y occur in the absence of the X2 interface between the old and the new eNodeBs). The EPC consists of several network nodes, where the control and user data plane are further separated (considering the architecture in UMTS/HSPA). The mobility-related signaling is targeted to the MME (mobility management entity), while the user data traf- fic from E-UTRAN toward the Internet and vice versa traverses through the serving gateway (S-GW) and the packet data network gateway (PDN-GW, or shortly P-GW), much like SGSN and GGSN in GPRS and UMTS in previous mobile generations. The main database in EPC is HSS, which contains user-related information, such as the subscriber's profile (e.g. services available to that user), as well as user authentication information. However, the main node in the EPC regarding QoS in the mobile network is the policy and charging rules function (PCRF). It was created as a software-based network node responsible for policy and charging control (PCC). The PCRF's goal is to detect the service flow and to determine policy rules for it in real-time, while enforcing appropriate charging policy for such service in the given mobile network. In the 4G architecture the PCRF provides PCC information that is required for bearer setup to the policy enforcement functions located in P-GW. 3GPP approved a new LTE marker for the LTE-Advanced specification in Releases 13 and 14, called LTE-Advanced-Pro. As the name says, it is fully based on LTE/LTE- 5 QoS for Mobile Ultra-Broadband Core network HSPA direct-tunnel HSPA+ architecture architecture architecture architecture NodeB NodeB NodeB eNodeB Radio access network Media (user plane) GGSN - Gateway GPRS support node Control (control plane) HSPA - High speed packet access MME - Mobility management entity P-GW - Packet data network gateway RNC - Radio network controller SAE - System architecture evolution SGSN - Serving GPRS support node Figure 5.3 Architecture evolution of 3GPP mobile networks. Advanced but with additional features. With such a professional versi