The following schematic provides a good understanding of the overall LTE network infrastructure and elements. The Figure below describes the LTE & UMTS overall network topology, including not only the EPC (Evolved Packet Core) and E-UTRAN (Evolved UMTS Terrestrial Access Network), but also other components, in order to show the relationship between them.
The new blocks specific to Evolved UMTS evolution are EPC and E-UTRAN.
Other blocks from the classical UMTS architecture are also displayed, such as the UTRAN (the UMTS Access Network), the PS and the CS Core Networks, respectively, connected to the public (or any private) IP and Telephone Networks. The IMS is located on top of the Packet Core blocks and provide access to both public or private IP networks, and the public telephone network via Media Gateway network entities. The HSS, managing user subscription information is shown as a central node, providing services to all Core Network blocks of 3G and evolved 3G architecture.