The main components of the

LTE network
 User equipments
Mobile phones, tablets, IoT etc.
 LTE eNodeB
 Core netwwork elements(MME, HSS, SGW and
PGW)

MME, HSS, SGW and PGW

These elements communicate with each other through interfaces,
such as S1 MME, S6a and others to set up signaling and session.

The communication starts with eNodeB and the UE requesting

Radio Resource Connection (RRC LTE). It goes all the way to the
core network components that exchange some messages with each
other. At the end of the call flow the UE establishes a successful
connection to the network through the GPRS Tunnelling Protocol
(GTP) and the buffered data will be passed to the UE LTE call flow
architecture.

LTE call flow architecture

 Radio Access Network (RAN)

eNodeB is the RAN of the LTE call flow. It is a part of the E-

UTRAN radio access network and is the component that allows
UEs to connect to the LTE network.

 Evolved Packet Core (EPC)

The elements of the Core Network that are part of this process
are:

› Mobility Management Entity (MME)

› Home Subscriber Server (HSS)
› Serving Gateway (SGW)
› Packet Data Network Gateway (PGW)
The LTE Call Flow process
 1.
Beacon (MIB, SIB)
Master Informations Block (MIBs) and System Information
Block (SIBs) elements allow UE to find and sync itself to
network.

 2.
Random Access Preamble (RAP)
Is the first message from the UE to eNB, to achieve uplink
synchronization in order to obtain the resource for the third
message.

 3.
Random Access Preamble Response (RAP Response)
Random Access Preamble response allows the UE to send
further messages.

 4.
Radio Resource Connection (RRC LTE)
The UE uses UL-SCH allocation message to eNodeB which
contains UE identity (typically S-TMSI: MMEC+M-TMSI) and
the establishment cause for the RRC connection.

 5.
Radio Resource Connection Setup (RRC Setup)

eNodeB sends DL-SCH message to the UE in order to create the

signaling radio bearer (SRB) . The message contains:
configuration parameters for uplink RLC, UL-SCH, Power Head
Room (PHR) and Uplink Power Control.
 6.
 PDN Connectivity
The UE sends a message to eNodeB which contains: RRC has
been completed, Initiate the Attach procedure as Non-access
stratum (NAS) payload and PDN Connectivity request.

 7.
Attach PDN request
eNodeB will send its first message to the core network passing
the attach request to the MME. This message is sent via S1AP
interface and it contains the initial UE message which includes:
the PDN Connectivity Request , the Tracking Area Identify
(TAI) and E-UTRAN Cell Global Identifier (ECGI).

 8.
Authentication request and info
The MME will reach the HSS will send the scurity tuple to the
MME containing K-ASME, AUTN, XRES and RAND.

 9.
Authentication response

The UE sends the Autch response value which was computed

from the key K, AUTN and RAND.

 10.
Security Mode Complete
Security mode command MME sends the encryption and
integrity protection algorithms and key selection identifier (KSI-
ASME). The UE response message back to the MME with NAS
ciphering and integrity protection.

 11.
Location update request
Acknowledgment message sent from HSS to MME that contains
PDN subscription contexts (EPS subscribed QoS profile and the
subscribed APN-AMBR).

 12.
Session request
Create session request message from the Mobility Management
Entity (MME) to the Serving Gateway(SGW) to create a GTP
tunnel.

 13.
Default Bearer Request
Serving Gateway (SGW) will send this request to Packet Data
Network Gateway (PGW), to create a new entry in its EPS bearer
context table and generates a Charging Id.

 14.
Default bearer response
The default bearer response from the PGW to the SGW will
contain PDN GW User Plane address, PDN GW TEIDs User and
Control Plane, EPS Bearer Identity and QoS. On the other hand,
PGW will also send Downlink data that will be buffered in the
SGW for now.

 15.
Session response
Acknowledgment message from SGW to the MME that indicates
the establishment of GPRS Tunneling Protocol for control (GTP-
C) tunnle.

 16.
Initial context setup request
MME will send eNB initial context setup message containing S1
interface context setup request, NAS attachement accept and
activate default bearer request.
  17.
RRC security mode
The eNodeB will reach the UE with RRC security mode message
with the AS integrity protection and encryption algorithms and
START parameters. The UE sends to eNodeB acknowledge
message that uses the newly activated keys to encrypt and
integrity protection.

 18.
RRC reconfig
eNodeB will send RRC reconfig to activate the default radio
bearer.

 19.
RRC complete
The next thing happening in the LTE call flow is that the UE will
send acknowledgment message and attach RRC LTE complete
(EPC Bearer Identity, NAS sequence number, NAS-MAC).

