LTE Network Architecture
Figure 2 shows a very basic architecture of the EPS when the User Equipment (UE) is connected to the EPC over E-UTRAN (LTE access network). The Evolved NodeB (eNodeB) is the base station for LTE radio. In this figure, the EPC is composed of four network elements: the Serving Gateway (Serving GW), the PDN Gateway (PDN GW), the MME and the HSS. The EPC is connected to the external networks, which can include the IP Multimedia Core Network Subsystem (IMS). HSS Basically, the HSS (for Home Subscriber Server) is a database that contains user-related and subscriber-related information. It also provides support functions in mobility management, call and session setup, user authentication and access authorization. It is based on the pre-3GPP Release 4 - Home Location Register (HLR) and Authentication Centre (AuC). Serving GW The gateways (Serving GW and PDN GW) deal with the user plane. They transport the IP data traffic between the User Equipment (...