 like LTE and SAE In this chapter we discussed some of the key 3GPP networks including the second generation (2G) GSM, the 2.5G network like GPRS, 3G network like UMTS, and 3G network extensions like IMS. The initiatives "Beyond 3G" taken up by 3GPP include LTE (long-term evolution) and SAE (system architecture evolution). The main difference between these two initiatives is that LTE is about enhancing the "access network" and SAE works on developing "core network" architecture to sup- port the high-throughput/low latency LTE access system. LTE is an effort to reduce the number of network elements, but offer higher data rates and better quality of service on a packet only network. It uses OFDM (orthogonal frequency division multiple access) for uplink and SC-FDMA (single carrier frequency division multiple access) for down link. LTE access network has two types of components (see Figure 9.9), the access gateways (AGW) and enhance node B (ENB). While the AGW does functionalities like mode management, data compression, and ciphering, the ENB works on all radio-related issues and mobility management. SAE is expected to provide an All-IP network solution with all services on packet switched domain and no circuit switched domain. It will support mobility with multiple heterogeneous access systems both supported by 3GPP like LTE and non-3GPP access systems like WiMAX. SAE consists of (see Figure 9.10): MME (mobility management entity): It does functions like user equipment authentication and mobility management. UPE (user plane entity): It manages and stores user equipment context, including ciphering, packet routing, and forwarding. 3GPP anchor: Mobility anchor between 2G/3G and LTE SAE anchor: Mobility anchor between 3GPP and non 3GPP Communication Networks LTE access network Figure 9.9 LTE simplified architecture. 3GPP anchor SAE anchor 3GPP access Non-3GPP access Figure 9.10 SAE simplified architecture. While the initiatives for next generation networks development are specialized domains, by separating the access 