Architecture
When it comes to the network architecture for LTE you will often hear the abbreviation SAE (System Architecture Evolution) which indicates that all the network system architecture for LTE was evolved. The base station, called eNB, is directly connected to the core by the S1 interface. There is no network controller anymore as we had in CDMA so we have a much leaner architecture in LTE. The base stations are also interconnected to each other via the X2 interface.
The right figure shows in more details the functional split between the base station (eNB) and the evolved packet core (EPC). The EPC is composed by different entities: the Mobility Management Entity (MME), the Serving Gateway (S-GW) and the Packet Data Network Gateway (P-GW). The base station constitutes the evolved ULTRAN and also constitutes a radio access network.. It has functions for scheduling, dynamic resource allocation, measurement configuration and prevision, radio admission control connection mobility control, intercell radio resource management and more.
Figure: Simplified LTE Architecture
Figure: Simplified LTE Architecture