UMTS, the architecture has two parts: the radio access technology, LTE, and the core network architecture - the Evolved Packet Core (EPC). As the saying goes, a beloved child has many names. So does the EPS. The terminology is slightly confusing. The whole system is named, depending on the source, 4th Generation (4G), EPS, or after the radio technology LTE. Especially in the popular press and marketing either 4G, or LTE is used. The EPS core network is called EPC, or also sometimes System Architecture Evolution (SAE). In this book, we will try to use relatively consistently the EPS terminology. When designing the EPS, 3GPP aimed to simplify the architecture, and make it more compatible with IP. Therefore, the new architecture is quite a bit different from GPRS architecture. The most important change in the new system is the complete lack of a traditional circuit switched domain. The telephony service is provided with a Voice over IP (VoIP) technology - the IP Multimedia Subsystem (IMS). In addition, the whole network architecture is also changed significantly. The EPS architecture is shown in Figure 2.10 [29]. If the differences between the 2G and 3G are in the details, between EPS and its predecessors it is the similarities that are in the details. The EPS network elements and their functionalities are listed in the following: Evolved Node B (eNodeB) is the LTE base station. However, it also includes some of the functionalities of the radio resource controller (BSC in 2G, and RNC in 3G). Therefore, there is no separate radio controller in the EPS network architecture. Mobile Management Entity (MME) is responsible for mobility management, authenti- cation, and authorization of the UE. The MME is practically a very similar element to the SGSN in UMTS. The difference between the 3G-SGSN and the MME is that the MME is only a control-plane element; it does not perform user-plane functions at all. Deploying IPv6 in 3GPP Networks S1-MME eNodeB LTE-Uu S5/S8 Evolved Packet Core Figure 2.10 EPS network architecture. Home 