HSPA) are considered as part of the 3.5G network generation. 1xEV-DO used adaptive modulation and coding (AMC); it implemented Forward Error Correction (FEC) with higher code rates for better spectrum efficiency and an improved signal-to-noise ratio (SNR) to achieve a higher downlink rate of 2.4 Mbps. 1xEV-DO used only packet-switched data networks, unlike cdmaOne and cdma2000. HSPA covers both High Speed Downlink Packet Access (HSDPA) and high-speed uplink packet access (HSUPA), which improved upon the performance of 3G. HSDPA, widely known as 3.5G, improved the UMTS downlink rates by using AMC and improved scheduling algorithms to achieve a peak rate of 14 Mbps. HSUPA, widely known as 3.75G, used similar techniques with a dedicated data channel to achieve uplink data rate up to 5 Mbps. 4G was first deployed in 2009 in Stockholm, Sweden, and Oslo, Norway, using the LTE standard. Originally, the 3GPP 4G system was referred to as System Architecture Evolution (SAE), with a core network known as the Evolved Packet Core (EPC), and only the RAN was called LTE. How- ever, the LTE name became more popular, and the industry now uses it to refer to the whole system. As Figure 10-1 illustrates, 4G LTE has a core and RAN network that are completely different from the UMTS architecture. The 4G LTE EPC is fully packet-switched and does not support circuit- switched domains; in LTE even voice is carried as data using voice over IP (VoIP). Public switched (((2))) telephone network E1/T1 Voice Circuit-switch domain Voice Packet (((p))) Packet-switch E1/T1 domain NodeB network (((g)) Eth / IP Voice Packet SGW / MME Evolved eNodeB packet core network (((p))) Eth / IP Voice Packet gNodeB UPF/AMF 5G core network eNodeB: Evolved node B gNodeB: Nextgen node B BTS: Base Transceiver Station NodeB: Node B SGW: Serving gateway UPF: User Plane Function BSC: Base Station Controller RNC: Radio Network Controller MME: Mobility management entity AMF: Access & Mobility Management Function Figure 10-1 RAN Architecture-2G, 3G, 4G, and 5G The 4G 