LTE Architcture and Components

[General Architecture - LTE-Advanced, Researchgate]

LTE (Long-Term Evolution) architecture, known as the Evolved Packet System (EPS), is a flat, all-IP network structure comprising three main components: User Equipment (UE), Evolved UMTS Terrestrial Radio Access Network (E-UTRAN), and Evolved Packet Core (EPC). 

LTE architecture eliminates circuit-switched components, using the E-UTRAN (eNodeB) for radio access and the EPC for high-speed, low-latency mobile data routing. 

Key Components of LTE Architecture:

1. User Equipment (UE): The end-user device (e.g., smartphone, data terminal) that connects to the network via radio waves. 

2. E-UTRAN (Evolved Universal Terrestrial Radio Access Network): The radio access network consisting of a single node type, the Evolved Node B (eNodeB or eNB).

• eNodeB: Acts as the base station, controlling mobile devices in one or more cells. Unlike 3G, the eNodeB handles both base station and radio network controller functions.
• Interfaces: eNodeBs communicate with each other via the X2 interface for handovers and to the core network via the S1 interface.

3. EPC (Evolved Packet Core): The core network responsible for mobility management, data routing, and session control.

• MME (Mobility Management Entity): Manages control plane functions, including user tracking, paging, authentication (with HSS), and security.
• S-GW (Serving Gateway): Routes and forwards user data packets, acting as the anchor for mobility between eNodeBs.
• P-GW (PDN Gateway): Connects the UE to external Packet Data Networks (PDNs), such as the internet, and performs IP address allocation.
• HSS (Home Subscriber Server): A central database containing user subscription information.

4. Key Network Interfaces

• Uu: Interface between UE and eNodeB.
• S1-MME/S1-U: Interface connecting E-UTRAN (eNodeB) to the EPC (MME/S-GW).
• X2: Direct interface between eNodeBs.
• S5/S8: Interface between Serving Gateway and PDN Gateway.