on the LTE mobile networks pointed toward addressing new markets as well as new functionalities to improve efficiency. Major novelties in LTE-Advanced-Pro include the following: Cellular Internet of Things. This refers to LTE enhancements for machine type com- munications (MTCs), which are targeted at definition of lower device category (Cat-0) in 3GPP Releases 12 and 13, with 1 Mbit/s in uplink and downlink. LTE device-to-device (D2D) communication. This is targeted at public safety as well as building a mobile network architecture for support of emergency services. LTE for V2X (vehicle-to-X) communication. This increases its importance starting from LTE-Advanced-Pro and then continues in 5G specifications. Low latency LTE. This is developed to enable new delay-critical services, which further continue their development in 5G. LTE assisted access. This is the approach to use the standardized LTE technology in unlicensed spectrum (on 5 GHz) for mobile data traffic offload or backhauling WiFi access points (APs). LTE, LTE-Advanced, and LTE-Advanced-Pro differ in maximum possible bitrates. LTE can use frequency carriers with different widths, including 1.4, 3, 5, 10, 15, and 5.1 Mobile Ultra-Broadband Network Architectures Operator IP services External IP networks (IMS, AS, etc.) Evolved packet core (EPC) Non-3GPP eNodeB eNodeB access access E-UTRAN User plane and control plane Control plane only AS - Application server MME - Mobility management entity GERAN - GSM EDGE radio access network P-GW - Packet data network gateway HSS - Home subscriber server PCRF - Policy and charging rules function E-UTRAN - Evolved UTRAN S-GW - Serving gateway ePDG - evolved packet data gateway UTRAN - UMTS terrestrial radio access network IMS - IP multimedia subsystem Figure 5.4 4G mobile network architecture for LTE/LTE-Advanced. 20 MHz carrier bands (wider carrier gives proportionally higher bitrate). For example, LTE-Advanced has higher bitrates due to the possibility for frequency carrier aggrega- tion on layer 2 (i.e. below the I