 20.
Data flowing

Now, the UE has successfully established a connection to the

network and the buffered data will be passed to the UE in the
Data Radio bearer.

Learn about EPC now!

Test and enable full LTE mobile

networks
 LTE Labkit
 ✔ Is an eNodeB for test that provides the full functionality of an
LTE network on your desktop.

✔ It is intended for mobile network operators labs that need

LTE test equipment for security tests. It can be used as a callbox
for IoT testing, M2M application developement and
manufacturing, mobile phone vendors and researchers.

 Minicore

✔ MiniCore is a core network which is mostly used for testing,

but can also act as the core network part of a mobile network for
under 500 users.

✔ It combines our YateHSS/HLR, YateUCN and YateSMSC in a

small package. It can be used a second core network for testing.
In a laboratory it can be paired with the LTE LabKit for a full
LTE/GSM network.
What is LTE?
LTE stands for Long-Term Evolution, which is a type of technology used for fast
mobile internet, like when you use your phone to browse the web or watch
videos.
It’s like a super-fast highway for data to travel between your phone and the
internet!

2. Main Components of an LTE Network:

Here are the main parts of the LTE network that help everything work:
User Equipment (UE):
This is your mobile phone or any device that connects to the LTE network.
Think of it like your "vehicle" that uses the LTE highway to send and receive
information.
eNodeB (Evolved Node B):
This is the cell tower that your phone connects to. It’s like a radio tower that
helps send and receive signals between your phone and the network.
It makes sure your phone stays connected to the network so you can make
calls or use the internet.
Evolved Packet Core (EPC):
This is the brain of the LTE network. It’s made up of different parts that help
handle the traffic and manage your connection.
There are several important parts of the EPC:
MME (Mobility Management Entity): It helps to find your phone in the network
and makes sure everything works, like a traffic controller.
SGW (Serving Gateway): This part moves your data between different parts of
the network.
PGW (Packet Gateway): It connects the LTE network to the outside world, like
the internet, and decides where to send the data.
HSS (Home Subscriber Server): This stores important information about you,
like your account details.
PCRF (Policy and Charging Rules Function):
This part makes sure you get the correct internet speed or quality when you
use data and helps with billing. It's like making sure everyone is paying the
right amount for using the internet.

3. LTE Call Flow (How Things Happen When You Use Your Phone):
Here’s how everything works together when you use your phone to make a
call or use the internet:
Phone Connecting to the Network:
When you turn on your phone and try to connect to the internet, your phone
sends a signal to the eNodeB (the cell tower).
The eNodeB talks to the MME, which makes sure your phone is allowed to
connect to the network (like checking your ID to make sure you’re allowed in).
Getting Ready for Data:
Once the MME knows your phone is allowed on the network, it tells the SGW
(Serving Gateway) and PGW (Packet Gateway) to set up the best path for data
to travel from your phone to the internet.
These gateways (SGW and PGW) act like bridges or roads for your data to
travel on.
Sending and Receiving Data:
After the pathways are set, your phone can now use the LTE network to send
data (like messages, web pages, or videos) and receive data (like downloading
files or watching videos).
The data moves from your phone, to the eNodeB, to the SGW, and finally to
the PGW, which sends the data to the internet.
Ending the Call/Session:
When you're done using the internet or end a call, the network closes the
paths and frees up resources so other people can use the network.
This is like ending a call and hanging up the phone when you're finished.

4. Testing and Enabling the LTE Network:

Before the LTE network can be used by everyone, it has to be tested and made
ready. Here’s how it’s done:
Planning:
Engineers make sure the network is set up in the right places, like placing
enough cell towers so you get good signal everywhere.
Testing:
They check if the LTE network works well in different areas by driving around
and testing how strong the signal is, kind of like checking if your phone works
in different places in your house.
Connecting Everything:
Engineers test the entire process: from turning on your phone to connecting
to the internet and making sure everything works smoothly.
Making the Network Available:
After everything works well, the LTE network is turned on and made available
for people to use.
Monitoring:
After it’s live, they keep an eye on how the network is performing and fix any
issues to make sure everything keeps running smoothly.

In Simple Terms:
The LTE network is like a big system that lets your phone talk to the internet.
Your phone is the vehicle, the cell tower is the road you travel on, and the
network’s brain (EPC) makes sure everything works.
Before the network can be used, engineers test it to make sure it’s ready for
everyone to use.