1. What is the Network Called?
The introduction clarifies that the entire LTE network is formally called the EPS (Evolved Packet System). It is designed as an End-to-End (E2E) All IP Network.
2. The “All IP” Concept
The Old Way (2G/3G): Two Separate Roads Before LTE, mobile networks had two completely separate “roads” (domains) for traffic:
- Circuit-Switched (CS) Domain: This road was exclusively for voice calls and SMS. When you made a call, a dedicated physical line (circuit) was reserved for you.
- Packet-Switched (PS) Domain: This road was for data (internet).
The LTE Way: One “All IP” Road The “All IP” concept means LTE abolished the “Circuit-Switched” road entirely.
- Everything is Data: In LTE, the network treats everything as an IP packet. It does not care if the data inside the packet is a voice conversation, a web page, or a video file.
- End-to-End (E2E): The document emphasizes this is “End-to-End”. This means the IP protocol is used from your phone (UE) all the way through the radio tower, through the core network, and out to the external server (PDN). There is no translation to “phone lines” in the middle.
3. The Two Main Components
The EPS is divided into two distinct parts:
- LTE (Long Term Evolution): This refers specifically to the Radio Access Network (E-UTRAN) technology. This is the “air interface” part that connects your phone to the tower.
- EPC (Evolved Packet Core): This refers to the Core Network technology. This is the “brain” of the network that handles authentication, mobility, and routing data to the internet.