EPS provides the user with a PDN IP connectivity for Internet access and for the operation of services such as Voice over IP (VoIP). An EPS bearer is usually associated with a QoS. Multiple carriers may be set for a user, in order to provide different QoS flows and connectivity to different PDNs.
For example, a user might be engaged in a voice (VoIP) call while simultaneously performing web browsing or FTP download. A VoIP carrier could provide the necessary QoS for the voice call while a best-effort bearer would be suitable for surfing the web or FTP session.
The network must also provide for sufficient security and privacy for the user and network protection against fraudulent use.
This is achieved by means of a number of network elements which have different roles EPS. Figure “EPS network elements” shows the overall network architecture, including network elements and standardized interfaces. At a high level, the network is composed of NC (EPC) and E-UTRAN access network.
Although NC has many logical nodes, the access network is essentially consisting of a single node, evolved NodeB (eNodeB), which connects the values. Each of these network elements interconnected via standardized interfaces that allow multi-vendor interoperability. This gives network operators the opportunity to source various network elements from different vendors.
In fact, network operators can choose the physical implementation of the split or merge the logical network elements based on commercial considerations. Functional division between EPC and E-UTRAN is shown in the figure below.
LTE Overall Architecture with EPC Network Elements and Functional Split Between E-UTRAN and EPC
The LTE architecture is made up of two primary components: the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and the Evolved Packet Core (EPC). These elements work together to provide high-speed data and reliable connectivity for mobile devices.
E-UTRAN (Radio Access Network) includes the eNodeBs (evolved NodeBs), which are responsible for the radio communication between the UE (User Equipment) and the core network. The eNodeB handles tasks like scheduling, resource management, and mobility management. It also manages the physical and link layers, ensuring efficient transmission and reception of data over the air interface.
EPC (Core Network) is responsible for handling user data, mobility management, and connection management. The EPC consists of several key network elements:
- MME (Mobility Management Entity): Responsible for control plane signaling, including session management, security, and mobility (handover management).
- SGW (Serving Gateway): Acts as a data forwarding node between the RAN and the core network, handling user plane data and routing it to/from the UE.
- PGW (Packet Gateway): Provides connectivity between the LTE network and external data networks, such as the internet, by managing IP address allocation and routing user data.
- HSS (Home Subscriber Server): Stores user-related information and supports authentication and authorization procedures.
- PCRF (Policy and Charging Rules Function): Manages service quality and billing by defining and enforcing policies regarding data usage, QoS, and charging.
Functional Split Between E-UTRAN and EPC:
The functional split between the E-UTRAN and EPC defines the separation of tasks between the radio access network and the core network:
- E-UTRAN: Focuses on radio resource management, including the scheduling of user data, mobility management, and the connection between the UE and the EPC. It is responsible for managing the physical and data link layers.
- EPC: Handles session management, user authentication, data routing, and IP address management. It also manages QoS (Quality of Service) and mobility across different cells or networks.
Overall, the architecture ensures a seamless user experience by efficiently managing data flow, handling mobility, and optimizing resource usage between the access network (E-UTRAN) and the core network (EPC). The split of functionality ensures that the core network can focus on IP packet handling, while the radio network focuses on efficient wireless communication and user connectivity.