LTE Overall Architecture with EPC Network Elements and Functional split between E-UTRAN and EPC
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.