, he needs to show his Personal ID
for Authentication of his ticket and the Class of the ticket such as Business
or Economy determines the services that Ross can avail. Now let’s compare Ross’s aeroplane travel,
with any user with a 4G enabled handset, who wants to latch to the network to use the services,
The information in the SIM card will help the user to connect to the correct service provider because
others are also providing similar services. Now, Similar to The Officer at the counter,
the MME will ask for identifiers from the User. Once the identifiers are provided, the MME
starts the authentication of the user by using authenticating details from the Home Subscriber
Server or HSS such as the XRES, RAND and AUTN. At the end of the authentication process, the
user is assigned a Globally Unique Temporary ID or GUTI. The boarding pass is equivalent to the GUTI.
From here onwards the GUTI will be used to avail all the services. Once the authentication is done
the User needs the authorization to use the services. The PCRF has the record of the services
that the user has subscribed to. Depending on this information the services such as
high or low bitrate, Allocation and retention priority, QoS Class Indicator etc are enforced.
This is similar to getting the info whether Ross is a business or an economy traveller.
Once on board, the Captain or the Serving Gateway also SGW is in charge of the services
and with the help of Flight Attendant i.e. Packet Data Network Gateway or PGW
serves the User. PGW gets the Subscriber profile from PCRF and enforces the services for the User.
After this, the user is able to browse the internet, make a voice call or use
other services such as playing video games etc. So, in a nutshell, the function of the EPC is
to First, Authenticate the User using the SIM card information.
Then based on the subscriber’s profile, authorizing the subscriber to use various services
such as internet browsing, voice or video call, play games etc. And to finally enforcing and
maintaining the quality of services during the usage. So, An ALL FLAT IP core network
helped in, 1. Reduction in the number of network elements, which greatly reduces the
Investment Capital(Capex) and Operational(Opex) costs. 2. A better flexible core network,
that can be well integrated with the legacy networks 3. A lower latency < 100 ms,
by ensuring QoS on each node of the data plane. Now This was just a simplified analogy.
There are various other functionalities that the nodes of the EPC take care-off which is
not covered in this video. In our upcoming videos, we will focus on the call flows. But before that,
we will catch a little glimpse of 5G. Happy Learning.